Anal. Chem. 1981, 53, 88R-142R (61L) Shimogata, M., Koyama, K., Ueda, K. Nippon Eiselgaku Zasshl(Jpn. J . M a . ) 1980. 35(1). 172: Pest. Abstr. 1980. 13. 80-1787. (62L) Sligh, J., Cochiane, W: P., Scott, J. Bull. Environ. Contam. Toxicol. 1979, 23(4-5), 470-4. (63L) Stewart, T. E., Cannizzaro, R. D. Chapt. 20 In "Pesticide Analytical Methodology", Harvey, J. Jr. and Zweig, G., Eds., ACS Symp. Ser. 136, American Chemical Society, Washington, D.C. 1980, 367-88. (64L) Tjan, G. H., Jansen, J. T. A. J . Assoc. Off. Anal. Chem. 1979, 62(4), 769-73. (65L) Vasundhara, T. S., Parihar, D. B. Fresenius Z . Anal. Chem. 1979, 294(5), 408. (66L) van Rossum, A., de Boer, F. G., Cannizzaro, R. D., van Mwrsehar, R., Stewart, T. E., de Wilde, P. C. Chapt. 10, in Vol. XI "Analytial Methods for Pesticides and Plant Growth Regulators", Zweig, G. and Sherma, J, ds.,
Academic Press, New York 1980, pp 227-46. (67L) Wells, D. E. Anal. Chim. Acta 1979, 104(2), 253-66. (68L) Wlslowska, E., Kostowska, B. Chem. Anal. (Warsaw) 1979, 24(4), 707-9, Pest. Abstr. 1980, 13, 80-0560. (69L) Wisson, M., van Hoek, C., Sauer, H. H. In Analytical Methods for PesticMes and Plant Growth Regulators"; Zweig, G., Sherma, J., Eds.; Academic Press: New York, 1980; Vol. XI, Chapter 8, pp 185-94. (70L) Woolson, E. A., Aharonson, N. J. Assoc. OM.Anal. Chem. 1980, 63(3), 523-6. (71L) Yu, T. C., Johnson, E. R., Montgomery, M. L. J . Agric. Food Chem. 1979, 27(6), 1413-4. (72L) Zakkis, L. H. Bull. Envlron. Contam. Toxlcol. 1979, 23(3), 391-7. (73L) Zanini, E., Barberis, E., Ronco, C. J . Agric. FoodChsm. 1980, 28(2), 464-6.
Petroleum R. E. Terrell Gulf Science & Technology Corporation, Pittsburgh, Pennsylvania 15230
This is the 15th review of analytical chemistry in the petroleum industry (1A-14A) sponsored by the Division of Petroleum Chemistry of the American Chemical Society. It covers, for the most part, papers abstracted in Chemical Abstracts, American Petroleum Institute Refining Literature Abstracts, and Analytical Abstracts (London) for the period July 1978 through June 1980. One area, asphalt, spans a 4-year period from July 1976 to June 1980. The format of the previous reviews has been followed in general. An input concerning improvin this format or the addition or Aletion of subsections woulf be greatly appreciated. The assistance of D. K. Albert, Standard Oil Co. (Indiana), Amoco Research Center, and C. A. Simpson, Mobil Research and Development Corp., in searching the abstracts is greatly appreciated, as is the additional screening and organization of the 16 authors of the following 11 subsections. The production of the review is due to their combined efforts.
methylenetetracosanic acid in the original source material (56B). Vorob'eva and others used GC MS to characterize the polycyclic Cl4-CZ6naphthenes o f t e 200-420 "C fraction of Siva crude oil. They also proposed a scheme for the formation of these compounds by the conversion of certain aliphatic hydrocarbons (88B). Grizzle and Coleman have reported a GC analysis for benzene and toluene in crude oil and other fossil fuels. The method employs two columns in series (OV-1 and TCEP), with provisions for back-flushing heavier material. Repeatability and accuracy are said to be f2% and f4% of the amount present (33B). Vo-Dinh has developed a method using room-temperature phosphorimetry for the rapid analysis of polynuclear aromatic compounds in fossil fuels (87B). Sultanov and others studied the content and distribution of nitrogen compounds in Baku crudes. The highest nitrogen content was found in the asphaltene fraction (76B). Mozzhelina and co-workers subjected West Surgut crude oil to acid hydrolysis and measured the resulting amino acids. Glycine and glutamic acid were the most abundant motein-derived amin'o acids (55B). Ferguson and Luke carried out a critical appraisal of flame photometric detectors for the determination of sulfur compounds. They discussed the problems of using a single FPD for the auantitative determination of trace level sulfur compounds in light naphtha, as well as using it for the qualitative comparison of the distribution of sulfur compounds in heavier fractions. Dual FPDs are also discussed (24B). Nuzzi and Casalini studied the variety of thio henic com ounds in the maltene fraction of the pentane Jeasphaltearesiduum of Kuwait crude (58B). Goncharov and others studied the phenols in eight West Siberian crudes and noted the trends in total phenol concentration and concentrations of individual compounds with increasing depth. They were unable to separate the effects of age and of temperature on these trends (3UB). Nametkin and co-workers determined the nature of the acids of normal and isoprenoid alkanes in diesel fuels and kerosines from a number of Baku and Mangyshlak crude oils (57B). Holstein and Severin concentrated carbonyl com unds from crude oils by extracting their complexes with irard-T reagent into water. The original compounds were recovered by acid hydrolysis and were separated by HPLC (44B). Brownrigg and Homing obbned total lurmnescence s of six topped crude oils, their vacuum distillates, anc/?i% residua and attempted to identify the principal emitting compound classes. They attributed the dominant fluorescence emissions to indoles and carbazoles, with weaker fluorescence coming from benzocarbazoles and three-ring aromatics. The
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CRUDE OILS F. C. Trusell Marathon Oil Company, Linleton, Colorado
The trend in this area toward analyses for a specific purpose (e.g., spill identification and geochemical studies) rather than characterization for its own sake continues unabated. Interest in syncrudes, as indicated by the number of references, is up sharply. Hydrocarbons a n d Hetero Compounds. Yashina and others used proton and 13C NMR techniques to study 22 Soviet crudes of a variety of com ositional types. The nalkane content, the degree of alip atic branching, and the extent of substitution on aromatic compounds were all calculated. Since the application of NMR is not limited by boilin range, such studies can be carried out on heavy fractions (%IB). Hajek and co-workers also studied Soviet crudes by use of 13C NMR (36B). Zhmykhova and Nekhamkina characterized three fractions of Marmovichi and Ladushkino crude oils boilin above 350 OC by mass spectrometry and predicted their ehavior as feedstocks for various refining processes (94B). Barabadze characterized the 350-500 OC fraction of Noriyskaya crude oil by IR and UV spectroscopy, calculating the contents of paraffins, naphthenes, and aromatic compounds (6B). Larskaya and others used GC and MS, ;e arately and in comof Sokolwa bination, to characterize the 200-500 arfo!(citn crude oil. They identified nearly 100 individual hydrocarbons (49B). Makushina and co-workers found the series o f ' 12methylalkanes (Cu-C30) and 13-methylalkanes (C26-C30) to be unusually abundant in East Siberian crude oils and proposed that these hydrocarbons are derived from 12,13-
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R. E. Terrell is Senior Project Chemist. group leader 01 the X-ray fluwescence $boratory 01 the Anaiyiical Technology DBpartment 01 Guit Science and Technology Corn pany. Pmsburgh. PA. He receive3 his B.S. degree in chemistry t o m Drexei UnbersW. Philadelphia, PA. He has had 20 years' experience wth anaiyiicai meLhcds using X-ray IiUOreSCenCe speCn0icq)y and 2 years wnh optical e m i s b n opctroscopy. Rior 10 joining Gull he was a member of me Inhared Spectroscopy Group 81 Penn Chemicals Research Laboratory, Philadelphia, PA.
%n
F. C. T~uIoII Marathon Oil Co. Littleton, CO
N. H. Fick
iexaco. 1°C Beacon. NY
PI. J. Lubeck Marathon Od Co
Littleton. C o
C. L. Kibbv Gull Resedrch and Development co.
Plttsbvrgh. PA
Gulf Research and bvebpment Co Pittsburgh, PA
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Byron Sudbir; Research and Oevslopment
Dept , CONOCO Inc. Ponca C@. OK
A
M. P. T. Bradley
Spectra-Physics Sanla Clara. CA
J. W. Loveland
Laramie Energy Technology
cenier Laramie. WY
Sontech, inc. Newtown Square. PA
J. D. Beardrley The Slandard Oil Co. (Ohio) Cleveland. OH
Gull Research and Development Co Plnsburgh. PA
J L Fabec Gull Science and Technolcgy Co
.. ... ... Suntech. Inc. Newlown Square. PA
ANALYTICAL CHEMISTRY. VOL. 53, NO. 5, APRIL 1981
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observed phosphorescence was attributed to naphthalenes (11B). Filimonova and co-workers have compiled an extensive literature review on the resin-asphaltene fraction of crude oils. A large number of properties were tabulated, and a tentative scheme for the formation and catagenic conversion of resins and asphaltenes was proposed (25B). Gottlieb studied the precipitation of asphaltenes from cyclohexane using n-alkanes of various chain lengths and in varying proportions to the cyclohexane. He has developed a stepwise precipitation of asphaltenes accordin to molecular weight (31B). Hajek and co-workers examinecf heavy crude oil residues by 13C Fourier-transform NMR. The short relaxation time of this nucleus in such residues permits pulse methods to be used for obtaining spectra without the addition of a relaxation reagent (37B). Syncrudes. “Analytical Chemistry of Liquid Fuel Sources. Tar Sands, Oil Shale, Coal, and Petroleum.”, is a compilation of 21 pa ers iven a t a symposium durin the Spring 1977 NationafAC8 Meeting (80B). Dooley an8 co-workers have published a review paper, with many references, of methods for characterizing syncrudes from coal (20B). Ulanovskii and others have reviewed various solvent extraction methods for fractionating coal liquids, liquid chromatographic procedures for further separation of the resulting fractions, and spectroscopic and chromatographic characterization of these concentrates (81B).Mair and Spitler have proposed an improved analytical method for coal liquids. The sample is chromatographically separated into h drocarbon and nonhydrocarbon fractions, and the hydrocargon portion is further separated into fractions containing saturates and aromatics with one, two, three, and four or more rings (53B). Paudler and Chepten studied the nitro en bases in solvent refined coal by GC/MS. They resolvet 150 different compounds and were able to identify 62 of them. They proposed some possible ways of removing some of the highly carcinogenic compounds (61B). Snape and others proposed a scheme for the assignment of 13Cchemical shifts. The scheme was used in the characterization of the asphaltene and aromatic fractions of a supercritical gas extract of a low rank coal and on the residue of oils obtained by hydrogenatin these fractions (73B). Yokoyama and co-workers anal zecffractions of oil obtained from coal hydrogenation by 13C&MR, proton NMR, and GC. Their interpretations of the 13Cdata were enerally confirmed by results from the other two methods (924).Dorn and others found that elemental C and H percenta es, as well as ratios of atomic ty es for these elements, coufd be determined in coal liquids y! 13C FT NMR. Better agreement with conventional analyses was obtained at 75 “C than at 32 “C, suggesting that certain solutions of coaly matter may be inhomogeneous (21B). Yan and others re orted that polynuclear aromatic hydrocar%ons could be letermined in coal liquids and shales without prior separation b dye laser excitation of Shpol’skii effect spectra. Calibration gy standard addition was suggested to overcome matrix effects (90B). Jackson and others compared the compositions of 11shale oils obtained by retorting as many different shales from the Green River Basin of Wyoming. The types of basic nitrogen varied significantly, but all other pro rties measured showed little variation between samples (&By Puxbaum and Leyden reported a simple routine method for the determination of organic and inorganic carbon in oil shale. Small samples (2-4 mg) are heated in oxygen, and the evolved C02 is trapped in 0.02 M NaOH, where it is measured by conductance. Results for a standard shale agreed well Hrlth the certified values (62B). Cotter and co-workers used the Paraho shale oil plant to determine what samples should be taken and what analyses should be run, to monitor the composition of air, water, product oil, and solids in, and around, a shale oil plant (17B). Siggia and co-workers have carried out studies on the characterization of shale oils by liquid and as chromatography. These include separation and anafysis of the alkane/alkene, aromatic, and polar classes (18B,22B) and the acidic and basic classes of compounds (79B).Rubin and others isolated the acidic and basic fractions from shale oils, as well as from other kinds of fossil-derived liquids, and described the similarities and differences observed (66B).Hurtubise and co-workers have reported a method for the isolation and 9OR
ANALYTlCAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
determination of benzo[a]pyrene in shale oil. The detection limit is approximately 1 ppm (45B). Selucky and others separated a sample of Cold Lake bitumen into seven fractions by conventional methods and then characterized each of these fractions. They concluded that this sample resembled Athabasca bitumen but contained more asphaltenes and less acidic and saturated components (70B). Bunger and others compared four bitumens from Utah and Alberta. The samples were fractionated by liquid chromatography, and the fractions were analyzed by conventional methods. Among other things, they reported these samples resembled Wilmin on crude oil in their hydrocarbon/nonhydrocarbon distri ution (12B). Zelenin and co-workers concentrated the oxygen-containin compounds from a 350-400 “C cut of shale oil and studie! their compositions by elemental analysis and IR spectroscopy (93B).Borwitzky and Schomberg identified more than 140 polynuclear aromatic hydrocarbons from coal tar. They suggest that coal tar is a very inexpensive, and very complete, mixture of these compounds (IOB).Glajch and others pyrolyzed coal tars and etroleum pitches and characterized the products by packefcolumn GC. They described a computerized data collection system which facilitates comparisons of samples (29B). Angelova and co-workers removed the organic matter from bituminous rocks by extraction and by heating. They compared the structures and functional groups in the products from each method (3B). Urov and Listrem extracted, and then hydrolyzed, the bitumens from shales of the Pripyat deposit in Belorussia. The hydrolysis products were studied by GC, TLC, and IR, and the compositions of the hydrocarbons and carboxylic acids obtained are given (82B). Geochemical Studies. Larskaya and others analyzed a series of Upper Vendian crude oils and related the differences in composition and structure to the composition of the organic matter from which they were formed and to the conditions occurring during hydrocarbon formation (50B). A study of 60 Paleozoic and Mesozoic oils, concentrating on measuring the steranes and pentacyclic triterpanes, has been reported. The samples were passed through a Florisil column to remove asphaltenes. The compounds of interest were further concentrated by silica gel chromatography and adduction and finally detected b GC/MS. The methods described can also be applied to se&ment extracts (7B).Bieri and others analyzed sediments from the Atlantic outer continental shelf for polynuclear aromatic and polycyclic aliphatic hydrocarbons at the ng/g level. They felt the PNAs were the result of pyrogenic input. They also discussed the relevance of (17a)-hopanes as indicators of petroleum (8B). Schaefer and co-workers have devised a sin le-step analytical procedure for the extraction and analysis ofhydrocarbons in rock samples. The crushed sample is placed in the flow stream of the gas chromatograph, where the carrier gas also serves as the stripping gas. Analysis time through C8 is 40 min (67B). Uspenskii and others evaluated the petroleum producing potential of rocks on the basis of the content and composition of their organic matter. The greater the content of lipids, the better their potential as source rocks (83B). Schmitter and co-workers used a variety of chromatographic techniques to separate high molecular weight carboxylic acids from crude oils. Analyses were carried out on the resulting concentrates by GC and GC/MS. Particular attention was paid to the acids of the hopane series because of their importance as biological markers in correlation problems (68B). McGowan characterized the acids produced by controlled potential oxidation of Green River oil shale kerogen with perchloric acid (52B). Robin and Rouxhet investigated the carbonyl and carboxyl groups in a series of kerogens from different sources by IR spectroscopy. They described differences in distribution and in total concentration and related them to differences in source material and maturity (65B). Castex analyzed some kerogens recovered from the Atlantic Ocean in the course of the deep sea drilling project. From their infrared spectra and their elemental composition he was able to classify them as being from a marine, continental, or mixed source (13B).Larter and others examined various kerogens by pyrolysis-GC/MS and used the results to assess the petroleum producing potential of the kerogens (51B). Abu-Elgheit and co-workers analyzed a series of crude oils for 14 metals by emission spectroscopy. They found that the
