Organic elemental analysis - ACS Publications

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Organic Elemental Analysis T. S. Ma Department of Chemistry, City University of New York, Brooklyn, N. Y. 7 7270

Milton Gutterson Flavor Applications Laboratory. Dragoco, lnc., King Road, Totowa, N.J. 075 72

This review follows t h e previous one (189) a n d covers the literature and information received by t h e authors from October 1971 to November 1973. As in the past, it surveys the developments in t h e determination of the elements in organic materials. Since the commercial C H N analyzers have been on the market for some ten years (186), time is come for a n overall evaluation of these automated machines. At the International Symposium on Microtechniques held in University Park, P a . in August 1973, several practicing microanalysts reported on the performance of the respective apparatus which they had used for long periods. The findings are favorable. At t h e same time, it is noted t h a t the number of commercial instruments (187, 188) has diminished. Research activities on automation, however, have been vigorous, as evidenced by t h e papers on coulometric methods, use of ion-selective electrodes, and other electroanalytical techniques. A new direction involves computerization, which permits the selection of a suitable method, analysis of t h e sample, and d a t a processing to be carried out automatically. The recent public attention on pollution control and environmental protection has produced many publications on trace analysis, such as the determination of mercury and lead in foods, and harmful organics in the air. Now t h a t t h e general interest has been shifted to the energy crisis. t h e emphasis on analytical research is expected to change. Nevertheless, the microchemical approach (185) will remain t h e guiding principle, which is concerned with using the minimum quantity of working material to obtain the desired chemical information. Thus, two instruments recently commercialized are worthy of note: the Elemental Analyzer of Chemical Data Systems ( 4 3 ) which can perform simultaneous C, H , N, and 0 determinations with one sample weighing 1-200 pg, and the Mettler-Heraeus Automatic Nitrogen Analyzer (210) which is suitable for the analysis of both pure organic nitrogen compounds and trace nitrogen in organic materials.

CARBON A N D HYDROGEN Main interests seem to be threefold: techniques for completely automating t h e analysis, processes to reduce t h e time, a n d methods for handling difficult samples. Binkowski (20) described a combustion train in which the samples were decomposed at approximately 1050 "C in a stream of air and oxidized over a layer of cupric oxide. Time for a determination ranged from 14-16 minutes. Thuerauf and Assenmacher (310) combusted the sample over oxygen in the presence of cupric oxide. The carbon dioxide formed was determined by a nondispersive infrared absorption technique. T h e water in the exit gases was trapped by freezing, subsequently evaporated, converted into carbon dioxide, and measured by the same IR technique. Koslowski, Kobylinska-Mazurek, and Biziuk (164) modified t h e conventional flash-combustion chamber to increase its capacity. In many semi- or completely automatic procedures, a coulometric finish has been proposed. Nakamura, Kuboyama, Ono, and Kawada (222) separated the combustion gases on a chromatographic column. The carbon dioxide was converted into water over lithium hydroxide and passed into a hygrometer and electrolyzed in a diffusiontype platinum-PzOs cell. The water from the hydrogen in the sample was similarly determined. The water contents were analyzed by a blank-free method, with a n electronic

digital integrator and automatic recording. Floret (89) modified a previously described procedure. The water was frozen out and the carbon dioxide determined coulometrically. T h e water was subsequently converted t o carbon dioxide by passage over NW-carbonyl-diimidazole and analyzed similarly. Fraisse (92) after titrating the liberated carbon dioxide coulometrically, released t h e frozen water by heating, converted it to carbon monoxide and then to carbon dioxide which was determined by the same coulometric titration. Ieki and Daikatsu (142) applied the technique of differential thermal analysis to a gravimetric method for carbon and hydrogen. The sample was placed into a silica tube on a thermocouple detector and burnt in a stream of air or nitrogen. An empty tube was heated in a 'parallel reference system. Any changes in the sample were recorded as endothermic or exothermic peaks on the thermogram. The thermocouples were enclosed in t h e oxidizing catalyst, with additional thermocouples in the carbon dioxide and water absorption tubes. Krivolapov, Rusaev, and Antonov (170) utilized reaction gas chromatography. The sample was placed in a stainless steel combustion tube mounted vertically and containing cupric oxide. The sample was pyrolyzed in a stream of nitrogen or helium. The combustion gases were swept into a V-shaped gas-chromatographic column and the resulting carbon dioxide and water were detected with a katharometer. Trutnovsky (316) described a technique for automatically weighing the a b sorption tubes in a gravimetric procedure for carbon and hydrogen. Ratcliffe and Cunninghan (256) combusted solid fuel samples in a silica combustion tube heated by two movable furnaces using purified oxygen. The movements of the furnaces and the oxygen flow rate were automatically programmed to give optimum combustion conditions. Merz, Brodkorb, and Kranz (208) described the application of electronic data-processing to the carbon and hydrogen analyses. Carbon was titrated as COz after combustion and the liberated water was converted to CO and then COz and titrated similarly. The results were fed to a computer for evaluation. Pechanec (239) investigated various catalytic packings with the view of suppressing nitrogen dioxide formation in organic nitrogen-containing compounds. He concluded t h a t a layer of Crz03 in the packing was advisable. Synek, Vecera, and Kratochvil (297) proposed a universal method, especially for compounds containing fluorine, phosphorous, or silicon. The recommended packing absorbed interfering products of combustion, and the carbon dioxide, water, and any oxides of nitrogen were then absorbed in a special apparatus. Tonkovic and Mesaric (314) recommended a layer of thorium oxide (alone or mixed with silica gel) for fluorine-containing compounds. For organic substances containing sulfur and halogens, Mikhailova and Khromov-Borisov (211) absorbed the silver sulfate and silver halides produced in the Pregl combustion method in a layer of powdered quartz. Xogteva and Yatsina (225) combusted samples containing antimony, chlorine, phosphorus, and nitrogen under a layer of AgZW04 plus ZrOz. After the combustion, t h e oxides of the ashforming elements remained under the catalyst layer and the carbon and hydrogen were determined in the conventional gravimetric manner. Bazalitskaya and Alekseeva (14) absorbed interfering combustion products from Samples containing antimony and arsenic in a layer of MgO and CuO, heated at 200 "C for antimony-containing compounds and 25-30 "C for arsenic-containing samples.

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Wojnowski and Olszewska-Borkowska (341) described a procedure for carbon and hydrogen in sulfur-containing organo-silicon compounds. T h e sample was mixed with Co304 and heated at 920-950 "C in purified oxygen. The combustion products were passed over catalysts of platinized asbestos, Co304 on corundum and silver. The carbon dioxide and water were determined gravimetrically. Celon (42) recommended the use of aluminum capsules and combustion in dry helium at 1150-1200 "C for air-sensitive solid compounds, the capsule being covered with a catalyst mixture. For the element carbon alone, Fraisse (90) decomposed the sample rapidly and, after removal of interfering combustion products, t h e carbon dioxide was drawn into the cathode compartment of a coulometric cell containing aq. B a ( C 1 0 4 ) ~maintained a t p H 9. T h e liberated H+ was titrated coulometrically. The same author (91) determined hydrogen alone by a modification of the above procedure. The water formed in t h e combustion was reacted with carbon a t 1120 "C to produce CO which was converted to CO:, by passage over CuO a t 450 "C. The COz was then titrated coulometrically. The precision of both methods was superior to t h a t of conventional methods. Other workers have proposed methods for hydrogen only in organic compounds. Fedoseev and Baidulina (83) decomposed the sample by catalytic oxidation and reacted the water produced with activated magnesium to liberate hydrogen; the volume of which was then measured. Liederman and Glass ( i 7 9 ) proposed torch combustion for hydrogen in liquid hydrocarbons. The water produced was collected in an absorber containing M g ( C 1 0 4 ) ~Glass . and Cowell (109) pyrolyzed the sample in a stream of nitrogen over CuO as catalyst. The oxidation was completed in a stream of oxygen, interfering substances were retained by a silver vanadate packing and t h e liberated water was determined gravimetrically in a Mg( C l o d 2 absorber. Bresler, Kogan, Shumakovich, and Gel'Fan (28) described an apparatus for the determination of hydrogen consisting of a coulometric cell (of the electrolytic-hygrometer type). After combustion, the products were passed into a cell containing plati 7um electrodes coated with H3P04. A lumber of procedures have appeared for isotopes of carbon and hydrogen. Hilton, Nomura, and Kameda (133) modified a n oxygen bomb procedure for radioactive carbon. 14C02 was absorbed in the bomb solution and Ba14C03 was precipitated directly in the scintillation counting vial. Bock and Thier (24) studied the sources of error in the determination of carbon-14 after closed-flask combustion and scintillation counting. The major source of error was incomplete combustion, the CO formed not being absorbed. Fraisse, Girard, and Levy (94) determined deuterium by freezing out t h e deuterium oxide formed after combustion of the sample. The frozen DzO was vaporized, reduced to D H over magnesium, and measured by thermal conductivity. Frohofer (96) analyzed samples containing carbon-14, tritium, and deuterium by pyrolyzing in a stream of nitrogen, then by combustion in a stream of oxygen. The 14C02 was absorbed in ethanolamine-methanol for scintillation counting. The tritium was frozen out in liquid CO:, as water and then later determined by scintillation counting. The deuterium was analyzed from the intensity of the IR band at 2000 c m - , measured on the trapped 2HzO. Huelsen (141) developed a fully-automatic sample-combustion apparatus for the determination of hydrogen-3 and carbon-14 in the liquidscintillation spectrometer. The samples were contained in vessels mounted on a disk. Rotation of the disk and the beginning of the cycle were triggered by the pre-set time interval of t h e liquid scintillation counter. On signal, the sample carrier was depressed into the combustion vessel, combustion was started electrically, and the products were absorbed in methanolic ethanolamine. This solution was run out into a vial containing scintillator solution. The vials were transported on a belt-drive to the counter.