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total metal content decreased with increasing maturity and that ratios of certain metals were useful for roviding information on the age and origin of the oil ( I B f : Strand has roposed a method for the classification of petroleums anlrock bitumens based on their IR spectra. He demonstrated its utility by matching- petroleums to their _ parent bitumens (75B).- Oil SDills and Identification. Guiees has defined a set of specifications for equipment to moni’tor the hydrocarbon content of water discharged at sea. He has also described the various types of equipment available for this task and examined in detail those instruments which met his criteria (3523). Jones examined in less detail the analytical methods for identifyin the source of petroleum and its products which are spillefat sea (4713). Higashi and co-workers used GPC with an ultraviolet detector to distinguish between crude oils and several of their refined products. In cases where the chromatograms at 254 nm were similar, better differentiation could be obtained at 280 nm (39B). The found that the GPC profiles changed very little when cru& oil samples were artifically weathered, while the GLC profiles changed markedly due to the loss of light ends (41B). Ochi and Okaichi, however, found that the GPC profile of weathered crudes differed significantly from the respective unweathered crude, complicating identification (59B). Bonevski and Weber reported that crude oils could be distinguished from one another by plotting total fluorescences vs. temperature, using a 365-nm excitation source. While all oils examined showed a marked decrease in fluorescence above 375 “C, their behavior below that temperature was characteristic of each oil (9B). Eastwood and co-workers compared results from room-temperature fluorescence with seven other fluorescene or low-temperature luminescence methods for identifying fresh and weathered oil spills. The resultin spectra, and the instruments from which they were obtainel are discussed (23B). Rho and Stuart described a noncomputerized method for producing three-dimensional representations of fluorescence spectra. Such plots facilitate the comparison of fluorescence data from two samples (64B). Cheder and others discuss the use of organic marker compounds, both as internal reference compounds for quantitative determinations of pollutants and as qualitative indicators of certain types of pollution. Examples are given of each use, both for petroleum and for other classes of pollutants (14B). Frame and co-workers demonstrated the use of a nitrogen flame photometric detector in the identification of oil spills. A concentration procedure, which also eliminates spurious peaks from aliphatic hydrocarbons, was also described (26B). Clark and Jurs described a technique for digitizing gas chromatograms and then using a computerized pattern recognition routine to match oils. In a test using 80 chromatograms, 69 were correctly classified (15B). Utashiro and Matsuo used a specially designed gas chromatograph with a 0.3 mm X 10 m packed column to analyze the n-paraffins in crude oils and heavy fuel oils recovered from the sea (84B). Higaski and others have described their characterization of tar balls taken from the ocean using both conventional GC and sulfur-selective flame photometric detection (43B). They studied the effect of weathering on the samples and attempted to identify the sources of the tar balls (42B). Trace Elements. Antipenko and co-workers have reviewed the literature on the occurrences of trace elements in crude oil and have given some correlations between the trace element content and certain physiochemical characteristics of the oil and its distillate fractions (4B). They also surveyed the published methods for the separation and chracterization of petroleum porphyrins (5B). Giltrap and others explored spark source mass spectrometry with electrical detection as a technique for the determination of Al, Cr, Fe, Ni, Cu, and Sn in crude oils. It is less sensitive than photoplate recording but is faster and more recise (233). Gerasimova and co-workers reported that the aBdition of 3% Tic& to deasphalted crude precipitated the major part of all of the heteroatoms and trace elements except the sulfur compounds. They also noted certain correlations between the contents of various elements (27B). Studies of vanadium and nickel, and the various forms in which they occur, still attract considerable attention. Grizzle and co-workers made a critical evaluation of four AA tech-
niques for these metals and reported the advantages and short-comings of each (34B). Sebor and others have proposed a gel ermeation method for isolating nonporphyrin comp o u n z of Ni and V (69B), and Stejskal and others have developed a thermal diffusion technique for concentrating compounds of these metals (74B). Raghaven and Agrawal develo ed a spectrophotometric analysis for V and Ni said to be aEle to reach trace, and ultratrace, levels (63B). Shibata and others have described ESR studies of vanadyl complexes at temperatures up to 435 “C. They were able to calculate the activation energy for the interconversion of the two observed forms (71B, 72B). Laktos-Szabo described the separation, quantitative determination, and structural identification of V and Ni porphyrins from a series of Hungarian crude oils. The contents of these compound classes could be related to the geochemical classification of the oils from which they were recovered (48B). Nonroutine Characterizations. A book, “Chromatography in Petroleum Analysis”, describes the application of a wide variety of chromato aphic techniques to the analysis of petroleum and its p r o g c t s (2B). Paczynska-Lahme and Neumann investigated the structure of petroleum colloids by ultracentrifugation. They described the behavior of resins and asphaltenes and the effects of each upon certain properties of crudes and residues (60B). Weeks and McBridge were able to correlate the ease of hydroprocessing of 10 crude oils with the amount of heteroatoms concentrated in the . DreciDitates obtained from ultracentrifu ation (89B). gigashi and Hagiwara studied the effect of the pore size of the Dolvstvrene eel on the chromatomams of four different crude oils: Differekes in the chromat&gams of the same oil, as well as differences between oils, were observed and discussed (40B). Halasz combined a batch separation with silica gel and a column separation on the same absorbent to characterize a vacuum residuum (38B). Torradas and others described a procedure using distillation and column chromatography to obtain fractions from a crude oil. These fractions were then analyzed by GC, MS, IR, and NMR, to characterize the original crude (78B). Greenhow and Nadjdi described a nonaqueous titration for determining the acid compounds in strai ht-run and air-blow petroleum bitumens (32B). Csikai and AI-Hobori reported the a plication of an X-ray fluorescence analysis of sulfur and choride in crude oil, despite the fact that the peaks from these two elements overlap to a considerable degree (19B). Routine Characterizations. Vercier and Mouton discussed the development and principal technical characteristics of the new ASTM/CEN (Comite Europeen de Normalisation) distillation assay, and some of the controversy over this method (85B,86B). Mouton and Chelveder described a rapid, automatic distillation apparatus and compare results from it with results from conventional distillations (54B). Coleman and co-workers have tabulated results from the analyses of 800 crude oils from U.S. oil fields. Each oil is identified by field, location producing formation and age, and producing depth (16B).Torradas and Albaiges have reported on the composition of Amposta oil, a Spanish offshore crude ( 77B).
FUELS, GASEOUS AND LIQUID J. D. Beardsley The Standard Oil Company (Ohio), Cleveland, Ohio
Natural, Refinery, and Manufactured Gases. Kavan (43C) has developed a technique for sampling gases which consists of a pressure vessel containing argon. During transfer into smaller vessels, no condensation of higher hydrocarbons occurred and composition remained unchanged. A review of as chromatographic analysis of fuel ases with 29 references Ras been published by KO an and darkacheva (45C). Amerkhanov, Lychagin, and lidorova (3C) describe a chromatograph with three columns for the analysis of petroleum and hydrocarbon as mixtures. A patent has been issued to Burrough (118) for a method and compact analyzer to determine a selected gas in a gas sample. The apparatus has a radiation source (e.g., IR) from which a modulated radiation (at a first frequence) impinges on a flow-through sample cell. Olacsi, Balazs, Hoffer, and Egri (64C) have standardized the gas chromatographic analysis of natural gas with thermal conductivity and flame ionization detectors so that C I13 ANALYTICAL CHEMISTRY, VOL.
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hydrocarbons can be determined. In the separation of isotopic methanes by gas chromatography, Lukac (55C)has modified the surface activity of the glass capillary column to improve the R2/t ratio (where R is the resolution of an isotopic pair and t is the analysis time). After the column was etched, part of the surface was covered with a thin layer of active silica. Nitrogen plus helium were used as the carrier gas. Capezzuto, D'Agostino, Cramarossa and Molinari (14C) have studied the oxidation of methane with carbon dioxide, water vapor, and oxygen in radio-frequency discharges of moderate pressures. The reactor consisted of a quartz tube capacitively coupled with a 35-MHz radio-frequency generator. Mashbits, Okhotnikov, and Khokhlov (58C)have received a patent on the preparation of a gas sample for the chromatographic analysis of impurities contained in a gas. The process consists of passing the gas sample through a partition chromatogra hic column which sorbed the impurities; the c0ncentrateb)impurities were transferred to a carrier gas stream which leads into a chromatographic analyzer. Trace impurities in (permanent) gases and in natural gas have been determined chromatographically by Okhotnikov, Rotin, Khokhlov, and Yusfin (63C). An analyzer is described by Kas rowski, Jeziorowski, Adamczyk, Niesporek, and Bytom ( 3 4 8 for determining traces of carbon dioxide, carbon monoxide, and methane in gases. This analyzer is based on the change of an electrolyte resistance in an electrolytic cell with two electrodes. The apparatus and transistorized electronic accessory are described in detail. Vitenberg and Tsibulskaya (82C) have obtained a patent for the determination of trace impurities of aromatic hydrocarbons in gases by gas chromatography. Thompson (80C) discussed the anomalous behavior of the hydrogen signal during its as chromatographic determination in gas mixtures using a tierma1 conductivity detector and helium carrier gas. The direction of the signal is dependent on the hydrogen concentration in the carrier. The determination of methanol in natural gas has been accom lished by Lakeev and Vyalkina (51C) as follows: MetRanol was absorbed from natural gas by water and the methanol content of the aqueous solution was determined by photocolorimetry after treatment of the solution with chromotropic acid. A patent has been issued to Bakunin (6C) for the determination of trace elements in gases. The determination is based on obtaining condensation nuclei, activation of the nuclei (at 110-120 "C) obtaining a heated development agent vapor (a-aminovaleric acid), mixing the gas with the developing agent, development, and enlarging of the condensation nuclei. Mercury in natural gas has been determined by Orrit (65C) at levels of 1to 200 an8>20 a t 285 and 319 nm, respectively. A passing sample had UV absorbances of 24 and 21 at 285 and 319 nm, respectively. Adulteration by as little as 1% kerosine should be detectable. May and Mueller (59C) have made spectroscopic determinations of the temperature and hydroxyl concentration distributions in the combustion chambers of spark ignition engines. Gaseous emissions, unregulated exhaust components, and exhaust particulates were measured by Hare (30C) in dynamometer tests over eight operating schedules and five different fuels. A detailed description of the test program and results is given. A simple cryogenic unit for temperature programming from -50 "C is illustrated by deRuwe, Hein, Schulting, and van Grondelle (20C). An example of its use for separation of the components in car exhaust ases is given. Brown and Kroes (1OC)describe the design a n g o eration of metallic oxide semiconductor sensors for combusti&le gas and vapor monitoring. These sensors have been used in the determination of 50-100 ppm levels of lead-containing gasoline in air. Distillate Fuels. Simulated distillation by va or-phase chromatography has been applied to petroleum prducts from Cuban refineries by Gonzalez, Ibarra, and Perez ( 2 8 0 . Analyses of naphtha, kerosine, jet fuel, diesel fuel, and gas oil are discussed. Sauer, Jadamec, and Sager (72C) have attem ted to fractionate heavy fuel oils by means of reversecf phase liquid chromatographic columns at different temperatures. A review with 81 references is presented by Lang, Sebor, Kosina, and Kusta (52C) of nuclear magnetic resonance analysis of high molecular weight fuel samples. Altamirano, Cortex, and Cuevas (2C) have developed a twpstep method for the determination of n-paraffins (CB-C,,) in kerosine by molecular sieve adsorption and gas chromato raphy. Jet and diesel fuels which were prepared from oil shafe and coal syncrudes were examined by Antoine (4C) using as chromatography. The boiling range distribution was use to calculate various physical properties. Zrebov, Krasnaya, Postnikova, and Kalinin (87C) have evaluated the reliability of the determination of the aromatic hydrocarbon content of jet fuels by sulfonation with sulfuric acid. They concluded that the method was not reliable because the amount of sulfonated aromatics depended on the concentration of sulfuric acid. Phenols in kerosine have been separated and identified by Rossemyr (68C) using si1 lation and gas chromato aphy. Saint-Just and Larsen ( 7 0 6 have found a re1ationsEp between refractive index and the nitro en content of the hydrotreated products of a furnace oif from shale oil. Nitrogenous bases of straight-run and hydrotreated diesel fuels from an Arlan crude have been separated and identified by Baikova and Ben'kovskii et al. (5C). The separation was done chromatographically, and the compounds were studied by IR, UV, and mass spectrometry. Ward ( 8 3 0 presents a review of the historical development, performance characteristics, and applications of plasma as an emission source for inductively coupled argon plasma spectroscopy. Examples are given of the multielement spectrometric analyses of water, liver, rocks, stainless steel, and residual fuel oil. A spectrophotometric method using the reagent 2methyl-4-(2-thiozolylazo)resorcinolhas been developed by Gonzalez Dim, Gonzalez h a s , and Garcia Montelongo ( 2 9 0 for the determination of vanadium in fuel oil. This method is considered superior to the ASTM D 1548. Rossemyr (69C) has made a study of the cold flow properties and the response to a cold flow improver of some typical fuel oils. After column chromatogra hic separation, friction and wear reducing additives have 8,en determined by Kuehn, Stoecker, and Bor-
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mann (48C) using infrared spectrometry. Denisov, Kovalev, Borisova, Zvereva, Englin, and Slitikova (1912)have determined antioxidants in hydrocarbon vuels uantitatively. The sample containing the oxidation inh%itor is oxidized with air while being heated, and the induction period is measured. The antioxidant concentration is then determined from a calibration graph. To determine the amount of aluminum compound present as a lubrication additive in mineral oil or diesel fuel. D aev, Lozovaya, and Perveev (I7C) boiled the sample with p e r s o r i c acid, filtered the solution, and then titrated the diluted filtrate potentiometrically with sodium hydroxide. A technique in which a vidicon tube is used as a detector has been applied by Davis, Stockwell, and Pardue (18C) to the identification and determination of quinizarin in the eluant from a liquid chromatographic column. Quinizarin is sometimes added to a gas oil as a marker.
LUBRICANTS, OILS AND GREASES N. H. Flck Texaco Inc., Beacon, New York
Oils. The literature continues to reflect the increasing use of combination analytical techniques to achieve preconcentrationlseparation and identification/quantitationof components. Use of analytical instrumentation continues to predominate. Spectroscopic Techniques. Trawinski (710) described infrared (IR) spectroscopic procedures to determine hydrocarbon composition, content of additives, and thermal-oxidation stability of lubricating oils, and also published a review (700) on use of IR techniques for determining composition of lubricating oils and additives. Methods for determining olymethacrylate and succinimide additives in lubricating oils y qualitative and uantitative IR spectroscopy were developed by Vergos an! Stepina (730) Belafi-Reth ( 5 0 , 6 0 ) published two papers on determination of sulfde and thiophene sulfur compounds in lube oils by means of IR and UV spectroscopy. The sulfides were determined by IR measurement of the sulfoxides at 1040 cm-' after oxidation. An IR spectrometer interfaced to a computer was used by Lynch and Brady (400) to analyze for contaminants in complex oil mixtures, and Hannah et al. (270) described a technique using an IR spectrometer interfaced to a computer to determine small amounts of additives in lube oils. Preconcentration and se aration steps were described. Differences could be observezbetween new and used motor oils. The use of spectral coefficients, ratios between optical absorbances of characteristic IR bands, for calculating the contents of resins and paraffins-naphthenes in mineral oils was described in a paper by Shulova (630). Liquid Chromatography, Amos and Albaugh (10)published a review of various chromatography techniques employed for the determination of additives in lubricating oil, and Kajdas et al. (330) discussed at length the application of modern instrumental methods for determining lubricant com osition. The identification of amines in alkenylsuccinimigs, used as ash-free dispersants in motor oils, was investigated by Natoli and Peditto (460). Elution chromatography was used for the separation, and the purified cuts were hydrogenated followed by identification by gas chromatography (GC). Separation and characterization of aromatic hydrocarbons in mineral oils were reported by Mosescu et al. (420) who employed elution chromatography followed by UV s ectrophotometry of separated fractions. Kareher et al. (3407made a study to compare methods for determining aromatic and nonaromatic content of mineral oils boiling above 315 O C . The three methods evaluated were ASTM D 2549-68, DIN 51 38411975,and GUD 472175, each of which is based on elution chromatography. The application of several statistical (ndM, ASTM D 2140, and others) and instrumental methods (IR, UV, NMR) to structural analysis of mineral oil fractions was reported by Grzechowiak and Sztuba (250). A method for determining the hydrocarbon composition of petroleum oils by combined two-stage liquid chromatography and mass spectrometry is iven in a paper by Zakupra et al. (790). The analysis of alkyl and aryl zinc dithiophosphate lubricating oil additives was described in a paper by Fodor and Newman (180). Li uid chromatography was combined with infrared analysis (IF?) to obtain the alkyl to aryl ratio. Jamson and Hillman (320) performed this analysis by using high-
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ANALYTICAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
voltage zone electrophoresis carried out on a silica gel plate to which was applied the zinc-containing oil. For the characterization of the saturated components of mineral oils Szebenyi et al. (690) employed high- erformance liquid chromatography (HPLC) followed by GE) analysis of the separated fractions. High accuracy was reported, and only 30-70 mg of sample is required for the analysis. An HPLC procedure utilizing a dual IR UV detector system was used by Selucky et al. (570)for stu ying the composition of mineral oils and petroleum products. Interpretations of HPLC chromatograms are given. Majors and Johnson (410) reported on a high-performance exclusion chromatography technique using variable wavelength and refractive index detectors for separating additives of molecular weight less than lo00 from complex mixtures including lubricating oils. The analysis of engine oils with sizeexclusion chromato aphy was described in a paper by Wheals and Russell ( 7 6 0 y They included an illustration of a simple circuit which provides the first-derivative form of the chromatogram, thus facilitating comparison of chromatograms with ill-defined shoulders or inflections. The separation and characterization of hi h boiling and nonboiling mineral oil products were performed %y Halasz (260) using various HPLC techniques. He characterized the fractions by UV and IR spectroscopy and discussed sources of error and methods of preventing errors in liquid chromatography. The application of gel permeation chromatogra hy in refrigeration oil analysis was the subject of a paper y! Shiono et al. (610),and Shiono (620) re orted on the determination of poly(ethy1eneterephthalat.e)oEgomers in refri eration oils by a gel permeation chromatography recedef by an adsorption chromatography cleanup procefure. The evaluation of a refrigerant-refrigerator oil-metal (Fe and Cu) system was carried out by Enomoto et al. (140) with the aid of HPLC and gel permeation techniques. An improved method for measuring trace amounts of oil in diver's air sup ly was dee! variable scribed in a pa er by Sewell and Yee (590). T wavelength Ufdetector used with a liquid chromatogra h permitted a detection sensitivity of 0.2 pg. Baxa et al. ( 4 9 ) calibrated a liquid chromatograph with oil fractions of known molecular weight and demonstrated the suitability of the procedure for evaluation of the distillation ran e of lubricating oil fractions. Murui and Watanabe (430) pullished a review on the ap lications of HPLC to oils and fats anal sis. Karleskinfet al. (350) discussed the advantage of graJent elution HPLC on oils and fats analysis. For the determination of amine antioxidants in high-temperature jet engine lubricants Sniegoski (660) developed a uantitative thin-layer chromatographic '(TLC) method. T l e colored spots were measured by densitometry, and calibration graphs are given for additive concentration range up to 1%. Gas Chromatography and Mass Spectrometry. Antioxidant additives in lube oil were anal zed with gas chromatography by Kononyuk et al. (370). %he analysis of synthetic pentaerythritol ester oils by gas chromatogra hy-mam trometry (GC MS) was studied by &man et al. &ID)who K r m i n e d the atty acid composition of the oils after hydrolysis and calculation by computer of the theoretical isomer distribution of the esterified products. These authors (820) also analyzed trimethylol ropane-dipentaerythritol ester synthetic lubes by GC/Mff b ut reported the separation of isomeric trimethylolpropane esters was not successful. However, after separation by column chromatography, a detailed characterization of the complex ester s stem was possible by MS. Deo and Howard (120) used &/MS for the analysis of commercial aryl phosphate oils used as fire-retardant hydraulic fluids. For the analysis of lube oil fractions Severin (580) discussed photon-impact mass s ectrometry (MS) as an alternative to field ionization MS. h i s paper also covers the use of automated fragmentography for trace impurities analysis of saturated fractions. Mass spectrometry was combined with N M R b Chadha et al. (80) to analyze three white oils obtained by ocum treatment of lubricating oil base stocks. Oils in t h e Environment. The characterization of petroleum oils by high-speed gel permeation chromatography with UV detector was the sub'ect of a pa er by Higashi and Hagiwara (300). The method was ueefu in identifying the source of oil spills. These authors (290) also published a review of gel permeation, gas chromatography, and spectre
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metric methods for determining oils in the environment. Gottardi and Greiderer (240)also studied mineral oils in the environment and reported on a method employing combination IR and fluorescence spectroscopy. The identification of the source of a petroleum spill is based on use of a quotient (Q) which is specific for a particular substance and is related to the intensity of fluorescence (equal to the intensity of C-H vibration). Ochi and Okaichi (480)published a paper reporting on the fluorescence spectrometric determination of oil concentrations contained in seawater for up to a year after a refinery oil spill. Cook et al. (100)made a comparison of methods for determining traces of oil in water, Included were the EPA reference method 625 6-74-003,modifications of the EPA method, and the Horiba CMa-200 oil monitor (solvent extraction followed by IR at 3.5 pm). The EPA method gave the highest results on standards prepared from soluble oil in deionized water over the range 0-100 mg/L. Frame et al. (200)published an atlas of gas chromatograms of petroleum and synthetic oils. Included are descriptions of analysis techniques using dual flame ionization detectors and thermionic nitrogen-phosphorus detectors for GC fingerprinting useful in oil pollution studies. A review of fluorescence spectroscopic methods for oil spill source identification, including evaluation of each method’s utility for this purpose, was published by Frank (210). Other Analysis Techniques. The active ingredients of sulfonate additives were determined with dialysis techniques by Ifcsics (310)who reported the data agreed well with those developed by li uid chromatography. Shdiqul Alam et al. (600) develope! a differential pulse polarographic method which was suitable for detecting as little as 50 pM of zinc dialkyl dithiophosphate in commercial lubricant additives. in transFor the determination of 2,6-di-tert-butyl-p-cresol former oils, Foley and Kimmerle (190)used a method developed by Richards and Evans (510)which utilized pulse voltammetry. The method was rapid, accurate to *3% and sensitive to 10 ppm detection limit. The determination of total acid number of lubricants and additives was the sub’ect of a paper by Fernandez et al. (150). These authors used a microtitrimetric procedure with a high-frequency oscillator which was described by them in a previous publication (160).They also reported on further work (170)with this a paratus on determining total base number of new and usecflubricating oils. Sharp breaks at the end points were obtained and results were compared with those obtained potentiometrically. A method for the determination of chromium(V1) in synthetic and mineral emulsifiable oils was developed by Neustadt et al. (470).Separation is by TLC on alumina followed by spectrophotometric determination a t 540 nm on the water extracted relevant zone located by UV radiation. Lower limit was reported as 0.09 pg/mL. Clark and MacPherson (90) adapted the Orion NO, gas-sensing electrode to the determination of labile NOz- in unused cutting oils with a lower detection limit of 15 pg g. The moisture content of antifreezes and brake fluids was etermined with high precision by Nagashima and Hachiya (440)by measuring resistance while supplying power with an ac source. For the continuous measurement of residual concentrations (down to 0.5 ppm) of chlorinated solvents used in dewaxing lube oils, Von der Ohe et al. (750)described a procedure in which the solvents are stripped by passage of air and the vapors are passed to a measuring cell fitted with a flame ionization detector (to measure total hydrocarbons) and a halogen detector. Arutyunov et al. (20) reported on the determination of water in petroleum oils by extracting with ethylene glycol containing 2-propanol followed by GC analysis for water in the extract. Voloshchuk et al. (740)determined mercaptobenzothiazole and p-hydroxydiphenylamine additives in synthetic ester oils as a function of their optical density by photometry at 250-290 nm. Several investigators gave their attention to detection of trace N-nitroso compounds in petroleum metalworking products. Smyth et al. (650)examined metalworking cooling fluids by differential pulse polarography, GC, and thin-layer chromatography. They found only fluids formulated to contain high concentrations of di- and triethanolamines and sodium nitrite contained more than 0.5 pg/mL of N-nitroso compounds. Williams et al. (770)carried out the analysis of cutting fluids to detect N-nitrosodiethanolamine (I) semi-
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quantitatively by using a silica gel cleanup procedure followed by TLC on a silica gel plate. Further analysis of the trimethylsilyl derivative of I by GC MS gave results in good agreement with those estimated by C. The initial approach to this analysis by Kawano et al. (360)was different. These authors first decomposed the NO - in the cuttin fluid with urea and distilled the solvent under nitrogen. $he mixture was then silylated and subjected to GC with FI detector or GC/MS. The role of spectral selectivity in determining polycyclic aromatic hydrocarbons in oils by fluorescence detection for liquid chromatography is discussed in a paper by Ogan et al. (490).Their work compared two fluorescence detectors, a broad-band-pass detector with a 350-nm cutoff filter in the emission beam with the emission monochromator set to zero order and a narrow-band-pass detector with the emission monochromator used to select specific wavelen hs. The advantages of each mode are discussed. The an ysis of polychlorinated biphenyls in waste oils by HPLC with a reconcentration step by column chromatography was descriL d in a paper by Belliardo et al. (70). Used Oil Analysis. The analysis of used oils for the purpose of detecting contaminants, determining suitability for continued use, and uncovering potential equipment maintenance problems was the subject of apers by three authors. Simley’s (640)paper was a broa&r discussion of rograms primarily for mining machinery, while was devoted more toward spectrophotof:t%$%ypaper metric determination of trace wear metals and threshold concentration limits for given applications. Ohls (500)covered the use of inductively cou led plasma emission spectrometry, including the rotrode m&, for trace wear metals in used oils. The analyses were carried out on the oils in a direct way as well as after ashing, and the results were compared with resulb obtained by absorption spectrometry. A description of the ferrographic method for wear particle analysis was covered in detail with numerous illustrations in two papers by Rotondi (530,540).This technique for separating and studying particulate matter in used lubricants gives information on the condition of such wear mechanisms as aircraft gas turbines, gearboxes, transmissions, engines, and hydraulic systems. Ruff (550)used this technique along with filtration separation in his investi ation of uantitative methods in wear debris analysis in whch he injuded simulated wear debris (silica spheres, 3-pm iron particles, and 30-pm nickel particles). His pa r compared chemical analysis and particulate analysis and Ecussed problems of particle size resolution, lubricant dilution, particle overlap, and calibration of debris recovery systems. Properties of Oils. Sosulina et al. (670)measured the thermal stability of lubricating oils prepared from pentaerythritol esters by mass spectrometric determination of the intensity of oxygen-containing radicals through the degradation of the esters. A thin-film test for measurement of the oxidation of ester-type aircraft as turbine lubricants was developed by Cvitkovic et al. (Id).The procedure requires only 20-200 pL of sample placed in a depression on a catalytically active steel block heated in a stream of air. Analysis by gel permeation chromatography gives information on additive depletion and oxidized products formed. Dudukovic and Pejovic (130)compared an extended version of the IEC-74 method for testing the chemical stability of transformer oils and found it gave better precision for uninhibited oils than did the IEC-474 method. Bartz and Heckoetter’s (30)investigation of rapid bench tests for estimation of the detergent-dispersant properties of engine oils, including the Wolf test strip, PSW engine heating test, dispersancy bench test, and HD test (Fuhrmann, 1958), concluded that these rapid tests did not correlate with engine tests. The mechanism and activity of deter ents-dispersants, including succinimides, sulfonates, alkyf salicylates, and sulfurized phenates, was the subject of a paper by Zaslavskii et al. (800) who studied these additives in relation to their ability to disperse carbon black labeled with ’?I’isotope in lubricating oil. Heidemeyer (280) compared numerous methods for injecting air into water-Containing cutting oils for the urpose of studying their foaming behavior. Woodle (780)Beveloped empirical equations for estimating the characteristic factor of heavy oils from gravity in combination with kinematic viscosity, COC flash point, or aniline point.
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The calculations can be easily performed on a hand calculator having “ln” function. Greases. Fultz (220) presented a paper describing procedures using IR and high-speed gel permeation chromatography for identifying com onents of lubricating greases and the MIL specification to wkch they belong. The soap content of calcium complex greases was determined by a differential IR spectrometric procedure by Naqvi and Biswas ( 4 5 0 ) . Kozakova et al. (380)investigated the effects of solvent and heating period on hydrolysis in the determination of free acids and free bases in lubricating grease. Reverse-phase chromatography was the technique employed by Gorodnicheva et al. (230)to determine the mineral oil content of Li stearate greases. The compatibility of lubricating greases with elastomeric seals, with attention to analytical tests as methods which would not be affected by seal variability, was described in a pa er by Verdura (720). A system for measuring the color of rubricating greases was the subject of Sayles’ (56D)paper. He adapted a digital-reading reflection densitometer for this purpose and reported on its use in quality control. Stanton (680)reported on two round robin programs to evaluate test variables with the Falex I ring and block friction and wear test machine. Load was found to have the predominating effect in the first program, and the second program evaluated the effect of load on a variety of E P and non-EP greases.
WAX A. J. Lubeck Marathon Oil Company, Littleton, Colorado
Only a few papers were published in the area of petroleum waxes this review period. Of these, most dealt with finding the most appropriate techniques to characterize waxes for specific applications. Harmon (5E) used gel-permeation chromatography (GPC) and differential scannine calorimetrv to comDare and evaluate waxes used in elastom& compounding. Hk found the data from these tests were sufficient to enable him to select satisfactory substitutes for waxes used in compounding recipes. Sosa et al. (9E)reported on the GPC characterization of crude paraffin waxes containing different amounts of oil. The weight avera e and number average molecular weights were determinef from a calibration graph for n-alkanes and their ratio was found to be indicative of the broadness of the molecular weight distribution. An electron microscope was utilized by Szergenyi and Baumann ( 1 I E ) to examine macro- and microcrystalline waxes and fractions containing them. They verified the selectivity of molecular sieves in separating nparaffins from both isoparaffins and cycloparaffins. Two distillate waxes obtained from Ankleshwar crude oil tank bottoms were found to be predominantly n-paraffins by Agrawal and Joshi (1E).Their results based on physical properties correlation, isothermal gas chromatography, proton NMR, and 13CFourier transform NMR were all consistent with this conclusion. Galdina et al. (3E)used hotoelectrocolorimetry and thin-layer chromatography to letermine the content of aromatics in oxidized and unoxidized liquid paraffins separated from petroleum products by urea adduction. Szalka and Szergenyi (IOE)published a review, with 47 references, of the methods by which paraffins may be chemically and physically characterized. Mineral waxes from nonpetroleum sources were the subject of three papers of possible interest to those working with petroleum waxes. Bel’kevich et al. (2E) reported on the composition of the ethanol-insoluble fraction of the tar part of li nite wax. Preliminary separation on alumina forowed by 1% and UV characterization established the presence of normal and branched aliphatic hydrocarbons and oxygencontaining compounds. Ivanova et al. (6E)separated the acids and alcohols formed in the alkaline hydrolysis of gasolineextracted peat wax on an alumina column. Individual acids and alcohols in the fractions were then determined by gas chromatogra h . The chromium content of montan waxes contaminate: &ring their bleachin with chromates irl the presence of H SO4 was determined f y Maksimikhina et al. (8E). After t i e wax sample was burned, the product was treated with KC103, reacted with diphenylcarbazide and analyzed photometrically. 96R
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Khromykh et al. (7E) reported on the filtration properties of urea-alkane complexes formed during the dewaxin of petroleum fractions. In a similar study, the filtration cfaracteristics of paraffin suspensions in dewaxing and deoiling processes was determined by Gryaznov et al. ( 4 E ) .