form followed by a hollow cylinder of platinum foil filled with 30% platinized asbestos finely c u t and ignited. Lapteva, Novikov, and Bondarevskaya (174) developed an a p paratus for the simultaneous determination of two samples in parallel combustion tubes with programmed heating. Fedoseev and Baidulina (81) eliminated the need for sweeping with carbon dioxide in an apparatus comprising a silica combustion tube sealed a t one end, a tube containing Mg( Clod):,, a t r a p containing 50% potassium hydroxide solution, a vacuum pump, and a micro-eudiometer. The combustion tube was evacuated and combustion took place in a closed system. The combustion products were subsequently pumped through the Mg(C104)? and the KOH solution, and the nitrogen was collected in the micro-eudiometer. Gel'man, Larina and Chekasheva (107) suggested the use of lead oxide for difficultly combustible compounds. The sample in a silica container was covered with PbO-NiO (l:l), the rest of the container filled with granular NiO and placed in a conventional, packed combustion tube. Kuebler, Padowetz, and Pave1 (171) modified the Merz automatic apparatus to permit the combustion tube to be flushed with oxygen and vented before the reduction tube. Sels and Demoen (279) proposed modifications to the Coleman nitrogen analyzer involving both the combustion and reduction systems and also developed a n improved end-point detection system. Various changes and modifications have also been proposed to the Kjeldahl nitrogen determination. Pic0 and Calvo (246) described an apparatus for the automated agitation of Kjeldahl flasks during the digestion process. Kramme, Griffen, Hartford. and Corrado (165) developed a n automated, comprehensive method which could be employed without modification regardless of the composition of the sample. Harwood and Huyser (121) constructed a manifold with Technicon units for the automated distillation of ammonia from the acid digest. There was good agreement between the automated and manual methods. Srivastava and Mann (288) proposed a simple apparatus for the distillation step which gave a smaller error than the results obtained with the Pregl-Parnas-Wagner apparatus. Odland (230) described modification to a n AOAC method resulting in a shorter time for the analysis. McDonald, Crowley, and Clinch (203) digested plant samples in borosilicate glass test-tubes inserted into a gas-heated aluminum block a t 330 "C. Fedoseev, Vladimirova, and Osadchii (84) heated the sample with Devarda alloy in a glass tube placed in a furnace a t 550-600 "C. Finally the alloy was heated with 0.1N sulfuric acid and the nitrogen determined as ammonia by a conventional method. Grappin, Jeunet, and Rigogne (112) compared their apparatus for the automated determination of nitrogen in milk based on the Amido black dye-binding method to other procedures, such as the Kjeldahl, and found the results to be similar. Greenaway (123) compared the Kjeldahl, dye-binding and biuret methods for protein in wheat flours. The Udy dye-binding technique differed from t h e others, and a new conversion table was proposed to bring the values into good agreement with Kjeldahl and biuret results. Gantenbein (99) found t h a t a previously described automated procedure was suitable for meat products. A number of techniques involving neutron-activation analysis have been described. Geisler, Maul, and Panse (105) studied the blank value in samples containing hydrogen and oxygen. It was concluded that, in practice, a rectilinear relationship between the blank value for nitrogen and the product of the oxygen and hydrogen content could be used. Brune and Arroyo (29) applied the technique of fast-neutron activation analysis to the nitrogen content of grains with good agreement to the Kjeldahl method. Tiwari, Bergman, and Larsson (311) developed a technique in which the sample was irradiated by a Be24lAm source applicable to small samples of grain.

NITROGEN A number of modifications and improvements to the Dumas method have been published. Saran, Khanna, and Banerji (270) proposed a new filling consisting of a layer of reduced copper between layers of cupric oxide in wire

The automation of the procedures for the determination of oxygen in organic compounds has drawn considerable interest. Karrman and Karlsson (157) used the Unterzaucher method and passed the iodine vapor corresponding to the oxygen content into a coulometric cell where

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ANALYTICAL CHEMISTRY, VOL. 46, NO. 5, APRIL 1974

T. S. Ma is professor of chemistry at Brooklyn College of the City University of New York. He received his PhD degree in synthetic organic chemistry from the University of Chicago in 1938 and began his career as a teacher of microchemistry at Chicago. Subsequently, he established microchemistry laboratories and taught at National Peking University, China; University of Otago, New Zealand: and New York University. Dr. Ma has been particularly active in promoting the application of microchemistry to research and education and has lectured widely on this subject. Professor M a has many publications, including a book "Organic Functional Group Analysis," (Wiley, New York, N.Y., 1964), the chapter on "Quantitative Microchemical Analysis" in "Standard Methods of Chemical Analysis," the section on "Organic Qualitative Analysis" in "Handbook of Analytical Chemistry." the chapter on "Organic Analysis: Fluorine" in "Treatise on Analytical Chemistry," and "Analysis of Carboxylic Acids and Esters" in "Chemistry of Carboxylic Acids and Esters." He is an editor of Mikrochimica Acta, the international journal on microchemistry and trace analysis. He also serves on the Editorial Boards of Microchemical Journal and Journal of Environment Analytical Chemistry. His current research interests are concerned with organic synthesis and analysis on the mg to p g scale, the use of smallscale experiments to teach chemistry, and microchemical investigation of medicinal plants.

Milton Gutterson received his BS degree from the City College of the City University of New York in 1949. After graduation he worked for Popsicle Industries (formerly Joe Lowe Co.) Division of Consolidated Foods Corp.. Englewood, N.J., where he was chief chemist and then plant manager. He has since worked for Ehlers Division of Brooke Bond Foods Inc. He is now connected with Dragoco, Inc., Totowa, N.J., where he is director, Flavor Application Laboratory. For several years he was a parttime lecturer in the graduate division of Brooklyn College, City University of New York. where he supervised the laboratory for quantitative elemental and functional group microanalysis. He earned his master's degree from Brooklyn College in 1956 by attending classes and doing research after working hours. His special interest is in the field of organic microanalysis. He was adjunct professor of chemistry at the New York Institute of Technology, Manhattan Campus. evening division. Mr. Gutterson recently published several monographs on food processing with the Noyes Data'Corp., Park Ridge, N.J. These were titled "Baked Goods Production Processes, 1969," "Confectionary Products Manufacturing Processes, 1969," "Fruit Juice Technology, 1970," "Fruit Processing, 1971," and "Vegetable Processing, 1971 ." He is a member of the ACS, the American Microchemical Society, the American Association of Cereal Chemists, and the Institute of Food Technologists.

the iodine was reduced a t a controlled potential a t a rotating platinum electrode. The number of coulombs consumed was measured by a n electronic integrator with a digital voltmeter. Merz (207) described a system for analysis in which the entire cycle of operations took place automatically and the readings obtained were fed directly into a computer, which presented printed results, The same author (205) developed a n apparatus involving parallel operation of two pyrolysis assemblies, two automatic titrators, a print-out desk calculator, and a n electrobalance. Erroneous determinations were kept t o a minimum by individual programming of the apparatus according to the pyrolysis properties of the test compounds. Pella and Colombo (242) utilized the technique of pyrolysis-gas chromatography. The sample was pyrolyzed in a stream of helium, the oxygen converted into CO over a special form of carbon a t 1000 "C, and separated on a column of molecular sieve 5A with katharometer detection. Roemer, van Osch, Buis, and Griepink (261) described a procedure for the automated determination of milligram amounts of carbon dioxide. The carbon dioxide produced was absorbed into a solution of 0.5M BaClz in tert-butyl alcoholwater (1:9) a t p H 10. The solution was automatically titrated back to p H 10, the end point being indicated electrometrically. Shimizu and Hozumi (281) studied the thermal decomposition of organic compounds in a n automated oxygen analyzer by a previously described optical integration method. In the analyzer, with argon as a carrier gas flowing a t -20 ml per min. and the carbon layer (16 cm long) a t 1050-1100 "C, even aromatic compounds of low reactivity were completely converted into CO. For compounds containing sulfur, Chumachenko, Khabarova, Egorushkina, and Ivanchikova (48) found t h a t pyrolysis of the sample a t 1100-1150 "C under a layer of carbon in a sealed vessel did not lead to the formation of COS and all of the oxygen was converted into CO which was measured by the peak height obtained by gas chromatography. Campiglio studied various methods for the removal of carbonyl sulfide and carbon disulfide from the pyrolysis gases in sulfur-containing compounds. The physical methods tested (34) were as follows: (i) condensation a t -77 "C (acetone-solid C 0 2 ) ; (ii) freezing out a t -196 "C (liquid N ) ; (iii) adsorption on paraffin wax. Method (ii) was the only effective one. The chemical methods (35) tested were sodium methoxide on pumice, glycerol saturated with KOH (alone or on silica gel), ethanediol, decylamine, and ethanolamine. Although none of the chemical methods were completely effective, all but decylamine reduced the interference to tolerable limits. Ethanolamine was the most efficient reagent. Metals (36) were also uti$zed to eliminate the interference of sulfur. Zinc a t 350 C was effective, as was nickel a t 600 "C. Copper a t 900 "C and silver a t 800 "C were less active. The same author

(37) prevented the formation of CS2 and COS by using a mixture of nitrogen containing 10% hydrogen as the carrier gas. Volodina, Terent'ev, and Besada (329) modified a reduction method for oxygen to make it applicable to halogen-containing compounds. Pyrolysis took place in a stream of nitrogen and hydrogen gases; a layer of Ag4Fe(CN)G was included between the pyrolysis tube and the hydrogenating catalyst (nickel on pumice). The water produced was absorbed on anhydrone. The same authors (330) utilized their method for organofluorine compounds, with a layer of anhydrous barium chloride for absorption of the hydrogen fluoride produced during pyrolysis. The HC1 liberated in this reaction was absorbed by the layer of Ag,Fe(CN)e.