ASPHALT James R. Couper Department of Chemical Engineering, Univershy of Arkansas, Fayettevi/k, Arkansas 72701
During the past 4 years, the major part of the research work has been devoted to compositional studies of asphalt. This review is arbitrarily divided into subheadings to facilitate the readability and location of information. There has been a significant decline in research activity during the past 4 years compared to the previous 2-year review period. Most of the research is now being performed by foreign investigators.
CHROMATOGRAPHIC METHODS Before a chromatographic separation can be undertaken, an initial solvent separation or preci itation step is performed. Fractions are obtained by various cLomatographic methods, and these fractions may be subjected to further analysis using IR, NMR, and UV spectrometry or X-ray diffraction. Gel Permeation Chromatography (GPC). Blanchard et. al. (6F)obtained 23 fractions by usin a preparation-type GPC technique from a Canadian asphalt. h e y used vapor pressure osmometry and NMR for further analysis. NMR analysis of some of the fractions showed that they were mainly aliphatic. The de ee of aromaticity resent in a given fraction, though slight, c k g e d with the morecular weight of the sample. Brule (15F),using GPC followed by differential refractomet and U V , noted that the polycondensed character of the asphytenes increased with molecule size. Boduszynski (12F) gave special attention to acidic and basic hetero compounds containing N and 0 in the as haltenes and maltenes, noting especially the association rog of the compounds in relation to the stability of colloidal systems in asphalts. Kiet, Blanchard, and Malhotra (47)extended the work reported earlier by Blanchard (6F),finding that aromaticity and naphthenic C content of fractions with intermediate molecular weights were low, while the paraffinic C content was maximum. The unit molecular weight of these fractions was 900, independent of molecular weight, indicating that the fractions are composed of a number of linked unit sheets rather than of a sin le, large pericondensed ring system. Brule (I6F)used 6 P C to qualitatively and quantitatively characterize asphalt, asphaltenes, and maltenes. The results provide an insight into the nature of associative rocesses involving these materials. Hall and Herron ( 3 7 8 , after a preliminary separation with pentane, subjected each fraction from several crudes to a preparative gel permeation chromato aphic technique. A comparison of the molecular size distriEtion was made. The found that most Kuwait maltene molecules were small enou to diffuse into the catalyst pores but that a substantial num%er of Kuwait al haltene molecules were too large. The effects of size distritution on thermal visbreaking and hydroprocessing were also discussed. Bockrath et al. (7F) characterized coal-derived asphaltenes by acid-base fractionation followed by GPC. Chromatography showed a broad distribution of molecular sizes in the solvent fractions; oil and asphaltene fractions were clearly distinguished despite some overlap. Schwager et al. (77F) separated and characterized synthoil asphaltenes by usin GPC and roton NMR spectrometry. A curve was developecfwhich may e! used to determine approximate molecular weights of coal liquid products. Boduszynski ( I O F ) used GPC on straight reduced and air blown asphalt to study the change in molecular size of asphalt components. He found that the formation of low-solubilit asphaltene aggregates occurred by hydrogen bonding a n i chemical reactions during the air blowing. Gas Chromatography. Gas chromatograph has been used to analyze tar phenols, petroleum pitch vo atiles, and native bitumens. Bermejo et al. ( 5 0 converted the tar phenols to trimethylsilyl ethers before subjecting them to gas chromatography. No column gave complete resolution of the phenol mixtures but nearly all were suitable for analysis of industrial mixtures. Greinke and Lewis (34F) used a com-
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bination of gas chromatography and UV and mass spectroscopy to identify volatiles from petroleum pitches in the environment, Douglas and Grantham (25F) used fingerprint chromatography to identify hydrocarbon constituents of bitumens, fossil resins, and asphalts. The fingerprints could be related to changing depositional environments. Inverse as chromatography (IGC) was used by Boduszyn~ki et al. (118to study the relation between asphalt group composition and the retention volume of standard substances. Tokareva et. al. (93F) used IGC to study fractions from a Russian petroleum which included the asphaltenes, oil-resinous fractions, carbenes, and carboids separated from them. The presented the coefficients of interaction of the sorbates u s e l as standards and the analyzed fractions. Refractive indexes of the standards are given. He also discussed the differing behavior of the standards and low asphaltenes, carbenes, and other heavier fractions. Pyrolysis gas chromatography was performed by Ramljak e t al. (73F) on bitumens. The characteristic ratio of light unsaturated and saturated hydrocarbons in bitumen pyrolyzate was used to determine the maltene and asphaltene fractions. A furnace-type microreactor was used for the pyrolysis. The authors believed that the results obtained by pyrolysis for asphaltene content of bitumen gave a more accurate analysis than the Institute of Petroleum method. Dubonska et al. (29F) used pyrolytic gas chromatographic techniques to determine minute quantities of bitumen in geology and mineral processing. Kugucheva et al. (52F) reported the gas chromatographic study of a heavy pyrolysis tar. Liquid Chromatography. Simple liquid chromatography was used to separate acids from asphalts as reported by Ramljak et al. (72F). An Athabascan bitumen was submitted to liquid chromatography followed by gas chromatography or spectroscopy (81F). The net result of this study was a multitude of fractions. The alkane content of the maltenes was low, the saturated fraction was about 90% polycyclic compound, and the aromatic fraction contained alkyl-, nahthenyl-, and dinaphthenylbenzenes in a 1:1.7:1.3 ratio. uwafag and Neumann (6IF)separated a bitumen from the Kirkuk field into alkanes, mono- and bicyclic aromatic, naphthenic aromatic, polycyclic aromatic, and heterocyclic compounds. The last were separated by ion exchange into acidic, basic, and neutral compounds. The alkanes were separated with urea, thiourea, and activated charcoal into fractions with varying degrees of branching. Vercier et al. (94F) developed an analytical chromatographic scheme which uses either a “slow” or “rapid” separation procedure to separate asphaltenes and resins. This scheme is presently used to monitor a pilot operation for upgrading residua oils. Schwa er and Yen (78F) separated and characterized coalderivecf asphaltenes by using a rapid chromatographic method. The study further used ESR to determine the nature of the association between asphaltene molecules and concluded that if charge-transfer interactions are present, they appear not to be significant as binding forces between the asphaltene molecules or nuclei. Selucky et al. @OF) used high-pressure liquid chromatography (HPLC) to se arate Canadian asphalts. The results showed that in Athagasca bitumen, strai ht chained hydrocarbons and olefins are virtually absent; Eoaever, n-alkanes are present in a Cold Lake bitumen fraction separated by molecular sieve adduction under the same conditions. HPLC techniques are particularly suitable for the study of the conversion of residua and tar sands bitumen to useful products, according to Drushell (27F). The results of this study are compared with compositions determined b the large scale clay-silica el separation technique. Dark aniMcGough (23F) used HPL!! to study the characterization of asphalt fractions. Their results were compared with analyses by GPC. Miscellaneous Chromatographic Methods. Gimpelevich and Ilina (33F) used paper chromatography to study the aromatic components of bitumens and petroleum. The method was most effective when used in conjunction with the spectroscopic identification of aromatic hydrocarbons, especially the method of quasilinear spectra. Bodzek et al. (14F) used laser chromatography followed by IR and high-resolution mass spectrometry to identify heterocompounds present in asphaltenes from various products of coal hydrogenation.
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Boduszynski et al. (12F) used ion-exchange and adsorption chromatography for the separation of maltenes. Acidic and basic fractions were both concentrated in the polar aromatic fraction as determined by adsorption chromatography. Kiselev’s @OF) research was continued with identifyin the acidic and basic components in petroleum- and coal- erived asphaltenes using ion-exchange chromatography. The acidic fractions had more complex chemical compositions and were characterized by using high-resolution mass spectroscopy. McKay et al. (57F) used an n-C6HI2asphaltene prepared from a California crude, separating it into fraction of acids, bases, neutral compounds, saturated and aromatic hydrocarbons using ion-exchange, coordination, and adsorption chromatography. The asphaltene is a complex mixture of the most polar and highest molecular weight compounds of the crude oil. Kawahara (44F) used electron capture detection gas chromatography as a fingerprinting technique to identify trace organic components in spilled asphalts. Albau h and Query (IF) used exclusion chromatography with muftiple detectors to follow com ositional changes of petroleum residuals during catalytic esulfurization. Selucky et al. (82F)conducted a detailed analysis on a Cold Lake Alberta asphalt using series of chromatographic separations followed by IR, UV, NMR, and mass spectrosco y. The composition of Cold Lake bitumen closely resembled of the Athabasca bitumen except that its asphaltene content is somewhat lower and its acidic and saturated content is sli htly hi her. kalasz f36F) separated vacuum residues from a Kirkuk petroleum using extrographic means. Bockrath et al. (SF) characterized asphaltenes isolated from a coal-derived li uid using sequential election by solvent chromatography (SEIC). The characterization study was used to uncover the chemical factors that influence analytical determinations.
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NMR, ESR, EPR, AA, UV, IR, AND X-RAY
METHODS Yamada et al. (96F)reported a comparison of various structural analyses for pitch fractions using a combination of NMR and X-ray diffraction methods and checked b a computer technique. The results obtained by the comhnation method were in good agreement with those obtained by the computer method. This implies that both methods are available for the structural analysis of such carbonaceous materials as pitch and coal extracts. Bartuska et al. (4F) developed a sophisticated NMR technique with the goal of providing high-resolution NMR spectra on solids with direct applications to bitumens. Posadov et al. (7OF) used NMR, IR, and UV to study the structure of petroleum asphaltenes. Highly substituted twoand three-ring aromatics in naphthenic structure were prominent. Sebor et al. (79F) used NMR spectroscopy to characterize an asphalt-resin fraction. The aromaticity increased from maltenes to asphalt to asphaltenes with increasing fraction molecular weights. Structural parameters for all fractions were tabulated. Hajek et al. (35F)analyzed heavy crude oils using Fourier transform NMR spectroscopy. They determined the amounts of aromatic and aliphatic carbon in heavy crude oils containing parama netic ions (e.g., ferric iron). These ions have an effect simifar to the addition of a reducing reagent. Kasahara (4IF) studied the structural deterioration of asphalt on hot storage using hi h-resolution Nh4R. Condensed aromatic rings appeared to %e unaffected by hot storage in the case of aromatics and resins but the ring number increased from 7 to 11in the case of asphaltenes. Takegami et al. (89F) conducted a structural investi ation of asphalts and their fractions using proton and carlon-14 NMR spectrometry. From relative intensities of the peaks.,the -ylene chain in these samples was deduced to be longer (Le., n > 12) than re orted previously. Dereppe et al. (24F) developed a methozusing carbon and proton NMR spectroscopy to derive a series of parameters of an “average molecule” which characterize complex multicomponent organic mixtures such as asphaltenes and heavy petroleum products. Pearson (67F),using wide line NMR to determine proton types in coal tar and petroleum pitches, reported that the second moment was a measure of aromatic protons. High-temperature proton NMR was reported by Yokono et al. (99F) on ethylene-tar pitch. Pyrolysis ANALYTICAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
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depolymerization and polycondensation can be monitored by the high-temperature technique. Podobaeva et al. (69F) used a Samotlor crude in their structure study of asphaltenes. Asphaltene samples were analyzed by a variety of analytical methods, NMR, gel ermeation chromatography, mass spectroscopy, and E S 8. Structures for fragments of asphaltene molecules were proposed. The effect of asphaltenes on the conversion of bitumens by hydropyrolysis was reported by Bunger et al. The primary analytical method to characterize the asphaltenes was NMR. An electron spin resonance (ESR) study of free radicals in Athabasca asphaltenes was performed by Niizuma et al. ( 6 3 0 . It was concluded that the temperature dependence of the absorption is due to stable polycycloaromatic doublet- and triplet-state radicals. Fuiseth et al. (32F) reported an ESR characterization of asphaltenes formed during the aging of coal liquids. A mechanism involving condensation of small heteroatom-rich molecules for insolubles and asphaltenes in the presence of ox gen was proposed. Chernova and Cgurkerashivli (21F) used an EPR method for studying asphaltene structure fractions of petroleum asphaltenes separated with the more polar solvents having higher contents of paramagnetic centers. Ma and Presley (56F) studied the vanadium content of asphak using flameless atomic absorption spectroscopy. The method can also be used for metals other than those (e.g., Cr and Hg) lost in ashing. Felscher ( 3 0 performed a characterization study of aromatic bitumen fractions with a special application of UV spectrometry. It was possible to calculate the contribution of naphthenic compounds to the monocyclic fraction, as well as the mean molecular weight of the fraction. Infrared spectroscopy was used by Filimonova et al. (31F) on the composition and structure studies of petroleum asphaltenes. The asphaltenes were 50-78% aliphatic. The aromatic portion contained three to four benzenic rings. Milatovic et al. (58F) analyzed bitumens from Iraq using IR spectroscopy. Their correlation may be used for the paraffin content determination in the bitumens. Kat0 et al. (43F) compared several structural analysis methods on pitches starting with IR. Structural modes of each sample were proposed on the basis of struct,ural parameters obtained by computer calculations. Rentrop ( 7 5 0 performed IR studies on bitumens from several countries. His results showed the proportions of C and H in each group. IR spectroscopy was used by Speight and Moschopedis (86F)to study quinone-type oxy en in petroleum asphaltenes and resins. Kaibara et al. ( 3 9 b have developed a rapid spectrophotometric method for determining asphaltenes in residual oils. Three papers usin X-ray techniques were published in 1979. Yen et al. ( 9 8 8 studied shale oil-derived asphaltenes combining the results from X-ray diffraction, NMR, and IR methods. Generally, shale oil as haltene consists of a heavily substituted linked or kata-congnsed system; the system is small, and the substituents have an average of two or three carbons. Schwager and Yen (78F)separated and characterized asphaltenes from five U S . coal liquefaction processes using X-ray scattering and ESR techniques. The X-ray studies suggested that about four condensed aromatic sheets were stacked on top of each other with ali hatic chains or naphthenic rings along the edges. The EgR studies indicated that charge transfer interactions were not significant binding forces between the molecules at room tem erature. Kim and Long (49F) characterized asphaltene coloids in heavy petroleum residua and liquified coals by X-ray scattering. Apparently the basic unit of the Job0 asphaltene colloids is a macromolecule rather than an aggregate.
MISCELLANEOUS COMPOSITION STUDIES Chemical Methods. A number of miscellaneous chemical separation studies were reported. Patwardhan ( 6 5 0 conducted a fractionation study using different organic liquids, e. ., chlorinated hydrocarbons, alcohols, ketones, etc. Good sefectivity was obtained only with hexane. In another article Patwardhan (66F) described a chemical separation method in which hexane in the amount of 5-20 times the sample weight was used to separate the asphaltenes. Extension of the method to industrial fractionation is discussed. Kam’yanov et al. ( 4 0 precipitated as haltenes with petroleum ether and they then were ozonized: A variety of techniques 98R
ANALYTICAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
including IR, UV, and NMR were used. The S atoms were located in the peripheral parts of the asphaltene molecules in the cross-linkages between separated fragments. The N atoms were concentrated in internal parts of the asphaltene molecules. Ramljak et al. (72F) developed a technique for separating free fatty acids from asphalts. A solvent-rec cling chromatographic column was used. Sergienko ( 8 3 4 presented an overview of the structure of petroleum resins and asphaltenes in various Russian crudes. Plyusnin et al. (68F) reported a study using titanium tetrachloride fractionation of petroleum asphaltene-resins dissolved in benzene. The number of Tic& molecules required to complex each asphaltene molecule varied from one to two in the first to 20 in the last fractions. The recipitate fractions differed little in composition and molec& weight was poor, perhaps because the complexed molecules precipitate immediately, before electron-accepting titanium chloride molecules can equilibrate over donor sites with different binding energies. Oelert and Neumann (64F) re orted a separation and characterization study of very hig! boiling and nonvolatile mineral oil products using an anion exchanger activated with NaOH. Their study reported on the roles of the various fractions in petroleum. Steffgen et al. (88F)developed a technique which gives reproducible results for the determination of asphaltenes in fuels from coal hydrogenation. Data are presented for this method in which a large excess of entane is added to a slurry prepared from toluene solubles angtoluene. Smith et al. (84F) studied asphaltenes and preasphaltenes se arated from H-coal vacuum bottoms. The results indicated &at pre-asphaltenes consisted of 30-35% of bases stronger than water but a substantial part of the nitrogen was in structures of lower basicity. Sulfur concentration was higher in the acidic components than in the basic or neutral. The pre-asphaltenes appeared to be poorer in aliphatic substituents than the asphaltenes. Vymetal and Kulhankova (95F)separated components of the quinaldine fraction from coal tar by treating with aqueous urea and crystallizing out the clathrate. Rustamov et al. (76F) developed a quantitative method of determining of calcium salts of aliphatic sulfuric acids of asphalt. The complexing with titanium tetrachloride to certain synthetic polymers modeling structural fragments of asphaltenes was reported by Khokhlova et al. (45F). The molar enthalpies of the quinaldine interaction with coal-derived asphaltenes and heavy oils were used to characterize coal-liquid fractions as discussed by Tewari et al. (9OF). Calorimetric, NMR, and elemental analysis data were obtained by Tewari and Li (91F) by h drogenating a Kentucky coal under different process con& tions. Long ( 5 3 0 stated that recent studies of asphaltenes showed that asphaltenes are composed mainly of polar aromatics with appreciable content of naphthene aromatics and traces of saturates. This information and solubility theory suggested a new definition of asphaltenes in terms of a plot of polarity vs. molecular wei ht. Speight and Moschopedis (86F) presented a critical c&cussion of structural and compositional studies of asphaltenes. The paper indicates the correct method for isolating asphaltene and also the limitations of spectroscopic, chemical, and X-ray methods of structural analysis. Yen (97F) discussed the structural differences between petroleum- and coal-derived asphaltenes. Thermogravimetric Methods. de Camargo and Neumann (20F) reported the results of compositional studies on bitumens using thermogravimetric, differential thermoanalytic, and pyrolytic gas chromatographic means. The DTA curves were characterized by continuously increasing vaporization and decomposition endothermal effects. The volatility of bitumens was determined by DTA and pyrolytic gas chromatography. Primak et al. ( 7 1 0 made a thermogravimetric study of the oxidative polycondensation of vacuum residues. The plateau on the resulting curves corresponded to the formation of cross-linked thermostable structures. Fluorescence and Photocolorimetric Methods. Jacob (38F) through the use of fluorescence techniques obtained information which affords positive identification of the type of bitumen in rock inclusions. Klink (51F) first separated hydrocarbon mixtures on a silica gel column using Color
PETROLEUM
Corrector 50, 1-butylpyrene, and Sudan 111. The saturated hydrocarbons were eluted first, then the olefins (yellow-green fluorescence), and then the aromatics (blue fluorescence). Brule and Druon (17F) studied the effect of blending temperature and rate of cooling on the morphology and physical roperties of bitumen binders. The morphology was examined Ey fluorescence microscopy. Tirak'yan et al. ( 9 2 0 developed a method for determining photocolorimetrically in benzene the composition of asphaltenes. They reported that analyses took about an hour and the precision was good. Baranova ( 3 0 proposed a qualitative and quantitative luminescence-bituminological analysis, finding it most suitable for testing carbonaceous substances in rocks. General principles and applications are discussed. Electron Microscope Methods. Donnet and Kennel (260 performed electron microscope studies on the morphology of two bitumens, representing the sol and gel types. The asphaltenes in the sol bitumen formed well-organized isolated agglomerates, whereas the asphaltenes of the second bitumen appeared as a continuous, unstructured network. Constantinides et al. (22F) found the structures of heptane-washed asphalts were easier to observe when the asphalt had low paraffin content, a high dispersion coefficient, and low molecular weight ratio of asphaltenes-resins. Kim and Long (48F)reported that they could characterize a heavy residuum by a small angle, X-ray scattering technique which showed that the unit detected was either a basic molecule that did not aggregate or that the aggregates did not break up in solution. Scanning electron microscopy was applied to the study of asphaltenes and their thermolysis products by Rebagay and Mori (740. The research indicated that temperatures higher than 110 "C may be required for the elimination of asphaltenes from coal liquids. Several tar sands studies were reported. Myers (62F) in a US. Patent has roposed a method to separate the bitumen from the tar sandy! agitation of the tar sands with a mixture of equal parts aqueous tannic acid and 29% aqueous NH40H. The bitumen recovery rate increased with temperature and the separation was completed at 90-90 O C . Anderson ( Z F ) , in another U.S. Patent, described a hydroseparation process for the aqueous extraction of bitumen from tar sands. Moschopedis et al. ( 6 0 described a flocculation technique for obtaining water-soluble aliphatic acids from Canadian Oil Sands. This first step was followed by extraction and methylation. They found it was possible to remove clay from sludge by flocculation. Bunger et al. (19F)performed composition and properties studies on both Utah and Athabasca tar sand bitumens. Thev found that the bitumens differed significantly. Molecular Weight Studies. Moschopedis et al. (59F)used vapor pressure osmometry to determine the molecular weights of asphaltenes. The data are interpreted in terms of association of the asphaltene units in solvents of low dielectric constants and dissociation in solvents of high dielectric constant. Data derived from viscometry methods yielded inconsistent results. Moschopedis et al. ( 6 0 0 performed a study using cryoscopic methods to determine the molecular weight of asphaltenes. The results showed pronounced variations in molecular weights dependent upon asphaltene concentration and solvent type. Speight and Moschopedis (85F) in a letter to the editor of Fuel noted that for any one method, the observed molecular weights indicated that the asphaltenes form molecular aggregates even in dilute solution, and this association is influenced by solvent polarity, asphaltene concentrations, and the temperature of the determination. Kiet et al. (46F)re orted on the effect of molecular weight and composition on t e glass transition temperature. Masek (55F)studied the mean molecular weight of petroleum asphaltenes by a light scattering technique. The concentration of colloidally dispersed components affected the behavior of heavy fractions during hydrocracking.
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ASPHALT RHEOLOGY Marvillet ( 5 4 0 studied the influence of asphalt composition on its rheological properties. From the analysis of the constituent hydrocarbon groups, the soft asphaltene phase shows Newtonian behavior, but the nonvolatile maltenes have a
complex behavior at low shear rates. The viscosity of coal liquids correlated with their asphaltene content, with the phenol content, and with the average molecular weight of the asphaltenes. The viscosity also depended strongly on the intermolecular association of acidic and basic subfractions, according to Bockrath and Schweighardt (SF). ASPHALT PAVING Kasahara (42F)studied the physical properties and deterioration characteristics on asphalts recovered after serving as pavements. Changes in physical properties and composition i b oven test and the rolling during deterioration by the thin f thin film oven test were also reported.
CATALYSTS 1. P. Debies, C. L. Kibby, J. E. Lester, and L. A. Pedersen Gulf Research & Development Co., Pittsburgh. Pennsylvania 15230
The impact of surface science instrumentation on catalyst characterization and research is best exemplified by the appearance of reviews such as Somorjai's (153G) on the relationship of catalysis and surface science and that of Delgass et al. on the use of modern spectroscopies in catalysis (40G). The list of acronyms continues to grow with low-energy electron diffraction (LEED),photoelectron spectroscopy ( W S or ESCA), ion scattering spectroscopy (ISS), and Au er electron spectrosco y (AES) appearing frequently in stu ies of catalysts. Cata&tic systems gettin the most attention continue to be the hydrotreating ca ysts containing predominantly Ni, Co, .Mot and/or W, Fischer-Tropsch catalysts, and the perennially mteresting supported noble metal catalysts including bimetallics. Because of the profusion of literature in this area, this review can only sample the advances in catalyst studies rather than give an exhaustive review. Elemental Analysis. Sykora and Dubsky (160G)determined the Pt content of re-forming catalysts by decom osing the catalyst at high pressure in a solution of HC1 a n 8 H 2 0 2 at 250 "C for >14 h and then precipitating Pt with 2mercaptobenzothiazole. To study the Pt-support interaction in mono- and bimetallic reforming catalysts, Putanov et al. (133G) treated the solids with acetylacetone for 6 h and determined a Pt-A1203 complex colorimetrically. Zakharov et al. determined Pt extracted from catalysts by amperometric titration of Pt(I1) using 10 mM Cr207- in 6-8 M H2S04 as the titrant and a rotating Pt electrode operated at +0.4 V vs. SCE. Ir(II1) and Fe(I1) are the only group 8 metals which interfere (180G). A technique employing spark-source mass spectroscopy was used to determine Pt (0.37%)and impurities such as Ti, Si, P, Cr, Mn, Na, and Mg (1ppm to 0.05%) in Pt/y-alumina catalysts. The results agree with those found by atomic absorption spectrometry (AAS), X-ray fluorescence (XRF), or spectrophotometry (127G). Bahr and Jedras reported that 0.1 to 1.0%Re in catalysts with or without Pt could be determined by forming a stable complex of Rerv and thoria which has t, at 390 nm in 4-6 N HC1 in the presence of excess SnC12 (78). In the presence of Pt, absorbance was measured at 440 nm to avoid interference. AAS was used by Sychra et al. (159G)to determine Re in re-forming catalysts. The effect of HC1, Al, and Pt in the AAS determination with a N20-C2Hzflame were discussed. Toei et al. (163G) have reported the use of 5-diethylamino-2-nitrophenol as complexing reagent in acidic aqueous solution or CHCl for colorimetric determination of Pd in catalysts. In the choroform solution, most common elements do not interfere at lo%. Ste s in the procedure involve pretreatment to remove asp altenes, acid/base extraction, MezSO partition, Fluorisil column cleanup, LC on an acetylated cellulose column and detection of the BaP by GC, HPLC with UV detection, and fluorescence analysis. Carbon-14 tracer techniques were used to document recoveries. Raverdino and Sassetti (127L) used a combination of GC and MS to identify the positional and geometrical isomers from Ca to C13 n-alkene mixtures from the “Olex” process. Both capillary GC and GC-MS methods were developed for analyzing structures with and without prior separation of the mixture into cis-, trans-, and a-isomer fractions on a column of alumina treated with AgN03. St. st. capillary columns (100 m X 0.25 mm) coated with DC-550 were used with a FID. Some portions of the isomer fractims were chlorinated before GC analysis for further confirmation. Direct GC without derivative formation is recommended for detng. @ isomers and direct IR for a and gcometric isomers. About 80% of the components of the mixturz can be identified by GC after chlorination of the alkenes and 95% by GC of the derivatives of the products of oxidn. with Os04. Montheard et al. (103L)determined acetylenes (alk-1-pes) in acetic acid medium by treating the solution with ethanolic AgNO in excess. Thesppt. formed is removed and titrated with dH4SCN with Fe as indicator until a stable red color is produced. The following compds. were detnd: hex-1-yne, hept-1-yne, oct-1-yne, non-1-yne, and ethynylbenzene. Several papers dealt with the use of HPLC for detection and detn. of specific compds. Johnson et al. (74L) reports on the sepn. of several fluorenes substituted with mainly Ncontaining grou s at two or three different positions. Normaland reversed-$ase HPLC was used on columns of Partisil 10 with detection a t 254 nm. Column and elution conditions
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PETROLEUM