HALOGENS Many procedures have appeared describing methods for shortening the time of analysis and automating all or part of the analytical steps. Scheidl and Toome (273) combined a combustion furnace, a buret, and a titrator to form an automated assembly. A solid-state programmer functioned to complete the analysis in less than four minutes. Automation involved the steps of combustion, feed of reductive flush solution, filling of the titration vessel, and titration. Calme and Keyser (32) based their method on the reaction of the combustion gases with ozonized silver iodide. The liberated iodine was absorbed in a buffered solution of sodium iodide and titrated automatically using sodium thiosulfate solution. Kainz and Mueller (153) passed the products of combustion into a titration vessel containing H S 0 3 - solution and a known molarity of Ag+. The halide ions formed were titrated automatically with Ag+ in the presence of a silver electrode to restore the potential of the cell. Volodina and Moroz (324) heated the sample in a stream of NHa at 750-800 "C and titrated the liberated ammonium halide by conventional methods. Kozlowski and Kobylinska-Mazurek (163) decomposed the sample in the presence of NH4HS04 in a stream of moist oxygen. The halogens were caused to displace iodine from AgzOIz and the liberated iodine was absorbed onto silver granules. If sulfur was present, its combustion products were retained by MgO. Trutnovsky and Sakla (317) burnt the sample directly in a stream of oxygen a t 950 "C. The products were swept into a second furnace a t 450 "C, where the halogens were absorbed onto silver wool. The apparatus was then swept successively with nitrogen and hydrogen and the hydrogen halides were collected in a flask containing water (or some HzOz for sulfur-containing compounds) and titrated by standard techniques. Strukova, Kashiricheva, Abdulina, and Kalashnikova (293) fused the samples containing ruthenium, rhenium, osmium, platinum, or palladium in a n oxygen bomb with sodium

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peroxide. The halides, after solution of t h e cooled melt, were titrated potentiometrically with silver nitrate solution (silver and calomel electrodes). Interference from palladium or platinum was avoided by masking with EDTA. Closed-flask combustion techniques continued to draw interest. Skorobogatova, Kravchenko, and Faershtein (285) recommended the addition of hydrazinium sulfate directly to the sample to prevent t h e formation of free halogens during combustion. Hassan (122) proposed the closed-flask technique for some highly halogenated compounds. After the combustion, the chlorine and bromine were determined iodimetrically by treating the solution with KI-KIO3 and titrating the liberated iodine with 0.02N-Na2S203. Steyermark, Lalancette, and Contreras (290) reported the results of a collaborative study which involved final titration of the ionic halides by mercuric nitrate solution. Corliss, Scholtz, and Wollner (50) used simple wrappers made from adhesive cellulosic tapes for both solid and liquid samples yielding results similar to sodium fusions for a series of chlorinated compounds. The types of wrappings should be chosen to suit the particular analysis. Cassat and Pont (40) developed a n automatic apparatus, arranged in a closed loop, consisting of t h e flask and a titration cell for Ag coulometry with null-point potentiometric end-point detection. The technique was applied to chlorine-containing compounds. For brominecontaining compounds, Machida and Utsumi (191) treated a n aliquot of the absorbing solution (alkaline hydrogen peroxide) with Hg(SCN)2 and Fez(S04)3.24Hz0 in acid solution and measured the extinction a t 460 nm. Lalancette, Lukaszewski, and Steyermark (173) determined iodine by a titrimetric method after the closed flask combustion. The absorbing solution (alkaline hydrazinum sulfate) was treated with hydrogen peroxide, adjusted to neutrality and the iodide ion titrated with 0.01N Hg(N03)2 and 1,5-diphenylcarbazone as indicator. For chlorine in quaternary ammonium chlorides, Dobrescu, Nartea, and Mercea (65) dissolved the sample and titrated directly with 0.1N AgN03 using a silver electrode us. the SCE. Potman and Dahmen (252) injected volatile compounds directly into a combustion train. The products of combustion were absorbed in acetic acid containing nitric acid and hydrogen peroxide in the presence of HgCl2 or HgBr2. The mixture was then titrated with 0.1N Hg2f using a n ion-selective electrode (Ag2S or AgI) us. a selected potential between a double-junction silver AgCl reference electrode. Quenum, Grandaud, Berticat, and Vallet (254) fused chlorine-containing polymer samples in a stainless-steel crucible with a mixture of sodium bicarbonate and sodium peroxide. The cooled melt was dissolved, treated with reducing agent, and the chloride was titrated with standard silver nitrate solution. Chumachenko and Alekseeva (46) subjected t h e halogen-containing sample to high temperature pyrolysis. For compounds also containing nitrogen or sulfur, the combustion products were separated on a gas-liquid chromatographic column, the interfering substances being eluted first, and then the halogens were passed into a conductivity cell containing mercuric nitrate solution and fitted with platinum electrodes. Aue, Gerhardt, and Lakota (8) used gas-liquid chromatography for halogen contents. The columns contained 10% Carbowax 20M or 10% OV-17 on Chromosorb W, H P (80-100 mesh) and they were operated with nitrogen as carrier gas and flame ionization or alkali flame detection. The halogen contents (chlorine, bromine, or iodine) were calculated from the results for the unknown and an added standard compound. The technique was also applicable to phosphorus-, nitrogen-, and sulfur-containing compounds. Havranek and Bumbalova (126) determined bromine in pharmaceuticals by means of X-ray fluorescence analysis. A pair of Ross filters (prepared from oxides of selenium and arsenic) with the use of the mixed emitter 147Pm/Mo ( p and X-ray emission) allowed the Selection of KZradiation for bromine. The closed-flask technique has been proposed for the combustion of various fluorine-containing compounds. Debal, Nabias, and Peynot (61) recommended that liquid samples be placed in a gelatin capsule with filter paper and 15 mg of glucose. For volatile samples, the fluorinecontaining compound was placed in a sachet of plastic (Terphane) and the glucose outside t h e sachet. Terry and

Kasler (304) used as absorbing solution a total-ionicstrength-adjustment buffer solution. The fluoride concentration was measured by using a solid-state fluoride ion selective electrode and referring the potential obtained t o a calibration graph. Hozumi and Akimoto (140) recommended a fluoride ion selective electrode incorporating a LaF3 single crystal (Orion Model 94-09A). The combustion took place in a silica flask (borosilicate flasks led to low results), buffer solution was added, and the mixture subjected to potentiometry with the use of a silver chloride reference-electrode. Meinert, Cech, Etzold, and Zoepfel (204) developed a colorimetric procedure in which a lanthanum-alizarin complexan solution was added to the absorbing solution. The extinction was then measured a t 635 n m and referred to a calibration graph. There was no interference from other halogens u p to 100-fold molar excess. Helesic (130) using a fluoride ion selective electrode and 0.01M La(N03)s to titrate liberated fluoride ions after closed flask combustion. Other techniques for t h e analysis of fluorine included t h a t of Volodina and Pivovarova (325) suitable for fluorinated polymers containing inorganically bound fluorine. The sample was pyrolyzed in a stream of ammonia a t 750-800 "C and the NH4F formed was determined by titration with thorium nitrate solution. For the determination of inorganic fluorine in addition to organically-bound fluorine, the sample was mixed with anhydrous ammonium sulfate before hydrolysis. For samples containing, in addition to fluorine, boron and phosphorus, Rittner and M a (259) proposed bomb combustion with a mixture of potassium nitrate-sucrose and sodium peroxide. After the addition of a total-strength ionic buffer solution ( p H 5 ) , the potential of the mixture was measured with the use of a fluoride-ion selective electrode. The amount of fluorine was calculated us. two standard solutions containing 10 and 100 pg of fluorine, respectively. Jones, Heveran, and Senkowski (149) dissolved the sample and treated a n aliquot with sodium biphenyl regaent. Finally, the emf of the adjusted solution was determined with a fluoride-ionselective electrode us. a calomel electrode. The fluorine concentration was obtained by reference to a calibration graph. Papay, Mazor, and Takacs (235) decomposed the sample in a stream of oxygen, retaining t h e fluorine on Pb304 as PbFz in a silica tube. The tube was transferred to a furnace a t 700 "C and steam was passed through it. The vapors were condensed, reacted with the thorium complex of chloranilic acid, and the free acid determined spectrophotometrically a t 530 nm by measurement of the violet color formed in the presence of Fe3+.

SULFUR, PHOSPHORUS AND A R S E N C For sulfur, Culmo (54) modified a Perkin-Elmer automatic C H N Analyzer (model 240). The standard combustion and reaction tubes were replaced by (i) a special tube containing WOs in the combustion zone (950-1000 "C) and one containing Mg(C104)Z outside the furnace; (ii) a reduction tube a t 820-880 "C containing copper wire to remove excess oxygen and halogens; and (iii) a tube containing 8-hydroxyquinoline to remove halogen by-products. The water absorption tube of the analyzer was replaced by one containing AgzO ( a t -230 "C) to absorb SO2. Debal, Levy, and Kolosky (60) described improvements to their previous method involving combustion and coulometry. The modifications were mainly in the combustion train to remove interfering substances and improve precision. Floret (88) employed reductive fusion with potassium in a metal bomb (Zimmermann method) for sulfurcontaining compounds. The liberated H2S was titrated automatically with 0.005M Hg2+ a t p H 9.4 under nitrogen, and interference from phosphorous and arsenic was eliminated by addition of zinc acetate or Arnd alloy. The H2S was distilled under nitrogen from the fusion melt after the addition of HCl-TiC13 solution. Binkowski and Wronski (21) eliminated the distillation step in the Zimmermann procedure by titrating the solution of the melt directly with 0.01N 2-hydroxymercuribenzoic acid and dithizone as indicator. Volodina and Martynova (326) pyrolyzed the sample in a stream of ammonia, using two furnaces a t 700 and 800 "C, respectively, and absorbed the products in 1N KOH, the S2- was then liberated and ti-