are detailed, and relevant capacity ratios are provided for each separation. Murakami (107L)determined the retention behavior of 14 benzene derivatives using microscale HPLC on PTFE columns (80 m X 0.5 mm) packed with LiChrosorb RP-18, RP-8, Nucleosil C18, and Permaphase ODS at 30 atm. The benzene HCs were dissolved in methanol and 0.1 pL (50 pg of solute) applied to the column. Samples were eluted with water mixtures (30-90%) of methanol, ethanol, 2-propanol, dioxane, or acetonitrile at rates of 4 pL min-' and compds. detected by UV. The effect of varying eluent composition and column packing on capacity factor was studied. It was observed that a relationship existed between lo capacity factor and log molarity of organic solvent in the efuant. Dimitrova (32L) used HPLC to separate cis-trans isomers of unsaturated HCs using a A NO3-impregnatedsilica gel (10 pm). A 40 cm X 0.3-0.4 cm i.d column of Li Chrosorb Si 100 with a 10% loading of A NO give complete resolution of afkenes. The mobile phase was cis-trans isomers of C to a 0.5% solution of MkK idkeptane. Some isomers of alkadienes and trienes were also separated. Specific Compounds-Metals/Laboratory Methods. Koizumi et al. (84L)used a combination of techniques, HPLC, high-temp. furnace, and a Zeeman AA spectrometer for anal zing organometallic compds. The method was applied to T 6 L in NBS petroleum stds. with a recovery of 97.6% bein obtained at a 190-ng level and eliminated interference in P i and Cd detns. in the presence of the chlorides of Mg, Cu, and Ca. The general technique is to take fractions obtained by HPLC and decompose them in a special furnace using a tantalum sample cup. The atomized metal and vapors are swept into the spectrophotometer by a stream of Ar. Windsor and Denton ( I 71L) used an inductively coupled plasma detector for the elemental analysis of GC effluents and compared the response to other type detectors. In general, detection'limits, linear dynamic range and selectivity were comparable to FPD, argon, and low-pressure He microwaveexcited plasma detectors. The detector was used for detng. tetramethyltin in a mixture containing benzene, toluene, and p-xylene. Bertrand et al. (16L) discussed the detn. of Pb in lube oils down to 5 ng of Pb with an accuracy of *6%. The Pb is present as Pb naphthenate enriched in various natural isotopes of Pb. The sample is di ested in acid. Pb from the resulting aq. soln. is electroplatefonto a Pt anode, and the Pb on the anode surface determined by means of second ion MS using an ion microprobe mass analyzer. This p r o x e s data on the relative amount of each mass number component in the sample. Quantitation is obtained by adding to the sample a known amount of a std. Pb compd. with an isotopic composition different from that of the sample. Type Compounds-Laboratory GC Methods. Sojak et al. (14.55) used GC studies on the retention characteristics of various unsaturated HCs to determine the effect of slight structural differences. Data obtained from five classes of unsaturated aliphatic and substituted aromatics and other compds. containing 0 and C1 led to the conclusion that retention anomalies are associated with molecular structures on which the possibility of a ring conformation exists between a propyl group and the *-electron system of the remainder of the molecule. The propyl grou anomaly is evident from a lower retention index, a low PO arity, and a lower b.p. Johansen (76L) reports on an improved GC analysis of a-olefins. He used an all-glass system including columns coated with OS 138 rather than st. st. columns to obtain improved separation. Still better separation of a-olefins was obtained with glass open-tubular columns coated with nitroterephthalic acid-modified Carbowax 20M stationary phase. Polynuclear aromatics (PNA) separations were reviewed by Zielinski and Janini (174L). While it is impossible to cover all oints of a review article, it should be pointed out that these aut\ors felt that improved separation of PNAs usin nematic liquid crystal as the stationary phase is possible.. owever, some precautions must be observed to provide good results. Schulz (138L)describes the development of GC methods for improved sepn. of gasoline components, particularly asolines contg. olefins where capillary columns and precoumns for the reaction of reversible or irreversible sepn. of groups are used. Olefins and aromatics are absorbed b omplexation with AgN03 on Sterchamol while satd. H d are
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ANALYTICAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
unimpeded and thermally desorbed later for capillary sepn. Small branched olefins require the lowest adsor tion temp., while long Le., C5 olefins are completely adsorbed at -75 chain n-alkenes are most strongly bound, with 1-octene, for example, requiring 200 "C or more for desorption. Olefin recoveries, except terminal olefins having branched vinyl C atoms which undergo double bond displacement, are close to 100%. Other work on olefin separations was reported by Lukac and Nguyen (94L)where the C5 and c6 unsaturated compds. were separated from their parent satd. compds. A stationary phase of phenyl glycidyl ether was used and the retention indices of the C5olefins and two of the dienes were calculated. Sandra et al. (135L)shows the versatility of glass ca illary columns in which the stationary phases were polyox et!ylene glycols with mol. wt. ranging from 1 X lo5to 5 X 10 Normal sepns. are obtained with the more common classes of organic compds. with little tailing. Sepns. are made with high efficiency and over a wide temp. range of 50-300 "C. The columns have been used to separate various compds. in the classes of alkanes, amines, fatty acid methyl esters, organochlorine insecticides, and other type compds. Poznyak et al. (121L)used a flow-through UV detector for detecting olefins eminating from GC columns. The method depended on the measurement of excess O3 at 254 nm after reaction with the olefin. Reliable detection depends on maximum conversion of olefins to ozonides. Conditions which gave good results were: sample volume, 3 pL; reaction cell length, 2.5 cm; flow rate of O& mixture (25 pM O&, 1.5 mL min-'; and carrier flow rate, 1.5 mL min-'. Dahlmann et al. (3015)determined retention indices for a series of compds. in five classes of compds. including: + m e a , alkenes, aromatics, alcohols, and esters. Three different columns (2 m X 2.7 mm) were used: (1)1.5% Apiezon L on Chromosorb G AW-DMCS (80-100 mesh); (2) 5% OV-25 on Gas Chrom Q (100-120 mesh); (3) 5% of Silar 5 CP on Gas Chrm Q (100-120 mesh). Columns were temp. programmed from 25 to 250 "C at 10 OC min-' with Nz as carrier, and detection was by FID. Correlation between several physical properties such as b.p., mol. wt., density, and retention indices were made. Use of the best combinations permitted calculations close to observed retention indices. Carson et al. (26L) determined the GC relative molar response (RMR) of C5-C8paraffins on a 10 ft. X 0.25 in. column acked with 10% Carbowax 20M on 60 80 mesh Chromosorb at 125 "C with a TC detector. Two b ends, each containin 68 components were added to benzene which was also use! as the standard. The data showed that within the aliphatic and cyclic HCs there exists a fixed RMR unit difference of about 16 RMR units in a homologous series. It is to be expected that a similar unit difference in RMR will be found for other homologous series. Type Compounds-Other Laboratory Methods. Several publications reported on the use of HPLC methods for the sepn. of com ound types. Ageev et al. (4L) used columns of hydroxylatecfsilica gel to separate monoalkf and plymethyl derivatives of benzene with hexane as t e mo ile phase. Retention results were studied as a function of mol. structure and the free energy of adsorption. Retention times increased with the no. of methyl groups and they decreased with the length of the alkyl chains. Selucky et al. (140L)used HPLC as a means to fingerprint crudes and etroleum products. The system used silica gel packing ancfheptane as eluant with UV and RI as detectors to determine HC com d. classes in crudes, their relative distributions, and the !.p. distribution of the saturates in 10-12 min. Heavy crudes took about 18 min. to complete. A combination of GC and HPLC on mixtures of aromatics indicate that mono- and diaromatics and often di- and triaromatics can be differentiated from alk 1 and cyclo alkylaromatics, The combination of GC and PLC wag used to fingerprint samples of automotive and aviation gasohm, lube oils, and other refinery stream products. Parris (I17L) used IR to detect LC eluants in separating saturated triglycerides, . k e a ((26 thro h c ), and 5 alkenes a st. st. column (Clothrough C1J. Studes were performa (25 cm X 4.6 mm) packed with Zorbax ODS with a DuPont IR detector and a 254-nm fixed-wavelength photometer. Mobile phases used were mixtures of acetonitrile, tetrahydrofuran, and CHZCl2.The system's sensitivity with glycerol
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PETROLEUM
tributyrate was -200 ng. Good separations are obtained by matching the IR absorbance of the initial and final mobile phase solvents. Colin and Guiochon (28L) performed reversed-phase LC to determine selectivity for homologous series of n-alkanes, n-alkylbenzenes, and n-methyl esters. Columns were packed with LiChrosorb R P 8, R P 18, pyrocarbon (Spherosil XOB), and Partisil ODs. Column peak capacity was found to be pro ortional to the resolution. Separations obtained mainly wit{ branched chained alcohol series indicate that carbon adsorbants are more selective than chemically bonded phases. The correlations may be useful for predicting retention sequence. Antipenko et al. (IOL)by selective bromination of porphyrins with HBr indicate the method’s use for direct determination of the open positions in por hyrins. By MS analysis of the brominated products of vana&lporphyrin (VP), concentrates from two crudes showed that 57-70% of the porphyrins contained one to three bromine atoms, which corresponds to nonsubstituted P-position in the pyrrolic rings of the original VPs. Compounds with zero, one, or two open positions in pyrrolic rings formed continuous homologous series. Schmitter et al. (137L) analyzed for carboxylic acids in crudes by a combination of techniques including GC, LC, electron impact MS, and chemical ionization MS. The acids were extracted from the crude on a column of KOH treated silica gel and then converted to their methyl esters and purified on a similar column followed by thin-layer chromatography and urea-adduct methods. Fractions were obtained containing straight chain, branched chain, and cyclic esters. The straight chain esters were further separated by GC on a column (18 m X 0.5 mm) coated with OV-101 and temp. programmed (4 “C min-’) from 100 to 300 “C. The other fractions were separated and identified by GC-MS methods. Grushova et al. (57L) used the relative chromatographic polarity parameter (P)as a tool for the rapid evaluation of the extraction characteristics of binary solvent mixtures. Ethylene glycols or sulfolane were mixed in varyin proportions with N-methylcaprolactam, N-methylpyrrolifone, methylcellosolve cyanoethylate, or tetrahydrofurfuryl cyanoethylate and then used as the stationary phases in GC separation of a std. 1:l benzeneln-hexane mix a t 30 “C. The calculated P valves were correlated with extraction selectivity coef. (p) and the distribution coef. ( K )of the solvent mixtures measured in direct extraction experiments. As P increased for the solvents, p increased linearly while K decreased. High extraction efficiencies were observed when P > 80% while when P was between 70 and 80%, the combination of selectivity and solvent power was maximized. Gallegos (43L)analyzed organic mixtures by metastable ion methods using a double-focusing MS. Metastable transition s ectra can be used in two ways by MS; one uses a single ion gtection while the second uses mass ratio and intensity information. The latter approach was used to analyze alkane, alkene, and cycloalkane isomers as well as HC mixtures.
k
PHYSICAL PROPERTIES Laboratory. Stuckey (15115)used two different approaches to obtain wt. response factors of GC detectors for GC “simulated” distn. (GCD) of crudes (TCD) and refined pet $ nature of $the troleum streamsT(FID), basedEon the chemical samples. Am empirical approach was used with crudes and a statistical approach was applied to the refined petroleum streams. Results showed that a common response factor should not be applied; response factors are needed for each data point or temp. An equation was developed which relates the response factor to the UOP characterization factor and the b.pt. GCD data can be converted to wt. % and/or vol. % by using response factors. GCD can be used as a quality control method and as an inexpensive crude assay tool and provides a rapid method of defining product distribution on a very small sam le. da Silva et al. 6 I L ) described the use of GC to determine the solubility of gases in liquids a t ressures from 760 mm to 10-20 mm. The gas is equilibrate! with the solvent at the desired temp. and pressure for 24 h in a cell consisting of two connecting vessels with a volume ratio of 5:1000, and a GC analysis of the liquid is then carried out. Method precision is 3%. The solubility of 0 2 and NO in n-hexane, acetonitrile,
and other solvents showed good agreement with lit. values. In the first of two papers, van Kasteren and Zeldenrust (159L)discussed the design and evaluation of a flow colorimeter which can measure enthalpy-temp. relationships for small amounts of condensable gase at 100-300 K and up to 70 bars with an accuracy of about 1% . This device can also handle two-phase gas/liquid systems and operates a t a constant pressure over the entire temp. range independently of the vapor pressure of the gas mixt. Performance was tested on pure CH4 under supercritical and critical conditions. In the second paper, van Kasteren and Zeldenrust (160L)compiled exptl. results by using their flow colorimeter and compared these with predictions based on a modified RedlichKwong (MRK) equation of state. The heat capacities and enthalpies of the pure forms of the ma’or components u s u d occurring in natural gas (CH4,CzH6,C3k8,N2)were measured: These exptl. data were used to improve the predictions of an MRK-based computer program. Cooling curves of binary mixts.of these components and of two multicomponent mixts. of Nz with C1-C5 and C1-C3 alkanes a t 110-270 K were then determined with the computer program. The predicted data were in fair agreement with exptl. except for the liquid-phase heat capacities of the CzHs/Nzand C3H*/N2 binaries, which were much lower than exptl., roably because of a liquid-liquid phase sepn. at low temps. #mall amounts of He (0.3%) increased the liquid-phase heat capacity of a multicomponent mixt. but not that of pure CH., or Nz. Karaiskakis et al. (77L) used GC to determine the enthalpy and entropy of adsorption of pentane, hexane, heptane, cyclo ntane, cyclohexane, and cycloheptane on Al 0 modified witr4-20% of an alkali halide (five chlorides a n d d a F , NaBr, and NaI). The entropy and enthalpy varied widely. Two new parameters calculated in and terms of the thermodynamic compensation effect, L, provided a better characterization of adsorption t an enthalpy and entropy. The only necessary condition for a compensation effect to occur is that the mean values of he coordinates for the various intersection points of the relevant straight line lies within a small range. Disking et al. (33L) developed criteria for evaluating the thermal oxidative stability of oils using chromatography, differential thermal analysis, and differential thermo avimetric analysis. Unfortunately, only the title of this articg was translated for the abstract used as B basis for this review. Process Analyzers. Many of the following physical property analyzers have been discussed in previous reviews and will be mentioned briefly here to update applications and improve instrumentation. In one article (124L),the Totco purity analyzer is discussed. This analyzer determines purity based on freezing point determinations for liquids freezin between -40 and 100 “C. The analysis cycle of 12-18 min s t d permits continuous open or closed-loop monitoring of processes and has been used in US., Europe, and Japan. Common chemicals which are monitored are p-xylene, styrene, benzene, p-dichlorobenzene, phenol, and acetic acid. Another device designed to continuously monitor jet fuel freeze points is the Totco freeze point analyzer. The unit operates over the range of -65 to -15 “C and is used on distillation columns or blenders to keep the product within specification. The Home Instruments’ Distillar on-line analyzer (125L) carries out a standard distillation test in 20 min and follows the ASTM D-86 test closely. It w i l l record on a re a chosen ? distillation! point normally S tested by A methods. The basic components of the analyzer are: flask, heater, condenser, calibrated receiver of st. st., temperatures sensing element, a 100-mL charge burette, and electrical and pneumatic components for automatic operation including filling, flushing, and drainin The analyzer is air purged. Six models are available depensing on requirements of the user. Walko (16.55) discusses a new gas and liquid densitometer of the insertion type useful on process fluids, slurries, and LNG. The vibration-element sensor is enclosed in a “Minitube” and the coils are arranged outside the tube and enclosed. Floating faces on the transducer act as axial loading plates and compensate for the liquid pressure inside the tube. The system can be used a t cryrogenic or high temp., but pH should be above 5 in pipelines and tanks. Prototypes were accurate to within 0.1% in LNG tests. Other uses are to detect oil-water interfaces and determine oil-water ratios. Solartron also makes a version that when calibrated with Argon w i l l give ethylene density to within 0.2 % .
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Williams (170~5) also discusses a density analyzer, but the principle is based on the adsorption of high-energy y-rays. The same unit can be used for level measurement as well as the density of liquids or the amount of solids in slurries. The Paper provides tips on nuclear gauging including: safety, icensing, source decay, and factors affecting density gauging, such as: stratification, air bubbles, vibration, corrosion, and temp. These and other factors to be considered in applying the technique to slurries, sewage sludge, interface detection, and level auging are also discussed. Morris &04L) has collected comments from manufacturers of prolems encountered with sensing interface levels and provides possibilities for improved measurement. whether CLP Emulsion layers usually provide problems for most interface levels, as do interfaces with motion. Several other aspects of sensing interface levels are discussed too numerous to mention here.
IMPROVED INSTRUMENTS AND TECHNIQUES Laboratory-GC Methods. About half of all references in this section deal with some aspect of gas chromatography. Soroka (147L) used a statistical techni ue known as target factor analysis (TFA) to study the fo(howing: gas-liquid chromatography data matrix involving 49 solvents (alkanes, alkenes, alkyl halides, monomeric solvents); 6 matrices from McReynolds' compilation (ketones, aldehydes, carbonyls, and mixed functions1 grou 9); gas-solid chromatographic data involving retention in&xes (alkyl and aromatic solutes and ionic forms of Amberlite A 15 and Chromosorb P); and the analysis of an ion exchan e problem. A com uter program (FACTANAL)facilitates appfication of TFA to tiese problems Hirsch et al. (68L)used correspondence factor analysis (CFA) to identify the major influences on the behavior of satd. and unsatd. HCs in gas-solid chromatography on ion exchangers in different cationic forms, using stationary phases prepared from sulfonated Porapak Q ethylvinylbenzene/divinylbenzene copolymer. CFA shows that ion exchangers in the Ag', Nil+, Zn2+,and Cd2+forms have different selectivities for unsatd. HCs. Steric hindrance of this selectivity occurs with the larger cations, such as Ag+. The H', K', Na+, and T1+ forms are practically nonselective relative to the unsulfonated copolymer matrix. Gangwal et al. (46L)discussed the reliability and limitations of pulse chromatography in evaluatin properties of flow systems. They used theor. analysis an8 adsorption experiments with pulses of CHI and C2HG on silica gel to evaluate the technique for determining the axial dispersion coefficient, adsorption equil. constant, chemisorption rate constant, mass transfer coefficients, effective and surface diffusivity, reaction rate constants and the Kubin-Kucera adsorption model. Experimental reproducibility was good. The validity of the model was confirmed by the agreement between experimental and predicted effects of velocity, particle size, temp., and bed length on model parameters. Results on pore diffusivity and adsorption equil. constant were in good agreement with literature values obtained by other techniques. Pulse chromatography was unsuitable for determining the rate constant of physisorption and the mass transfer coefficient. A total of 50 references are given. Norris (113L)discussed the applications of analytical chromatography in petroleum technology and lubrication. The first of two papers cover history, theory, columns, and packings for adsorption, partition, and exclusion systems, prepn. of samples, control of conditions, and the hydrocarbon skeletons of interest in petroleum chemistry. Also discussed were PC and TLC and their applications in the analysis of additives in lube oils and greases. In the second paper, Norris (114L) continues his discussion, covering the behavior of H2 in GC columns, sepn. of wide-boiling range samples, programmed temp. GC, the capillary column, and automatic GC analysis. Also discussed is the application of GC to use! engine oil anal., detg. oil vis., gasoline analysis, and identification of ur.knowns from a library of reference spectra. The article also dlscusses the development of high-performance of LC, reversed hase chromatography, and size-exclusion chromatography. & l e ~of applications of LC to motor oils and gasolines are given. Laurgeau and Barras (88L) showed that two samples in'ected simultaneously into a GC column is pseudorandom Binary sequence from different sampling devices yield output 124R
ANALYTICAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
data that can be analyzed by decorrelation techniques into separate chromato rams. The basic theory and exptl. programs are discusse! and illustrated by sepns. of the components of propane-butane mixts. A number of papers appeared on GC columns and column techniques. Rooney (131L)discussed the advantages of glass capillary columns in the analysis of petroleum products on a 60-m column coated with SP-2100 with flame ionization detection. Hz, He, and N2 carrier gases were compared. The lower vis. of H resulted in shorter analysis times. Brander (19L)describe8 a new glass capillary system for the Varian Model 3700 GC. The use of glass inserts in the capillary injector permits direct, split, and splitless modes of operation without removal of the capillary column. Branching of the column is facilitated by using ferrules. Good retention time repeatability is obtained because of the thermostated pneumatic system and precise column oven tem . control. The system was tested on a mixt. of Cllto CS H&. Anderson et al. (8L) described a novel dual glass-capillary system. The two columns, each in its own oven, are connected by a heated transfer l i e , permitting the use of optimum stationary phase polarity, thus improving selectivity. The use of flow circuits allows changes in the direction of the column effluent. The transfer line can serve as an intermediate trap. The design and modification of the system are described and operatin parameters are discussed. Chromatograms of standarf arylalkane mix$. are given to illustrate possible sepns. Evrard et al. (37L)described a sampling system using heated sample phials and a packed precolumn for high-temp. isothermal capillary GC. The sample is diluted with 0.1 or 0.2 mL of volatile solvent placed in the phial and the phial placed in a loading chamber. N2 is used to purge the system, the phial is heated, and the vapors are condensed on a precolumn packed with OV-1 (1-12%) on Gas-Chrom Q (80-100 mesh) and operated in the back-flush mode. The substances to be analyzed are then transferred via a wall-coated capillary trap to a capillary column for analysis. The device is controlled by a programmable electromechanical processor. Mixts. of n-alkanes (C14-CM)have been analyzed with a precolumn (at 100 "C) contg. 12% OV-1 and a 25-m analytical column (at 242 "C) wall-coated with OV-101. Blanks are free of ghost peaks when thermally prestripped phials are used. Sharp (143L)presented a practical guide to the use of wall-coated open-tubular glass capillary columns in lab GC which should facilitate setup and operation of such columns by ersons unfamiliar with their use. Sample introduction anfdetection (FID) are discussed, and the prepn. and installation of com. lass capillaries are described in detail. Applications descri%edbriefly include the analysis of petroleum fractions. Grob et al. (55L) discussed the principles and basic techni ue of deactivating glass capillary columns by silylation. T%e glass is leached with HC1 and pure si1 latin agent (hexamethyldisilamne or tetramethyldiphenyldisiLe7 drawn into the column to about 7% of its total length and flushed through the column with carrier gas. When the liquid has been displaced, the column is evacuated, sealed, heated slowly to 400 OC, and held at this temp. for about 3 h. The column is then cooled and flushed successively with CBHBCH3, CH30H, and E g o . The column may then be coated with an appropriate stationary phase. Factors influencing column performance are discussed. The sepn. of test mixts. of HCs, carboxylic acids, and drugs is illustrated. Badings et al. (13L) described the prepn. of wall-coated open-tubular capillary columns after surface roughening using amorphous silica. The capillary is leached and treated with a plug of dil. sodium silicate soln. to deposit a small amount of amorphous silica even1 on the inner surface, and finally b a stream of HC1 gas. detailed procedure is given for stab&ing deactivating, and finally coating the roughened surface. Performance data are iven for several columns so prepared, including sepns. of afkanes on Carbowax 20M. Toth (157L) compared the sepn. efficiency of packed steel or glass capillary GC columns having roughened or smooth internal surfaces with different stationary phases at 50 and 100 "C for various paraffinic and aromatic HC mixtures. Important parameters are peak resolution per unit lenkth, effective number of plates per unit length, rate of formatlons of effective plate number, type of column, the stationary phase, and the partition ratio. A total of 19 references are given. Orav et al. (116L)studied the GC sepn. of Clo to Clz alkene
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PETROLEUM
cis-trans isomers at 60 to 80 "C on st. st. capillary columns (0.25 mm x 100 m) coated with 1,2,3-tris(2-cyanoethoxy)propane. The retention indexes and their temp. increments and structural increments were correlated with the structure of the isomers. Results were compared with those obtained on columns coated with less polar stationary phases. Galli et al. (45L) described an efficiently cooled on-column injector which isolates the end of the column from the oven temperature, eliminating "discrimination" of compounds in a given sample. Coolin is achieved by a stream of air entering the area of the capi lary fitting and flowing alon the outside of the capillary into the oven. Problems cause by insufficient cooling are discussed, and the efficiency of the s stem is illustrated by using test mixtures of alkanes (C18-8a). No band broadening occurs because of the cold spot at the column inlet. Lafosse and Durand (87L) studied squalane, 1,3,5-tricyanopentane and mixts. of these two compds. as stationary phases on Gas-Chrom Q (80-100 mesh) in st. st. columns (0.125 in. outside diam.) for GC separation of compds. having widely different polarity such as HCs, alcohols, haloalkanes, nitroalkanes, heterocyclics, etc. The mixed supports were prepared by either by coating the support with a mixed soln. of the two phases or by mixing supports coated with the single phase. The two methods of preparing mixed phases gave equivalent results. Separation was carried out a t 60 "C with N as a carrier gas and FID. Retention vols. are tabulated and conclusions drawn about the interaction of the solutes with the nitrile groups as an aid in selecting stationary phases for GC. Nawrocki et al. (111L)studied the sepn. properties of poly[Cu(II) di-n-hexylphosphinate] as a GC column packing for homologous series, isomers, and compds. with close b.ps. The sepn. of impurities in a-methylstyrene was used as an example of contamination analysis. Pscheidl et al. (126L)discussed elimination of the effects of the solid sup ort (Porolith) on the GC stationary solvent phase. A Cu capiary tube was used without a solid support, and the support was treated in various ways to eliminate its effect. The stationary liquid hase used was 1,l-diphenylethane, and the sepn. was Carrie out using cyclohexane, cyclohexene, and CsH6. The analysis is related to the hydrogenation of cyclohexene. Blyuss et al. (17L) showed that the se n. efficiency of GC systems with parallel multiple columns is getter than for those systems using sequential operation of columns. Examples are iven with Polysorb and mol. sieve columns for the sepn. of f I 2 , 0 2 , N2, CH?, C02, and C2H6. Pretorius et al. (122L) discussed optimization of GC resolution of multicomponent mixts, using temp. variation of series-coupled columns. One column was packed with Chromosorb coated with 4% of OV-101, the other with Chromosorb coated with 4% of Silar 5. Each column was placed in a separate oven, and the columns were connected in series, N2 carrier gas was used with FID. A mixture of acetophenone, benzyl alcohol, and dodecane was used. The temp. of the OV-101 column was held a t 80 "C and the temp. of the other column was varied. The relative retention values of the solutes can be dramatically changed and elution order can be reversed. Zhukhovitskii et al. (173L) described the technique of "limiting chromadistillation". In this technique, before sepn. is carried out, the GC column is wetted with a component of volatility significantly greater than that of the sam le components. The technique is illustrated by data on tRe sepn. of a mixt. of C6 to C9 alkanes, using a column (100 cm X 0.3 cm) filled with glass spheres (0.7 mm) and operated a t 21 "C with He as a carrier (flow rate at column exit = 18 mL/min). Matsuoka et al. (97L)described the use of short precolumns contg. hydrogenation catalysts in a GC between the injector and a squalane-coated capillary column using H as a carrier gas. A com lete hydrogenation catalyst was used to establish the skeletafstructures of C to C8 HCs, and an intermediate catalyst was used to cause double-bond migration in unsatd. compds. This technique ermitted detn. of retention times of several unsatd. compg. with the use of only a few std. samples. Variation in the precolumn temp. gave the thermodynamically predicted changes in the ratio of hydrogenated and nonhydrogenated products. Thus 0.5% Pd on A1203a t 180 "C gave complete hydrogenation, and at 270 "C and above six-membered rings were increasingly dehydrogenated to yield the corresponding aromatic compds., but aliphatic corn ds. remained in the reduced form. A 250-mg sample of P l o n
f
d
B
Chromosorb at 100 OC gave complete reduction of very small samples (0.02 HL)with no side reactions; 10 mg of catalyst gave partial hydrogenation and double bond migration (1pL sample). Gaspar et al. (47L) described a computer-controlled automatic GC which used a fluid logic gate as the sampling device for introducing the sample as a narrow band a few ms wide. Difficult sepns. (e.g., a light asoline) can be made in a few seconds using short open-tub& columns (< 1m) with narrow i.d. (< 100 km). Ferguson and Luke (39L) gave a critical appraisal of the FPD in petroleum analysis. Experience was summarized under the headin s inequality of response, quenching of S response and lac of sensitivity and under three topics: analysis of individual S compds. in the 15" to 65 "C cut of crude oils, the S fingerprint of crude oils, the evaluation of a dual-flame detector. Wenzel(167L) summarized questions and answers (discussed at ACS short courses) concerning the Melpar FPD GC detector. These include causes for a decrease in sensitivity for S, deterioration of the photomultiplier tube as a cause of loss of sensitivity with time, prevention of FPD solvent flame-out, and prevention of S chemiluminescence quenching by eluting HCs. Stockwell (149L) described automatic analysis by using hybrid chromatographic systems to provide unique identification of certain components. Such systems include GC-colorimetry, N-selective detectors, chemiluminescence detectors linked to specific catalytic reactors, and vidicon or lineardiodearray spectrometers used with LC. Applications include detn. of components of gas oil. Phillips and Goldan (119L) discussed the enhancement of electron capture detector (ECD) sensitivity to nonelectron-attaching compds. by addn. of N2O to the carrier gas. In the GC se n. of H2, COz, and CHI on Porapak Q and Mol Sieve 5Ae!t addn. of N20 to the N2 carrier gas produced a large increase in the sensitivity of the ECD to these compds. with no detectable change in peak width, eak shape, or retention time. This enhanced response is attriEuted to the reaction of these compds. with 0- to form stable negative ions, which interrupts the normal steady-state reaction sequence. At a signal to noise ratio of 2, the minimum molecules. detectable limits of these compds. is about 1X The as-yet-unpublished detn. of pg quantities of C2H,through C6H14 and other org. compds. is noted. Schwarz et al. (139L) described on oscillating slit mechanism for detg. H isoto ratios in a microwave induced plasma. HCs (nondeuteraterperdeuterated, or partially deuterated) emerging from a GC (using He carrier gas) were subjected to a low-pressure microwave discharge, which fragmented the compds. and generated intense atomic emissions. These signals were led to a monochromator provided with an oscillating exit slit so that the H and 2H signals passed alternately to the photomultiplier, the output of which was resolved by two lock-in amplifiers. The ratio of the two signals and H/2H in the mixts. was rectilinear over more than 1 order of magnitude. The method was also applied to isoto e diln. analysis, where perdeuterated naphthalene was adfed to a water sample cont traces of naphthalene and benzene and the HCs were e x t t into an org. solvent for analysis. Henneberg et al. (65L) described an open-split interface for high-performance GC-MS which has a glass restriction and is provided with a flow of scaven er gas. With a small scavenger flow, dead-volume tailing of%rge peaks is avoided; with a large flow, peaks that would otherwise be too large are diluted. The system was tested for alkanes and various polar mixts. and was found to have no effect on the quality of the chromatogram. At higher temps., adsorption was a limitin factor. Pt capillaries were inferior to glass. D'Orazio (34157 used a Raman multichannel spectrometer as a detector for a GC using a column (0.25 mm X 15 m) coated with OV-101. The GC effluent was passed through the focus of an Ar+ laser beam in a Raman spectrometer system and the beam was directed to the entrance slit of a single grating monochromator and via an objective to a 500-channel array detector. Conditions for detg. benzene were established and the detection limit for toluene in acetone was detd. The sepn. efficiency for fractions of cyclohexane and benzene was measured, and 0-and m-xylene in a mixt. with toluene, benzene, and acetone, were readily identified. Ecknig and Polster (355) studied the elution of n- and isoalkanes from mol. sieve 5A with supercritical C02 as a
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mobile phase, in the ranges from 0.5 to 20 MPa and from room temp. to 200 "C. n-Alkanes up to Cl4 can be sepd. individually and those up to Cm as a group from isoalkanes by appropriate selection of temp. and pressure. Several pa ers dealt with sam le introduction into the GC. Kennard ancfLaskowski (80L) Bescribed the use of a hot air to heat samples in a Hewlett-Packard 7671 A autosampler. g e gun is fitted to the sampler tray to heat samples awaiting injection. This permits injection of waxy or viscous samples with the instrument in the automatic mode. The s stem incorporates a device to prevent overheating. Grog and Heukom (56L) discussed the influence of the syringe needle on the precision and accuracy of vaporizing GC injections, usin a C9-C4 alkane test mixt. and stream splitting on a capiflary column. The discrimination of the high boiling components in the injector is mainly due to a selective elution of the sample out of the syringe needle. Different methods of handling the syringe needle were tested, and the discrimination is uantitated and correlated with the material left in the neehe. The Sam le should be pulled back into the barrel of the syringe a n f t h e needle allowed to warm up in the injector before the sample is transferred into it. Solvent flush may be preferred for com onents sensitive to the hot metal surface of the needle. fonchik and Walker (146L) described an inlet (for capillary GC for trace analyses) consisting of an 11.4 cm long glass-lined st. st. tube for direct injection of the sample without purging on venting into a Varian 3700 GC. n-Hexane (99% pure) analyzed on a Squalane support-coated o en tubular (SCOT) column gave Analysis of a C -c13 mixt. of a 1 ppm cyclopentane pea!. n-alkanes on an OV-l7/SCOT column with the Jirect in'ection inlet and with a com. available splitter inlet showed little difference in column efficiency between the two inlets. The direct inlet is also useful for wide-boiling range mixts. and thermally labile compds. since a high injection port temp. is not required. A c,-c16 n-alkane mixt. was sepd. with an in'ection port temp. of 150-250 "C, compared with the 300 "dinlet temp. required with a splitter inlet. Tejedor (154L) also described direct injection into capillary columns for trace analysis using identification by MS. No resolution loss or excessive loss of peak symmetry was observed, and the method can be used routinely without column deterioration or efficiency loss. The method was studied by using a st. st. column (0.25 mm X 50 m) wit UCON 50 HB2000 to separate a mixt. of n-hexane, methylcyclohexane, cyclohexane, iso-PrOAc, 2-pentanone, and 4-Me-2-pentanone in CSz soln. Kitamura and Seko (82L)also discussed GC trace analysis for separating a trace component which appears as a shoulder on the tail of the main sample component peak. A dual-column system was used and the sample contg. the impurity was injected into one column, a reference being injected into the second column under conditions so that the tail of the reference peak coincides with the tail of the principal component peak. A timin device is used to permit the reference material to be injecte at a fixed time after the injection of the sam le so that peak time-matching can be achieved. By use of a Zifference signal from the detector, only the impurity peak will appear in the chromatogram. By use of a 2-m sample column of P6-15008 and a 1.5-m reference column packed with DNP and C H8 as reference, benzene contg. 1 ppm PhMe was Andersson and Ericsson (9L) determined the mean timetemp. rofile in a sample subjected to pyrolysis GC in order to estatlish whether it is ossible to equate the temp. of the pyrolyzer with that of t e sample being pyrolyzed. The degradation of cis-1,4-polybutadienewas studied by sequential pyrolysis. By use of measured rates of degradation for different amounts of sample, determination of the temp. dependence of the degradation rate from an Arrhenius plot, and combination of exptl. results with theor. derived expressions, the time-temp. profiles of different amts. of sample could be calculated. Choosing the a propriate pyrolysis conditions of sample thickness, time, anftemp. of the sample is nearly the same as that of the pyrolyzer. Zizin and Makov (175L) designed two units for the thermochromatographic (Tg) variant of GC analysis using water as heat exchange medium. Temp. ranges of 0-100 "C or 0-150 "C (under higher pressure) are available. The method changes the temp. gradient of the column and ives better sepn. coefficients than conventional methods as femonstrated by sepn. of aromatic HCs. The TG effect and the effect of temp. programming are discussed.