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trated potentiometrically with 0.01N ammoniacal AgNO3. The same authors (327) employed the above method for thiophene and its derivatives, using a catalyst layer to aid in the decomposition of the sample. Terent'ev, Bondarevskaya, Kirillova, and Potsopkina (301) determined sulfur in organotin compounds by coulometric titration with bromine electrogenerated from KBr in acetic acid medium. A number of procedures employing closed-flask combustion have been described. Gawargious and Farag (104) absorbed the products in a solution containing Ba(BrO+. The unconsumed Ba(BrO3)z was precipitated by adding acetone, redissolved, and determined iodimetrically. The amplification factor of the reaction is 12; the mean error was kO.170and the maximum deviation &0.2%.Gaux and Le Henaff (101) found t h a t adding a source of iodine (Le., iodoform) to the sample before combustion, ensured conversion of Sz- to S042- without treatment with hydrogen peroxide in the determination of sulfur by the barium perchlorate method. The precision of the modified method was equal to that of the standard method but the procedure was more rapid. Grigor'yan and Levina (115) added (NH4)2HP04 to samples of alkali salts of arene-sulfonic and -polysulfonic acids before combustion to ensure complete decomposition as some of the sulfur tended to be held on the surface of the platinum basket. The absorbing solution was titrated with 0.02N Ba(N03)2, using chlorphosphonazo I11 as indicator. Eliseeva, Dedkova, and Savvin (73) compared the closed-flask decomposition technique to that of oxidation by boiling with Hz02 in aq. NaOH, followed by titration of sod2-with 0.01N BaC12, using orthanilic K as indicator. The technique gave slightly lower results than the conventional method but was useful for the determination of small amounts of sulfur in organic solvents. Mullayanov and Obtemperanskaya (219) burnt sulfurcontaining samples in a stream of oxygen and the products of combustion were examined by IR spectrophotometry in a heated flow-through cell. Results were obtained from a calibration graph using dibenzyl sulfide as reference compound. Kirkbright, Marshall, and West (159) determined the sulfur content of oils by atomic-absorption spectrometry, using an inert-gasshielded nitrous oxide-acetylene flame. The sample, diluted with isobutyl methyl ketone, was directly aspirated into the flame which permitted evaluation of the sulfur content a t 180.7 nm. For phosphorus, the emphasis has been on automated methods, closed-flask combustions and other methods for decomposition of the sample. Johnson (146) in a collaborative study, compared the automated method of Gehrke et al. to the AOAC gravimetric quinolinium molybdophosphate method for phosphorus in fertilizers. Both methods yielded similar results, but the automated method was less reliable. Talbott, Cavagnol, Smead, and Evans (298) determined phosphorus in pesticide formulations by a semi-automated procedure. The phosphorus was extracted with 14% bromine in 80% acetic acid and analyzed colorimetrically by a modified AutoAnalyzer procedure. The results compared well to manual determinations and the precision was improved while the time for analysis was reduced. Nuti (227) recommended the use of a silica basket in a closed-flask procedure. The P043- was finally titrated with O.005M C o ( N 0 3 ) ~using Eriochrome Black T as indicator. Bishara and Attia (22) precipitated the Po43- in the absorbing solution (aq. NaOH-aq. Brz) with standard MOO^^^ solution (as quinolinium molybdophosphate) and determined the excess of molybdenum polarographically. Silicon and iodine interfered. Gawargious and Farag ( 1 02) determined Po43- in the absorbing solution by either (i) adding KI-KIO3 and titrating the liberated iodine with 0.01N NazSzO3; or (ii) adding NH4Cl-ZnS04 followed by KI-KIO3 and titrating as in method (i). Method (ii) was more accurate and gave a threefold amplification factor as three H + were liberated per mole of H3P04 by the artion of "4. and Znzf. The same authors (103) combined their methods for phosphorus in compounds containing nitrogen, sulfur, and halogens. Method (i) as described above caused liberation of iodine by acids formed from interfering substances and one proton from H 3 P 0 4 . This

titer was not recorded. Method (ii) was then applied and from this titer the phosphorus content could be calculated. Sympson (2967 recommended a coulometric titration after the closed flask combustion. The solution was neutralized to methyl orange and phosphoric acid was titrated with OH- electrogenerated a t constant current, while the p H was recorded as a function of time. The phosphorus content was calculated from the time interval between end points for H2P04- and HP042- and from the magnitude of the electrolysis current. Erickson (74) decomposed the sample with HzS04-fuming nitric acid-HC104 and precipitated the phosphorus as NH4MgP04 which was ignited and weighed as MgZP207. Lazarus and Chou ( 176) modified the method of Fiske and SubbaRow. The sensitivity was improved and 4-amino-3hydroxynaphthalene-sulfonic acid was recommended as reducing agent. Bigois (19) digested arsenic-containing samples with HN03-HzS04, followed by oxidation with Hz02. The As043- liberated iodine from KI. Excess sodium thiosulfate solution was added and the excess was titrated coulometrically, using iodine generated a t a constant current, with amperoinetric end-point indication. Antimony or copper could also be determined by this method. ORGANOMETALLICS Margosis and Tanner (200) determined mercury in pharmaceutical products by neutron-activation analysis. The y-radiation emitted by I97Hg a t 79 keV or by 203Hg a t 279 keV after irradiation was compared to a HgClz reference solution treated similarly. Terent'eva, Fedorova, Smirnova, and Malolina (303) modified the Schoniger flask to allow a reflux condenser to be mounted so t h a t dissolution of solid residues after combustion can be carried out a t elevated temperatures in the same vessel. The new flask was recommended for mercury, lead, iron, and cobalt in organic samples. Petukhov, Guseva, and Borisova (245) proposed a method for nickel in organic compounds which involved reduction with sodium metal, separation of the precipitated nickel, solution of the precipitate and either complexometric titration or photometric determination to complete the procedure. Heimes and Braun (128) digested organotin samples in a mixture of concd HzS04- fuming HN03-HC104; after dilution and adjustment of the digest, standard EDTA solution was added and back-titrated with 0.01N Cu(NO3)z using naphthylazoxine S as indicator. Bigois (18) determined manganese or chromium by digesting the sample with HN03-H2SO4; then manganese was oxidized with (NH4)zSzOs and chromium with HC104 in the presence of silver. The M n 0 4 - or Crz07*- produced were titrated with Fez+ coulometrically with a m perometric end-point indication. Panidi e t al. (234) applied the technique of X-ray fluorescence to the determination of iron and manganese. After excitation, the K radiation of manganese or iron was detected with a flowproportional counter, using a known compound as reference standard. Sakla, Bishara, and Abo-Taleb (269) used oxygen-flask combustion for samples containing cadmium, magnesium, uranium, and zinc. Three mutually confirmatory methods were used on the solution of the metals: ( i ) known volume of 8-hydroxyquinolate in excess was added, the solution filtered, and the precipitate weighed; (ii) the filtrate was treated with KBr and known volume of 0.05N KBr03, acidified KI added, and the liberated iodine titrated with NazSz03 solution; (iii) the precipitate in (i) was dissolved in acid and determined by method ( i i ) . Plank (249) in a collaborative study found that bismuth in pharmaceutical preparations could be extracted and titrated polarographically, the half-wave potential a t -0.1 V us. the SCE being measured. Hoelgye (136) studied the losses by volatilization of ruthenium by heating the dry residues after mineralization of biological samples with Na3P04 and "03. The relationships among many factors were ascertained, and it was found t h a t below 300 "C, losses were small. Duda, Obtemperanskaya, and Dudova (69) proposed thermalneutron activation for the determination of germanium. The 77Be isotope was chosen as being the most suitable. The samples were irradiated in P T F E containers, and the

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activity was measured by scintillation X-ray spectrometry. The same authors (68) measured the activity of the 75mGe in a rapid method by activation with fast neutrons. Borda, Crease, and Legzdins (25) proposed closed-flask combustion for lanthanides in organometallic complexes. Combustion products were absorbed in normal nitric acid, interfering metals removed, and the desired lanthanide element was determined by potentiometric titration with EDTA. Debal (59) digested silicon-containing samples in a micro-bomb with Na202, and the silicon was finally determined colorimetrically with molybdate solution by measuring the extinction a t 400 nm. Terent'ev, et al. (302) proposed a similar technique for organosilicon compounds containing fluorine.

SIMULTANEOUS DETERMINATION OF SEVERAL ELEMENTS The determination of carbon and hydrogen and some other element or elements, especially nitrogen, continues to draw the most interest, with heavy emphasis on automated analysis. For the analysis of carbon, hydrogen, and nitrogen, Ebel (72) described the use of computer programs in conjunction with the Hewlett-Packard gas chromatographic CHN-Analyzer. Reproducibility data over a three-week period were reported. Monar (212) assembled an apparatus consisting of standard units. The sample was burnt in a mixture of ozone and oxygen. The water produced was trapped in a silver spiral a t -70 "C; the carbon dioxide and nitrogen were separated in a copper spiral containing silica gel a t -60 "C and the three components finally determined by thermal-conductivity measurements. Stoffel (291) analyzed more than 300 samples with the Erba CHNO Analyzer, model 1102 and the results were satisfactory. Some improvements were recommended, such as use of Koerbl catalyst, use of boats made of tin and insertion of a 3-cm length of silica tubing into the combustion tube. The same author (292) described the operation of a completely automatic system consisting of a new analyzer, electronic balance, and a small computer. Scroggins (277) used the Perkin-Elmer Model 240 and the Hewlett-Packard F&M Model 185 CHN Analyzer in a collaborative study. Satisfactory results were obtained, but alterations to instrumental parameters were suggested to increase precision. In another collaborative study (278),the modifications to the instrumental parameters were found to be effective. Merz (206) described the design and operation of a n automated system in which nitrogen was determined by a Dumas technique and carbon and hydrogen by a titrimetric procedure after both elements were converted into C02. Oxygen was also converted into C02 and titrated. Results were fed directly into a computer for processing. Smith, Myers, and Shaner (287) used the Perkin-Elmer Elemental Analyzer for petroleum samples with good results. The automated method proved especially useful for samples containing low levels of nitrogen. The method was also evaluated for the oxygen contents by adding known amounts of phenol to the s a m ples, Alicino ( 4 ) recommended a n all-platinum ladle for use in the Perkin-Elmer 240 Elemental Analyzer which, in effect, provided a second combustion. The results were more accurate. Thomas and Robinson (305) described a nickel ladle for use with the aluminum volatile-sample capsule for t h e same instrument. Lapteva, Novikov, Bondarevskaya, and Frangulyan (175) used parallel combustion tubes with programmed heating for simultaneous determinations in a semiautomatic apparatus. Pella and Colombo (243) critically studied a n automatic technique based on dynamic rapid combustion, gas chromatographic separation and thermal conductivity measurement. Improvements were recommended. Hara and Ito (120) determined carbon and nitrogen by decomposing the sample with KIO3-concd. in an atmosphere of hydrogen a t 240 "C. After removal of iodine, t h e C02 and nitrogen were passed to a gas chromatographic column for detection. Kitro and nitroso compounds yielded NO and NO2 which gave broadened chromatographic peaks. Cousin (52) modified the combustion system of the Walisch ultra-micro-analyzer by providing for a longer furnace, thereby prolonging catalyst life and ensuring complete combustion of difficultly decomposed 442R

samples. Fedoseev and Baidulina (82) decomposed the sample in a closed tube containing NiO. An absorption train (anhydrone and 50% K O H solution) was connected to the tube and a vacuum pump. A micro-nitrometer was also present in the system allowing for the simultaneous determination of the carbon, hydrogen, and nitrogen. Many procedures have been proposed for the simultaneous determination of the halogens and some other element and for t h e individual halogens in a mixture. Nuti and Ferrarini (228) determined halogens and phosphorus simultaneously by combustion in a closed-flask, using alkaline NaBH4. The halogens were titrated with 0.01N Hg(C104)2 in t h e presence of diphenylcarbazone as indicator and phosphorus with Ce(N03)2 solution with Eriochrome Black T as indicator. Lisovskii and Smakhtin (181) employed a neutron activation procedure for phosphorus and chlorine. Vladimirova and Fedoseev (323) digested the sample with magnesium in a closed tube. PH3 was liberated in a special apparatus and absorbed on filter paper impregnated with HgC12. The paper was treated with standard iodine solution which was back-titrated with standard sodium thiosulfate solution for t h e phosphorus content. The halogen content of the solution remaining in t h e apparatus was determined by the Volhard method. For the simultaneous determination of sulfur and halogens Osadchii and Fedoseev (232) heated the organic compound with Mg2Si in a special apparatus a t 550-600 "C. H2S was liberated from the residue and absorbed on filter paper soaked in ZnSO4-sodium acetate solution. The zinc sulfide formed was determined iodimetrically . Halogens in the acid solution of the residue were determined by the Volhard method. Avgushevich, Kulikova, Zakharova, and Velichko (9) combusted the sample by the empty tube method and absorbed t h e products in hydrogen peroxide solution. Chlorine was determined by titration with 0.01N Hg(N03)2 with diphenylcarbazone as indicator. so42was titrated with 0.02N Ba( NO& using chlorphosphonazo 111 as indicator. Fadeeva, Borisova and Diakur (77) pyrolyzed samples containing sulfur and fluorine in a closed silica tube in the presence of hexadecane a t 1100-1200 "C to produce H2S and H F and SiF4. The products were a b sorbed in 0.02N cupric acetate solution, and, after filtration the excess copper was determined by titration with 0.02M EDTA with muroxide as indicator. Fluorine was determined by titration with standard T h ( 1L'03)4 solution in the presence of Alizarin red S. Jerie (145) heated samples containing mercury and halogens with alkali-metal carbonate and sodium peroxide. The mercury was distilled off in a special apparatus and weighed. The halogens in the residue were titrated potentiometrically. Obtemperanskaya, Fam, and Karandi (229) decomposed samples containing tin and halogens in a tube containing concd. H2SO4. The decomposition products were absorbed in alkaline peroxide (for bromine or chlorine) or hydrazinium sulfate (for iodine). The halogens were titrated with 0.02N Hg( N03)2 in the presence of diphenylcarbazone. Tin was determined from the weight of the residue in the sample tube. For the determination of the individual halogens, Volodina, Moroz, and Kiseleva (328) heated the sample in a stream of ammonia to produce a binary mixture of ammonium halides. The mixture was titrated potentiometrically with 0.01N AgN03 in a medium of water-acetic acid-acetone. Gaux and Le Henaff (100) employed closed-flask combustion. The absorbing solution was titrated potentiometrically with 0.01M AgN03 in the presence of ethanol0.W H2S04 ( - 6 : l ) . The titration graph shows an inflection for each halide present, but a correction must be made for coprecipitation between C1- and Br- when these are present together. Hassan and Elsayes (123) determined iodine and bromine or chlorine in organic compounds by burning the sample in a n oxygen-filled separating funnel containing acidic sodium nitrite solution. Iodine was extracted with cc14 and determined iodimetrically. The halogen remaining was titrated with standaid H g ( K 0 3 ) solution ~ (diphenylcarbazone as indicator). For the simultaneous determination of carbon, hydrogen, and phosphorus in organic compounds. Bishara and Attia (23) pyrolyzed the sample by t h e empty tube method, placing the sample in a silica capsule. Carbon and hy-

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drogen were determined gravimetrically and oxides of phosphorus were quantitatively retained on the walls of the capsule which allowed a gravimetric determination. Chicherina, Prokop'eva, and Bukina (44) heated carbon, hydrogen, and sulfur-containing samples in a special cell with oxygen a t 1000 "C. The water formed was converted into acetylene by passage over calcium carbide. The resulting mixture of 0 2 , COz, SOz, a n d acetylene was analyzed by gas-liquid chromatography. Fedorova, Nikolaeva, and Kalita (80) decomposed t h e sample in a silica sample tube filled with freshly ignited silica in a silica combus. tion tube. Carbon and hydrogen was determined in the usual way. For organosilicon compounds, the silicon content was determined from the increase in weight of the sample tube. Sheppard and Marlow (280) demonstrated t h a t 5lCr and 14C could b e determined simultaneously by scintillation counting. Horton, Shults, and Meyer (139) in a preliminary report were able to determine nitrogen, sulfur, phosphorus, and carbon in solid ecological samples. The elements were converted into hydrides in a combination pyrolyzer-catalytic hydrogenator (nickel catalyst). The effluent from t h e apparatus was split, one part t o a gas chromatograph responsive t o methane, H2S, and PH3 and another part to a Coulson electrical-conductivity detector responsive to ammonia. Ubik (329) pyrolyzed the sample under hydrogen. With suitable catalysts, the nitrogen a n d oxygen contained in the sample were converted to NZ and CO, respectively, and separated by gas chromatography and detected by a katharometer. Halogens did not interfere, but the method was not suitable for compounds containing sulfur. For t h e same elements, Chumachenko, Khabarova, Egorushkina, and Ivanchikova (47) found t h a t pyrolysis over carbon black for amine or nitro compounds produced (22x2, which was not suitable for determining nitrogen and was, moreover, difficult to separate from CO in the gas chromatographic determination of oxygen. To overcome this interference, a small adsorption chamber filled with active carbon was fitted to t h e inlet of the chromatographic column. For the simultaneous determination of silicon and boron, Terent'ev, Bondarevskaya, and Gradskova (300) fused the sample with sodium peroxide in a n oxygen-filled bomb. T h e melt was dissolved and a n aliquot was treated to produce the methylene blueBF4- complex which was determined colorimetrically. The silicon in a separate aliquot was determined by the molybdosilicate method. Lisovskii and Smakhtin (182) determined sodium and phosphorus in organophosphorus compounds by the technique of fast-neutron activation. The procedures were based on the reactions 23Na(n,p)23Ne,31P(n,2n)30P and 31P(n,a)28A1.

SUBMILLIGRAM SAMPLES The trend toward automation in t h e analysis of organic compounds on t h e milligram scale is even more marked when it comes to the analysis of samples below the milligram level. Reverchon (258) listed the advantages and disadvantages of automation a t the decimilligram level. Various degrees of automation have been achieved and criteria were given for selecting suitable procedures. Some of the apparatus and techniques used were described. Kirsten (160) evaluated the basic methods for sample decomposition including combustion in a stream of oxygen or other gas, combustion by either the cold or hot flask method, combustion in sealed tubes, and wet oxidation. Wojciechowska (340) determined carbon and hydrogen in 1-p1 samples by a gas chromatographic procedure. After combustion, water was converted to acetylene and this was then separated from COZ on a column filled with silica gel impregnated with Octoil S.Roemer, van Osch, and Griepink (260) burnt the sample in a quartz tube and a b sorbed the evolved COz into a titration vessel containing tert-butyl alcohol (1:lO) which was 0.1M in Ba(C104)z a t p H 9.5. The solution was titrated automatically with 0.03M KaOH until t h e p H was restored to 9.5. Patterson (237) described an automated Pregl-Dumas technique for determining carbon, hydrogen, and nitrogen applicable to atmospheric aerosols (samples containing suspended particulate m a t t e r ) . Kirsten (161) used a modified WalischTechnicon analyzer for samples containing carbon, hydrogen. a n d nitrogen. Improvements to the apparatus were

described. T h e necessity for periodically checking scale linearity of weighing balances with long optical scales was stressed. Alicino ( 3 ) determined hydrogen by mixing the sample with Co304 and heating in a stream of COz. The resulting gases were passed over CuO and copper, then over CaH2, and the hydrogen liberated was measured gasometrically. By trapping the water from the initial combustion in silica gel, nitrogen could be determined by the usual gasometric method. T h e water was subsequently released by heating the silica gel, passed over CaH2, and measured as before. Several methods have appeared for the determination of nitrogen a t the submilligram level. Nehring and Hock (224) employed a colorimetric technique for amino-nitrogen. T h e sample was reacted with 1,2-naphthaquinone-4sulfonic acid, unconsumed reagent was reduced with NaBH4, and the extinction of the reaction product measured a t 465 n m . Ubik (320) described a method and a p paratus for the automated determination of nitrogen. The sample was pyrolyzed in a n atmosphere of hydrogen a t 1000-1100 "C and the decomposition products were passed through layers of manganese(I1) oxide and nickel a t 950 "C and t h e nitrogen was determined by means of a katharometer. Morrison (216) presented details of a modified method using Nessler reagent and measuring the extinction a t 420 n m . Several factors had t o be controlled carefully to avoid decreased color development and/or turbidity of the final solution. Warwick (333) compared methods for urea nitrogen in serum, using a commercial product (BUN-Strete), the AutoAnalyzer and Urograph method. Excellent correlations were observed. Krijgsman, Simons, Griepink, and Verduyn (168) digested microliter samples of serum with 35% HC104. After digestion, nitrogen was liberated as ammonia in a special apparatus and titrated both automatically or manually with O.03M HC104 ( p H being maintained a t 5) or by coulometric generation of H' . Bartos and Pesez (11) described a method based on the Schuetze-Unterzaucher procedure for the oxygen content of samples of less than 1 mg. After pyrolysis. the products were passed through a column of carbon a t 1120 "C, interfering elements were removed, and iodine was liberated from 1 2 0 5 by CO. Finally I - was titrated with 0.01M AgNO3 to a potentiometric end point. Vbik, Horacek, and Pechanec (321) developed a n automated method for oxygen in which any CO produced was measured by a katharometer. Any H2S or hydrogen halide formed was removed by absorption on soda asbestos or molecular sieve 5A. For sulfur-containing samples, Carter (38) developed a rapid, inexpensive coulometric technique. After pyrolysis in nitrogen (450 "C) and combustion in oxygen (750 to 800 "C), the products were passed into a Thorn T . E . 110 coulometer, containing 0.1% KI solution in 1% acetic acid and fitted with platinum generator- and indicator-electrodes having a Ag-AgC1 reference electrode in a side tube. Fraisse and Raveau (93) burnt the sample (250-500 pg) to form SO2 which was transferred to a coulometric cell and oxidized to HzS04 and titrated.