d
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Liquid Chromatography. A number of papers were published in the field of LC. Hirata and Novotny (67L)found that packed capillary columns of the reversed-phase type for LC provide the high efficiencies needed to resolve complex mixts. Small volume samplin and detection are design problems that must be solved. direct method of sampling is demonstrated that compares favorably with splitting injection. Two step-wise gradient elution techniques were developed for these columns. With small volume UV and spectrofluorometric detectors, a standard mixt. of toluene, naphthalene, fluorene, anthracene, pyrene, chrysene, and benzo[e]pyrene was separated. The method was then applied to polyaromatic fractions from coal tar. Freeman and Schram (4115) derived in numerical form a sin le expression relating liquid gel permeation with alkane mo!. size (L) including the conformational coefficient (ZJ. L = 3.26 + 0.0358MW - 0.202i. The value Z i is constant for each structural isomer group. Values of Zi for the following alkane series are tabulated n-alkane, 2-Me, 3-Me, 4-Me, 3-Et, 4-Et, 2,2-Me22,3-Mez 3,3-Mez. Hennion et al. (66L)studied the influence of the number and length of alkyl chains on chromato raphic roperties of hydrocarbonaceous bonded phases. {arious Jkyltrichlorosilanes (C Cl8) were bonded to porous silica and the products were s f r y packed in LC columns (4.8 mm X 15 cm). For octodecyltrichlorosilane at 111"C, 18 h were required to achieve max. C content in the packing. Higher temps. gave greater loading more ra idly. Capacity factors for a series of polycyclic aromatic H d and henols increased exponentially with the C content of the C18 rionded phase up to 15%. The selectivity factors also increased with C content and column efficiency was max. at about 14.5% C. For bonded phases with different alkyl chain lengths, the capacity factor for hydrocarbons increased exponentially with chain length; for phenols this increase was rectilinear. Increasing the polarity of the mobile phase (0 to 30% H 2 0 in CHBOH) increased exponentially the capacity ratios for the HCs and the selectivity factors. For best results, a Clgbonded phase with a coverage of about 2 pmol m-3 should be used. Hammers et al. (61L)discussed the standarization and determination of selectivity of octadecylsilylsilica in LC. The adsorbent was prepared by treating Merckosorb Si 60 with trichlorooctadecylsilane (surface coverage 1.64 pmol m-2 and was acked into a column (2.1 mm X 25 cm). Retention data on t e column were measured for a range of mono- and disubstituted benzenes, polycyclic aromatic HCs, and substituted hexanes and cyclohexanes. The eluents were hexane, hexane-CH Clz (137), and CH C12. Factors affectin retention were consi8ered mathematicdl , Ageev et al. (5Lf prepared columns for LC with sepn. efgciencies of 20000 to 40000 theoretical lates/m (chromatograph Tsvet 304). The adsorbents (siica gel S-3, Silochrome S-80 and S-120, were fractionated by sedimentation in HzO. The construction of the fillin device and the method of filling the column was describecf The efficiency was tested by using mixts. of c6&, phenanthrene, PhN02,and Ph NH. Tables give the number of theoretical plates for the sorbents, their different particle sizes, and application procedures for different samples. Hammers et al. (62L)investigated the adsorptive ro erties (CNA-&car for a of N-2-cyanoethyl-N-methylaminosilica large number of mono- and disubstituted benzenes and some unsubstituted polycyclic aromatic HCs when CNA-silica was (13:7) used for LC with hexane, CHzCl , or he~ane-CH~C!~ as mobile phase at 25 and 43.5 The results are discussed in relation to the adsorption mechanism and are compared with those obtained on ODS-silica. Kostyla et al. (86L)used chemically modified solid polymeric supports contg. specific functional groups for the sepn. v d or concn. and detection of selective classes of org. com ds. via LC, Pyrrolidone on vinyl modified silica was u s e l to separate aromatic compds., an organomercurial group on agarose to separate mercaptans, and the diazonium functionality on a solid supporting resin for separating phenols and arom. amines. Use of the supports for chromatographic sepn. was discussed. Halasz (6015)described a procedure for fractionating vacuum residues from several crude oils (Boscan, Safaniya) by LC. The following were discussed briefly: nature and pretreatment of column packing, water content of heptane, eluting solvents, column capacity, accuracy, and repeatability
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of the method. The method does not apply to gas oil and other light petroleum fractions since 90% of these oils eluted in the first two fractions. Semonian et al. (141L)described the use of positive pressure columns for solvent cleanu or LC. The formation of gas bubbles, the loss of solvent gy evaporation and the contamination by H 0 vapor that occurs when gravity-feed columns are used can 'be minimized by using a closed system in which the solvent itself provides a protective gas cover. A column of silica gel having a stopcock (at its lower end) leading to a receiver was connected a t its upper end to the solvent reservoir. The reservoir was connected via a T to a vent and to a mercury vessel for regulating the pressure. The equipment was used to purify pentdne. Joecker and Smink (72L) discussed the selection of the optimum system and detectors for the detection of aromatic substances via LC. Schick and Huber (136L) patented.an amperometric sensor for LC using metal oxide hydroxide electrodes. The working electrode consists of a transitionmetal substrate having a surface layer of a multivalent oxidelhydroxide of the metal in which the anionic vacancies in the coating are partially filled with halide or sulfide ions. Applications include the detn. of mono- and polyhydroxy aliphatic and aromatic compds., aromatic and aliphatic amines and thiols, and H 2 0 Lower detection limits for glucose at a Cu oxide-hydroxi%e working electtode were 100-500 pg. Vidrine and Mattson (163L)described a practical real-time Fourier transform IR detector for LC. Sample flow cell detection with automatic solvent subtraction is used and detection of 500 ng of injected paraffin oil was demonstrated. Results from LC runs were used to illustrate system capability. IR s ectra can be acquired simultaneously. Vidrine (162L) use subtractive techniques in interpreting on-line Fouriertransfor IR spectra of LC column eluates to permit the identification of o-xylene in a chromatographically incomplete sepn. of a com. rn-xylene contg. small amounts of p - and o-xylene and the identification of CC14 and toluene as contaminants in an incompletely resolved chromatogram of polystyrene. Li and Arrington (9OL) used a dual-wavelength spectrophotometer as a high-resolution, high-precision, high-selectivity detector to overcome peak overlapping and provide quantitative sepn. of a mixt. of polycyclic HCs via LC. The sepn. was carried out by using a column packed with pBondapak CI8 at 37 "C with 74% CH30H as the mobile phase. Positive identification of the HCs was assisted by (1) computer-simulated chromatograms from chromatographic and spectral data obtained under different conditions and (2) use of equations derived from the transient absorbance during elution and from the difference in absorbance a t the two wavelengths. Stoveken and Vitali (150L)discussed in detail the general principles of LC with a spectroscopic detector and applications to HC sepns. They used Perkin-Elmer's Series 2 and Series 3 LC with: (1) the Model LC-55 variablewavelength UV detector fitted with an accessory for recording the spectra, (2) the Model Lc-15 fixed wavelength UV detector, (3) the Model LC-lo00 fluorescence detector. Examples of spectra include tert-butylbenzene, benzene, toluene, ethylbenzene, and isopropylbenzene. Colin et al. (29L)described the construction and performance of an improved differential refractometer detector for LC. Design modifications over conventional RI detectors include the following: (1)symmetrical design and small focal lengths; (2) placing the double prism in a parallel li ht beam making it less sensitive to vibrations; (3) a cod-source light-emitting diode (G& TIL 31) emitting at about 940 nm with a bandwidth of 45 nm minimizes base-line shift by reducing differential heating of the two cells by the source; (4) designing the cell block for easy removal and thus simpler maintenance; (5) small cell volume which reduces band broadening. The detector has a time constant of 24 ms and a linear dynamic range of 27 OOO. The equipment is compared with a Waters R 401 detector. Under optimum conditions 1 pm of benzene in heptane can be detected. Fallick and Rausch (38L)described the radial compression technique for packing LC columns with small particle size packings which permits the reproducible formation of a homogeneous bed and eliminates wall effects. Performance of this packing technique and the LC system thus obtained is illustrated with the sepn. of arom. HCs and other org. compds.
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Mills et al. (IO1L) described the use of a general purpose microcomputer for flexible automation of LC. Hardware was constructed from a set of ready-made circuit boards. Control programs were written in assembly language and the datahandling program in CORAL 66. The system had facilities for automatic repetitive sampling (coeff. of variation of 1%) and means for implementing rinse and purge routines. A dataprocessing algorithm ensured quantitative results even for poorly resolved peaks. Chromato ams for six arom. HCs are given. Majors (96L)discussed app 'cation of the Varian Model 5000 (microprocewor-based LC with CRT display) to the sepn. of polystyrene oligomers, using the 3-solvent capabilities of the unit. The advantage of the units' automatic loop valve in monitoring the course of a chemical reaction is also discussed. In addition to GC and LC, a number of other analytical techniques were covered. Adrian (2L) reviewed the prepn. of samples for IR spectroscopy by means of suspension in paraffin oils and their derivatives. Miyashita et al. (102L) developed an automated quant. IR system by coupling an IR spectrophotometer and an on-line minicomputer. A leastsquares polynominal of degree two was used to calculate the smoothed transmittance in real time. After a sample was measured, solvent com ensated transmittance data for quantitative detn. were oEtained. This system is suitable for programmed wavenumber scanning control because of the high wavenumber reproducibility of the spectrophotometer. Three isomeric xylenes were detd. precisely with this system. Grasselli (5015) described the development of analytical methodology and the application of various analytical techniques to analyze a deposit in a gasoline tank truck (IR spectroscopy), structural analysis of a Co molybdate-on-alumina hydrodesulfuriation catalyst (Raman spectroscopy), and an engine valve deposit that was suspected of being a motor oil additive (complex IR spectroscopic scheme). Kekedy and Kormos (79L) reviewed the roperties and a plications of a semiconductor electrode base on SnOz. This e6ctrode consists of a layer (1-2 pm) of SnO, coated on glass, which has high conductance. Electrochemically it behaves similarly to a Pt electrode but can be used over a wider potential range (2300 mV). This electrode has been used as the working electrode in potentiometry, chronopotentiometry, coulometry, and stripping anal sis. I t also forms the basis of electrochemical sensors for 60,0, acetone, or HCs. Kawala et al. (7815)discussed the use of molecular distn. for analytical and preparative sepn. of high-boiling petroleum fractions. Preliminary single-stage sepn. of less volatile components and further sepn. of more volatile components into narrow-boiling fractions using a multistage unit were used to separate the atm. residue of Romashkino oil. Zygmunt and Staszewski ( I 16L) described the use of Na 4-chloromercuribenzenesulfonate (I) in ethanediol-H20 (1:l)to extract and concentrate RSH from petroleum HCs. In the extn., I forms mercaptides with RSH; the extracted mercaptides are then regenerated by treating the extract with aq. 3.8% thioacetamide and are removed by extn. with hexane or hexanebenzene (91)with recoveries from 96 to 99%. This procedure might be used as a preliminary to the GC detn. of individual thiols in gasoline cuts. Jenkins (71L)discussed the use of XRF (energy-or wavelength-dispersive) to provide a reasonably complete elemental analysis which in turn is used to greatly simplify phase analysis by powder XRD. Computer 'search-matchin of data can be improved considerably where both positive an8 negative elemental information are available. Application of combined XRD-XRF for routine phase analysis of leaded asoline engine deposits and airborne particulates is described. nstrumentation is discussed. Arkenbout (11L) reviewed the advantages of continuous fractional crystallization for the sepn. and purification of org. compds. from theor. and ractical standpoints. Applications include the sepn. of xyEne isomers and thiophene from benzene and the purification of benzene. Several lab-scale devices are described and scale-up to pilot plant scale is mentioned. Nechitailo (I12L) described the development of thermal analysis (TA) and its application to petroleum chemistr characterized Soviet and foreign TA equipment, and m a l l an extensive lit. review. Potential a plications and results of TA analysis were discussed for H8compos. of crude oils,
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ANALYTICAL CHEMISTRY, VOL. 53, NO. 5, APRIL 1981
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melting temps. and purity of HCs, phase diagrams of mixts. of n-paraffins, thermal stability and structure of adducts of urea and thiourea with n-paraffins and isoprenoid HCs, characteristics of lubricants and mechanism of their oxidation, various synthetic lube additives, greases and soap thickeners, petroleum asphaltenes and resins, prepn., compos., and props. of catalysts, and physical and chem. processes in polymers, 108 references. Tittarelli (155L) reported on recent trends, developments, and Petroleum Industry applications in flameless AA spectroscopy, as given in the jointly held 20th Colloquim S ectroscopicum Internationale and the 7th International 8onference on AA (Prague 8-30 to 9-3-77). The following are discussed: mechanisms of atomization and of the loss of atomic vapor in the atomizers; results of de Galen’s study of the Perkin-Elmer HGA-2100 and Varian-Techtron CRA-90 atomizers which showed that current efficiencies and sensitivities could be improved considerably; methods of correcting for background absorption (including FM continuous light and echelle-grating monochromators) to permit the analysis of concentrated solns. and eliminate noise from the light source and flame. Also discussed extensively is a U S . oil company trace metals project (Anal. Chem. 1974) which described methods for Mn, Hg, Cd, and Be in petroleum products. Lukasiewicz (95L)described the use of relatively transparent flames produced with N20/H2in AA for direct analysis of petrochemical and petroleum products for trace nonrefractory elements without prior sample diln. The analysis of gasoline indicated that litle N 2 0 band absorption remains when mass transport of organic solvent to the flame is high. Correlations between the decrease in absorption of N20/H2flame at 205.2 nm and the following were found: (1)the amount of C delivered to the flame gasoline, isooctane, acetone, methyl isobutyl ketone, and 2-propanol; (2) the product of the b.p. and heat of vaporization at the b.p. for relatively nonpolar solvents such as isooctane, cyclohexane, benzene, acetone, toluene, methyl isobutyl ketone, xylene, and several alcohols and nalkanes. Robinson (129L)discussed the potential difficulties in using carbon atomizers in AA, includin factors affecting the rate of atomization and background a%sorption and detection and correction. Detection limits for 34 elements are given. The use of gas ((20,)lasers in studying volatile organic compds. is also considered, and applications are discussed. Detection limits with a prototype instrument are