TRACE ANALYSIS Because of the large number of papers concerned with trace analyses of organic materials, this section had been divided into two parts: one involving nonmetallic constituents, t h e other with the metallic elements.

Nonmetallic Elements A variety of procedures have been utilized for the trace analysis of sulfur. Debevere and Voets (62) modified the microdiffusion method of Conway applicable to biological fluids. H2S was liberated in a flask fitted with a rod coated with sodium hydroxide solution. A colorimetric finish was employed using dimethylp-phenylenediamine in the presence of FeC13. The extinction was measured a t 670 nm. Jones and Isaac (148) burnt the sample in a crucible with appropriate catalysts and then placed t h e crucible in the induction furnace of a Leco Sulfur Analyzer, where interfering halides were removed by passage of the combustion gases over antimony, before entering the reaction chanber of the titrator. Turunen and Visapaa (318) analyzed the sulfur content of pine needle samples by X-ray fluorescence. A fluorescence

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spectrophotometer with flow-counter and pentaerythritol analyzing crystal was used. The ratio of the net intensities of the sulfur Kz lines for a sample pellet and a n external standard was used. Frigge (95) used X-ray fluorescence analysis for sulfur in coal. Particle size of the sample was important, but this effect can be eliminated by a suitable grinding of the sample. Koch, Schmitz, and Loose (162) employed the X-ray fluorescence technique in solid and liquid fuels, either by a vacuum method or under helium. For the vacuum method, the liquid sample was homogenized, cooled to -10 "C in a n aluminum adapter and then inserted into the spectrometer. Glazov (1IO) determined sulfur in benzene by irradiating the sample with P-radiation. The radiation passing through the sample was recorded by a y-spectrometer, having a n anthracene detector. Thomas and Schweikert (306) irradiated t h e sample with high energy protons, using the reaction 32S(p,n)32C1. The product nuclide emitted high energy positrons which were counted with a Cerenkov detector. Wasserman and Basch (334) modified a method for sulfur on cellulosic fabrics. Instead of combustion for decomposing the s a m ple, digestion in HC1 solution (1:l) was' recommended. Mottershead (218) decomposed biological samples with HN03-HC104 containing N H 4 U 0 3 and. K z C ~ z 0 7 The . resulting S 0 4 2 was determined turbidimetrically in the Technicon AutoAnalyzer. The same instrument was used by Keay, Menage, and Dean (158). Any S042- was reduced to HZS, which was caused to react with Bi(N03)3 solution. The extinction of the colloidal suspension was measured a t 410 nm. Basson and Boehmer (12), after digestion of the sample in HK03-HC104, produced turbidity with a barium chloride solution which was measured in the AutoAnalyzer at 420 nm. Slanina, Vermeer, Agterdenbos, and Griepink (286) hydrogenated sulfur-containing samples to give H2S which was absorbed in alkaline hydroxylamine. The resulting solution was titrated with 0.0002M P b 2 + solution. Gruenert and Toelg (116) also converted sulfur in the sample to H2S by hydrogenation and then determined the S2- either fluorimetrically or by potentiometric titration. Special apparatus was developed for each technique. Greweling, Bache, and Lisk (214) decomposed the sample by closed-flask combustion using a 5-liter flask for -1 gram of plant materials. The sulfur was determined by a n AOAC method, Strukova, Lapshova, Luk'yanov, and Korobova (294) determined sulfur titrimetrically after closed-flask combustion. The solution was titrated with 0.005M Ba(C104)2 with chlorphosphonazo I11 as indicator. Heistand and Blake (129) burnt the sample in a n oxy-hydrogen flame, absorbing the products in KaNOz solution. The sod2- produced was titrated with 0.0025M Pb(C104)z with a 0.5 MA polarizing current through a Pb2+-selective electrode. The potential break a t the end point (determined graphically) was related directly to the sulfur content. Dixon (64) modified the Dohrmann microcoulometric method to ensure more complete combustion of lubricating oil samples. The products of combustion were carried in a stream of helium to a cell in which SO2 was titrated with electrogenerated iodine. For sulfur in coke-oven gas, Plankert (250) freed the gaseous sample of inorganic sulfur and then converted organic sulfur to H2S by hydrcgenation. The H2S formed was determined by measuring the length of the colored zone in a commercially available gas-indicator tube directly calibrated in ppm of H2S. Malissa, Kellner, and Pel1 (198) decomposed mineral-oil products (-10-ml sample) in a Wickbold apparatus and absorbed the SO2 in 10% H202 solution. A known volume of barium acetate solution was added and the conductivity was measured with a high frequency titrator. The sulfur content was read from a calibration graph. For sulfur in liquid hydrocarbons, reduction with Raney nickel was recommended by Mackinger (193). H2S was liberated and absorbed in a tube filled with silica gel impregnated with lead acetate and acetic acid, the content of sulfur being determined from the degree of blackening. Grundon and Asher ( I 17) used closed-flask combustion for sulfur-35 in plant material. A %liter flask with a rubber balloon fitted to a side arm was employed. The 35s activity was determined by liquid scintillation counting a n aliquot of the absorbing solution, adjusted to a 1:l:Z ratio of toluene to Triton X-100 to water with 0.25% of 2,5-diphenyloxazole ~

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ANALYTICAL CHEMISTRY, VOL

added as fluor. Bates and Boyd (13) determined sulfur-35 in milk by mixing a portion of the barium sulfate precipitate, obtained from the determination of total sulfur, with NE-221 gel scintillant and counting in a liquid scintillation counter. Mauss (201) described a combustion apparatus for the determination of trace amounts of chlorine and sulfur. Krijgsman, de Groot, van Bennekom, and Griepink (167) developed an automated method for trace amounts of chlorine in which the combustion gases from the sample were subjected to coulometry. The interference caused by nitrogen oxides was overcome with sulfamic acid. Svajgl (295) used a n automatic titrator for the coulometric determination of chlorine. The C1- solution was titrated with electrogenerated Ag+ using amperometric indication for the end point. Krijgsman, van Bennekom, and Griepink (166) gave details of a simple coulometer suitable for trace amounts of chlorine (or acid and base). The electrogenerated titrant was Ag+ or OH-. Tong e t al. (323) analyzed halogenated herbicide residues in soil for bromine or fluorine by spark-source mass spectrometry. The residues from the soil were mixed with graphite and excited between graphite electrodes, and the spectra were recorded. Petri and Erdtmann (244) irradiated a n iodinecontaining sample and standard in a thermal-neutron flux. The silica ampoules containing the test compounds were counted for 1281 formed from the 1 2 q . Measurements were made a t 443 keV with a Ge(Li) detector and a 4000channel analyzer. Peisach, Comar, and Kellershohn (240) analyzed biological samples containing trace amounts of bromine by irradiation and measurement of the 11.9-keV K X-rays (emitted from 82mBr) by means of a NaI crystal covered with a beryllium window. Heurtebise (132) developed an automated system for the rapid determination of traces of iodine in biological fluids. The sample was irradiated, the I - separated from other anions by ion exchange, and then counted in a n automated counting system in which the 1281 was determined with a NaI(T1) crystal connected to a multi-channel analyzer. Mantel (199) determined iodine in urine by an improved method. After dry ashing, the catalytic reaction between Co4+ and As3+ was stopped by the addition of Fez+, and the Fe3+ formed by oxidation by the remaining Ce4+ were determined as the SCN- complex which was measured at 460 nm. For fluorine, Kakabadse e t al. (155) combusted the biological materials and absorbed the gases in water or dilute alkali. Fluorine was determined spectrophotometrically with Ce3+-alizarin complexan and with a F--semitive electrode. M a and Gwirtsman (190) determined ppm amounts of fluorine in tea by fixing the fluorine with calcium oxide during the destruction or organic matter. Fluorine was then converted to soluble fluoride by fusion with sodium hydroxide, fluorosilisic acid was separated by steam distillation and the fluorine determined titrimetrically. Pochinok (251) analyzed plant material for traces of amino-nitrogen with a modified ninhydrin reagent (solution of ninhydrin in ethanediol-butanol-propanol). A joint TAPPI-ASTM paper analysis committee (147) recommended a modified Kjeldahl procedure sensitive to 0.01% nitrogen. Thuerauf and Assenmacher (309) extended a previously described method for nitrogen to the microgram range. The sample was decomposed in oxygen, COZ and water were absorbed in potassium hydroxide solution, and the nitrogen was carried by a stream of helium into a thermistor cell. Wernberg, Lamm, and Nielsen (338) converted nitrogen in biological materials to nitrogen gas with NaBrO for the analysis of traces of nitrogen-15 which was determined by gas-solid chromatography on a copper column with Porapak Q operated a t 45 "C with nitrogen as carrier gas and a gas-density-balance detector. Fabbro e t al (76) modified a micro-coulometric method for nitrogen to permit the determination of 0.1 ppm to 1.0% with precisions of izO.03 ppm and &0.00270, respectively. Croll (53) made improvements to a method for traces of organic carbon in water. The sample (40 ml per hour) was passed through a combustion tube packed with CuO (900 "C) and the C02 liberated was hydrogenated a t 450 "C and the resulting products, after removal of water and "3, were passed to a flame ionization detector. The blank value was reduced to 0.1 mg per liter. Colombo (49) developed a n apparatus for trace amounts of oxygen applicable to

46, N O . 5 , A P R I L 1974

dures for obtaining metallic mercury for atomic absorpeither a 0.5-mg to 30-mg sample without modification to tion analysis ( i ) digestion with HNOS in a sealed tube, the apparatus. The method was based on catalytic pyrolyelectrolysis of the resulting solution and vaporization of sis and reduction with hydrogen, followed by measurethe mercury on the platinum electrode for analysis, (ii) ment of the water formed with a commercial Keidel elecdecomposition with H2S04-HN03 in the presence of VzOs trolytic hygrometer. and reduction of Hgz+ with SnClz to produce mercury Kaczmarczyk, Messer, and Peirce (151) developed a which was vaporized and subjected to atomic absorption rapid method for trace amounts of boron in biological maat 253.7 nm. Thomas, Hagstrom, and Kuchar (307) burnt terials. The method, based on reaction with 1,l'-diant h e sample (50-150 mg fish tissue) in a stream of oxygen thrimide, allowed results to be obtained within 3 hours. at 900 "C, then passed t h e combustion products over CuO Monnier, Menzinger, and Marcanlonatos (213) decomat 850 "C. Interfering substances were removed and merposed samples of blood with Ca(OH)2 a t 550 "C in a silica cury in the air stream was determined a t 253.7 nm. Saha tube in a fluorimetric method for trace amounts of boron. and Lee (268) recommended t h e extraction of fatty mateThe residue, after oxidation with 30% H202 was treated rials with chloroform before extraction of Hg2+ from diflith 4'-chloro-2-hydroxy-4-methoxybenzophenoneand the gested fish samples with dithizone solution in a flameless fluorescence of t h e solution was measured at 490 nm (exatomic-absorption technique for mercury. Cava!laro and citation a t 365 n m ) . Moore (215) determined boron in Elli (41) digested food samples with acidic KMn04, repharmaceuticals by a modification of a previously deduced t h e HgZ+ with SnC12, and after stripping the merscribed method. After alkali-fusion of the sample, the rescury from the solution with a stream of air which was idue was now dissolved in a solution of aniline in acetic passed into a cell, measured the atomic absorption a t acid and sulfuric acid, obviating the addition of a critical 253.7 n m . Lindstedt and Skare (180) developed a n appavolume of water and preventing the interference of NOSratus for a rapid automated technique in which the samwhen curcumin reagent was added for color development. ple solution (1 ml urine) was digested overnight with Pau, Pickett, and Koirtyohann (238) proposed a method KMn04-H2S04, then heated with SnC12 to produce merfor boron in plants which involved ashing of the sample, cury metal and then mercury vapor was liberated by a extraction of the dissolved ash with 10% 2-ethylhexanestream of nitrogen and passed into a cell of Plexiglas with 1,3-diol solution in chloroform. The extract was burnt in a nitrous oxide-hydrogen flame and the boron content dequartz windows for flameless atomic absorption. Skare termined by emission spectroscopy (absorption a t either (284) extended the above method for mercury by using a 518.2 or 547.6 n m ) . Drewes (67) determined phosphorus in KMn04 digestion procedure for urine and digestion with serum and urine by treating t h e sample directly with a HN03-HC104 for blood. Hauser, Holenstein, and Nusscolorimetric reagent consisting of 4-methylaminophenol baumer (124) developed a rapid extraction process for sulfate and Na2S205 in water and ( N H ~ ) ~ M o ~ O Z ~in. ~ H mercury ZO residues in fish. The sample was digested with alkaline K M n 0 4 , acidified, and the resulting solution concd HzSO4 and water. Fawcett, Green, and Shaw (79) used for the direct determination of mercury by atomic analyzed pollen samples for their phosphorus content by absorption spectrometry. Mesman, Smith, and Pierce using a neutron-activation technique. The samples were (209) extracted mercury from urine with isobutyl methyl irradiated and, after storage in polyethylene capsules for 5 ketone in the presence of ammonium pyrrolidine-l-carboweeks, were counted for the @ activity of 32Pwith a n enddithioate. An aliquot was cransferred to a tantalum boat, window Geiger-Mueller tube. Interferences from other the solvent evaporated, and t h e mercury determined by long-lived weak emitting nuclides were overcome by using atomic absorption spectrophotometry. Schaller, Strasser. aluminum absorbers between the samples and t h e counter Woitowitz, a n d Szadkowski (272) reported results of the window. Toralballa, Spielholtz, and Steinberg 1315) deteranalysis of mercury in urine from men suffering from ocmined phosphorus in detergents by atomic-absorption cupational exposure to the element. The technique inspectroscopy. After decomposition of t h e sample, the volved concentrating the mercury on copper wire by elecmethod of additions was used. The absorption readings in trolysis, followed by analysis using flameless atomic a n acetylene-nitrous oxide flame were plotted against added concentration of phosphorus and the phosphorus absorption. Thorpe (308) recommended a simple method content of t h e sample was measured graphically. Pottin which the sample was digested with H2SOd-KMn04, kamp and Umland (253) employed a direct polarographic reduced with SnC12, and a 10-ml sample of the headspace procedure for traces of phosphorus a n d silicon in organic vapor, drawn by syringe, transferred to a spectrophotomesolvents. The phosphorus or silicon was converted into its ter cell for atomic absorption. Munns and Holland (220) dodecamolybdo-acids, which were distributed between reported results of a collaborative study for the determiwater and butyl acetate and then analyzed in a Metrohmnation of mercury in fish. The over-all recovery of 0.3-0.8 Polarecord instrument with ethanolic lithium chloride as ppm was 84%. The method involved digestion, reduction electrolyte. Kadner and Biesold (152) fused silicon-conwith SnC12, and circulation of the mercury vapor in a taining samples with K O H and, after treatment of the closed system and measurement a t 253.7 nm. Rains and melt, precipitated the silicon with sodium fluoride and Menis (255) proposed modifications to a previously depotassium chloride. The precipitate was collected, scribed method for traces of mercury. using standard refwashed, and hydrolyzed to H F which was titrated with erence materials as samples. The main modifications in0.05.V I i a O H . volved controlled heating during digestion, reduction with SnC12 in the absence of hydroxylammonium chloride Metallic Elements (found to be a constant source of contamination), and the use of argon as a sweep gas. Gonzalez and Ross ( 1 2 1 ) couThe detection and determination of the heavy pled gas-liquid chromatography with flameless atomic abmetals, especially in foods, dominates this secsorption for traces of alkylmercury compounds in fish tistion on the analysis of trace amounts of metallic elements sue. The sample was extracted with benzene and an aliin organic substances. Mercury in particular has received quot of the separated and dried benzene layer was particular attention because of the many environmental subjected to GLC. The mercury-containing compounds problems associated with the levels of mercury in natural were burnt in a n oxy-hydrogen flame and the gases a n a substances. Flameless atomic-absorption spectrophotomelyzed for mercury by passage into a n atomic absorption try has been used by many researchers. Magos and Clarkspectrophotometer. Preferably, the gases from the chroson (195) modified a previously described method by matograph were burnt in oxygen in a furnace a t 780 "C using a cell with a longer p a t h length and purifying the and the products were passed directly into a Coleman reagents to obtain lower blank values. Malaiyandi and MAS-50 flameless mercury analyzer. Barrette (197) digested flour samples with H2S04-HKO3 in the presence of V z 0 5 . The final determination involved A number of authors have reported on the use of neureduction to metallic mercury and analysis by atomic-abtron activation analysis for trace amounts of mercury. sorption spectrophotometry. Fabbrini, Modi, Signorelli, Weaver (335) gave optimum experimental nuclear analysis and Simiani (75) reported results for total mercury and parameters for mercury and selenium in coal. Pillay, methylmercury in canned tuna. For total mercury, atomic Thomas, Sondel, and Hyche (217) irradiated samples toabsorption was used; for methylmercury, conversion to a gether with mercury standards. The sample was wet mercaptide complex, followed by gas-liquid chromatograashed along with a known amount of mercury; the mercuphy was recommended. Cumont ( 5 5 ) proposed two procery was precipitated as the sulfide, deposited on gold foil ANALYTICAL CHEMISTRY

VOL

46, N O 5. A P R I L 1974

445R

by electrolysis and weighed. The y - and X-ray emissions from 197Hg and Ig7mHg were counted. Recoveries were in the range of 75-90%. Rottschafer, Jones, and Mark (266) irradiated the sample and after 2 or 3 days digested the sample with HN03-HzS04 containing a known amount of HgZ+ and passed the digest through the resin Dowex 2-X8 ( H + ) .After washing, the resin was removed and counted directly (Ig7Hg;77.3 keV). Filby, Davis, Shah, and Haller (86) treated t h e sample in polyethylene vials with a thermal-neutron flux for 8-10 hours. Samples and standards were left for 3-6 weeks and then counted with a Ge(Li) detector under constant-geometry conditions for 2 to 10 hours, the @-ray spectrum being recorded and processed on a computer for evaluation of the 203Hg peak at 279 keV. There were no significant interferences and the problem of mercury volatilization was eliminated. Ruf and Rohde (267),after irradiation and digestion of the sample, distilled the mercury in the presence of glycine-HC104 causing the volatilization of HgClz which was collected in water. Mercury from this solution was deposited on weighed gold foil by electrolysis. Finally the y-activity of Ig7Hg was measured a t 77 keV with a NaI(T1) crystal and a multi-channel analyzer. A number of other procedures have also been reported for trace amounts of mercury. Henrioul, Henrioul, and Henrioul (231) considered spectrophotometric, atomicabsorption and nuclear-reaction methods and preferred the first. The sample was extracted with Hz02 in HzS04 medium, followed by extraction of the mercury into CHCl3 as the dithizonate. Because of the instability of the mercury complex, the unconsumed dithizone was determined a t 610 nm. Legatowa (177) determined traces of mercury in beer and its raw materials by a titrimetric dithizone method and by a spectrophotometric dithizone method. No significant differences between the two methods were found. Uthe, Solomon, and Grift (322) analyzed fish samples for methylmercury by extraction into toluene as methylmercuric bromide, partitioning into aqueous ~reextracting into benzene ethanol as the S ~ 0 3 complex, and gas-liquid chromatography on a glass column packed with 770 Carbowax 20M on Chromosorb W, operated a t 170 "C, with nitrogen as carrier gas and electron-capture detection. Kamps and McMahon (156) proposed a similar procedure for methylmercury in fish (the Westoo procedure). Rohm, Sipper, and Purdy (262) utilized a procedure in which the C Y released by the Hg2+-catalyzed replacement reaction between Fe(CN)e4- and 1,lO-phenanthroline at 60" and p H 3 were titrated coulometrically a t p H 9.2 with electrolytically generated iodine. The calibration graph was rectilinear for up to 1.5 ng of mercury. For mercury in crude oils, Hinkle (134) employed closedflask combustion, followed by treatment with aqueous chlorine, the mercury being absorbed onto a silver-gauze screen in the flask. The screen was placed in the induction furnace of' a mercury-vapor absorption detector. The mercury content was determined by reference to a calibration graph. Corvi (51) ashed the sample and fixed the volatilized mercury in a n acid solution of KMr-104. The Hg2* was reduced with hydroxylammonium chloride, extracted at p H 1 as the dithizone complex. The complex was purified by thin layer chromatography and the Hgz+dithizone band was removed, the complex extracted and determined spectrophotometrically a t 483 nm by reference to a calibration graph. Magos (194) reduced samples containing organic and inorganic mercury with SnC12-CdC12 solution and determined the mercury produced in a mercury-vapor concentration meter. The inorganic mercury content was determined by reduction with SnClz alone as the release of organic mercury (from methylmercury) was slow. Anderson, Evans, Murphy, and White ( 5 ) burnt the sample in a stream of air and collected the mercury in a gold-impregnated fritted glass disk and the mercury was determined by placing the disk in a portable atomic-absorption spectrophotometer. For the determination of trace amounts of lead, the technique of atomic-absorption spectrometry has wide applicability. Hoover (138) conducted a collaborative study of from 5 to 20 ppm of lead in food products using a previously described method involving atomic-absorption. Good recoveries were reported. Bratzel and Chakrabarti (271 determined lead in petroleum products using a Var446R

ian Techtron model 61 carbon-rod atomizer, with a R-106 response phototube; the slit-width was 0.1 mm, corresponding to a spectral band-pass of 0.33 nm. The sample was dried, ashed, and atomized sequentially by passage of a n electric current through the carbon rod. Absorption was a t the 217- and 283.31-nm lead lines. Mack and Berg (192) digested food materials with H2S04-HN03-aq. H202 and extracted into isobutyl methyl ketone the complex of lead with ammonium pyrrolidine-1-carbodithioate. The lead was determined in an atomic-absorption spectrophotometer with a n air-acetylene flame at 283.3 nm. The calibration graph was rectilinear in t h e range of 1-20 kg of lead. Campbell and Palmer (33) extracted lead from petroleum products with iodine chloride reagent, then formed a n iodide complex which was extracted into isobutyl methyl ketone. The lead content of the extract was determined by atomic absorption spectrophotometry a t 283.3 nm using a n air-acetylene flame. For the determination of trace amounts of lead in fish, Gajan and Larry (97) published procedures involving ashing the sample and determining the lead in t h e dissolved residue by polarographic and spectrometric procedures. The same a u thors (98) subjected the above procedures to collaborative study. Further study of the spectrophotometric method was recommended because of the biased results obtained at low levels of lead. Zuber (345) used atomic-absorption spectrometry (air-acetylene flame, 283 nm) for the lead content of plant materials. The sample was first ashed and then the residue dissolved in nitric acid and diluted with water. Yeager, Cholak, and Henderson (342) ashed the sample. The ash was dissolved in water containing ammonium citrate. T o this solution was added KCK to suppress interference by iron, zinc, and copper, followed by ammonium pyrolidine-1-carbodithioate as chelating agent and isobutyl methyl ketone as extractant. The organic layer was analyzed for lead by atomic-absorption a t 283.3 nm. Doellefeld (66) gave procedures for the lead content of blood and urine in which the final determination involved atomizing the sample a t 2300 "C in a flow of argon and measurement of the absorption at 283.3 nm. Fletcher (87) analyzed plant materials, after ashing and solution of the residue, in an air-acetylene flame with measurement at 217 n m with a hollow-cathode lead lamp ss source. Pagenkopf, Neuman, and Woodriff (233) employed furnace atomic absorption for lead in fish. The fish tissue was digested and the final solution in graphite cups was heated to 1850 "C in the furnace. Recoveries ranged from 95-102%. Mutsaars and Van Steen (221) combined a gas chromatographic procedure with a flame-photometric method for alkyl lead components in petroleum products. The spectrophotometer with oxy-hydrogen flame and the photomultiplier unit was operated a t 405.8 nm. Hauser, Hinners, and Kent (1.25) determined traces of lead and cadmium in whole blood by ashing in a tantalum boat which was then inserted into the air-acetylene flame of the atomic-absorption spectrometer. Calibrations were made by applying a standard solution of cadmium or lead to the cooled sample ash in the same boat and reinserting the boat into t h e flame. A variety of other procedures have been used to determine trace amounts of lead in organic materials. Dutilh and Das (71) evaporated milk samples, pressed the residue into pellets which were irradiated in poly(viny1 chloride) vials with y-photons, and isolated the lead as the chromate. The precipitate was then counted. Hislop and Williams (135) irradiated the samples and standards with 35-40 MeV electrons and then applied a radiochemical separation. Down to 0.1 pg of lead can be detected. Kaumann and Zimmerschied (223) determined lead-210 by irradiating the sample, treating with aq. H202-Fe2+, plating the daughter-nuclide (zlOBi) onto nickel and then counting the resulting a-activity. Webber (336) compared ignition treatments for determining trace amounts of lead in plant tissues. Results for lead after wet ashing with HN03-HC104 or one dry ashing a t 430 "C followed by fusion with Na2CO3 were in good agreement. Sinko and Gromiscek (283) were able to determine lead and several other elements simultaneously in blood serum by anodicstripping voltametry. A solution of the residue after wetashing was electrolyzed and the current-voltage curves were recorded a t various potentials. Analysis of these

A N A L Y T I C A L C H E M I S T R Y , V O L . 46, N O . 5 , APRIL 1974

adzka a n d Sokolowska (344) determined traces of zinc in curves yielded not only the lead content, but t h a t of cadbiological material by polarographic and colorimetric mium, copper, thallium, bismuth, and zinc. methods, the latter being preferred. Iron, Cobalt, and Zinc. Davies, Bush, and Motzok (57) analyzed diets containing 7-30 ppm of iron by either the Selenium, Copper, and Tin. Morss, Ralston, and 01cott (217) used a procedure based on neutron-activation sulfonated bathophenanthroline colorimetric or atomicanalysis for trace amounts of selenium in lipoprotein fracabsorption method. Values obtained by the latter method tions of human serum. Rook (263) described a rapid, were significantly more variable. Zak, Baginski, Epstein, quantitative separation procedure after irradiation of bioand Weiner (343) developed a new color reagent for serum logical materials. The sample was burnt in a crucible in iron. T h e test solution was treated with 4,4',4"-triphenyloxygen a t 875-1000 "C, and the volatile products were 2,2':6',2"-terpyridinesulfonate (Terosite sulfonate) and condensed a t -196 "C, dissolved in dilute nitric acid, and the extinction was measured a t 583 nm. Gundersen and counted with a Ge(Li) detector, the 265-keV y-radiation Steinnes (118) proposed isotopic-dilution analysis fqr tracof 75Se being used. Maziere, Comar, and Kellershohn es of iron in biological materials. T o the sample was (202) determined traces of selenium in plasma or serum added 59Fe tracer solution and after a series of extractions by irradiating the sample, storage for 2-6 days to allow including passage through an ion-exchange column, the parasitic radio-isotopes to decay, wet digestion along with eluate was counted with a scintillation counter. The aca known weight of carrier selenium, separation from intertivities of a reagent blank and of a similar final volume of fering metals by ion-exchange, extraction with diethyldi59Fe tracer solution were also needed. Bernegger, Keller, thiocarbamate, and measurement of the activity of the exand Wenger (17) used a n automated method for the suctract by y-spectrometry of the 75Se peak a t 410 keV, by cessive determination of iron a n d copper in serum based means of a NaI detector. Japenga, Das, Hoede, and on the formation of a complex between Fe3+ and 7bromo- 1,3-dihydro-l-(3-dimethylarninopropyl)-5-(2-pyri-Zonderhuis (144) developed a method for selenium in blood by neutron-activation which was based on precipidyl)2H-1,4-benzodiazepin-2-one dihydrochloride and, after tation of elementary selenium and counting of Pathe change of reagents, the determination of copper with triarche (236) digested samples of urine with "Osoxalyldihydrazide-acetaldehyde reagent. Toma and Crisan (312) used atomic-absorption spectrophotometry for trace HzSOr-aq. HzOz and distilled off selenium compounds in the presence of bromine and HBr. The selenium was preamounts of iron, zinc, sodium, and magnesium in acrylonitrite-butadiene-styrene copolymer. The metals were decipitated with hydrazine sulfate, converted to Se4+ and termined respectively at 248.3, 213.9, 589.0, and 285.2 nm treated with acidified KI to produce iodine. Excess sodiu m thiosulfate was added and the excess was titrated couwith air-acetylene or air-propane flames. Jago, Wilson, and Lee (143) digested cobalt-containing lometrically with electrogenerated iodine. Alder and West ( 2 ) determined copper and silver in lusamples (plant and animal tissues) with a mixture of "03, HC101, and HzSO4. 1-Nitroso-2-naphthol was bricating oils by atomic-absorption and fluorescence specadded t o form a complex with cobalt which was extracted troscopy. The metals were vaporized a t 2500-2700 "C; into chloroform. The chloroform was evaporated, the resicopper was determined a t 324.7 nm and silver a t 328.1 nm. Calme, Gerhard, and Kraeminger (31) used a coloridue dissolved in ethyl methyl ketone, and the cobalt demetric method for traces of copper in the serum from the termined by atomic absorption a t 240.7 nm in a n air-acethuman eye. T h e reaction of KI with Cu2+ was used to libylene flame. The useful range of the method was 0.2-2 ppm cobalt in the dry sample. Gelman (106) ashed the erate iodine, which then formed a pink complex with poly(viny1 alcohol). The complex was determined at 490 sample, formed a cobalt complex with ammonium pyrrolidine-1-carbodithioate, extracted the complex with isobunm. Vrignaud, Vrignaud, and Blankquet (331) proposed a tyl methyl ketone, and determined cobalt by atomic abradioisotopic dilution method for copper in human serum. sorption spectrophotometry. The ashing was the most Known amounts of 'j4Cu were added to the test solution; after extraction with dithizone in chloroform, the activity critical part of the analysis as there was a risk of cobalt of the organic layer was counted. Farhan and Makhani being retained on silica or porcelain ware. Simmons (282) gave analytical results and standard deviations for the (78) used the technique of emission-spectrography for the analysis of plant materials for cobalt by atomic-absorption direct determination of traces of copper in biological maspectrophotometry. Dewey and Marston (63) employed a terials. The 324.75-nm line was used and the analysis was spectrophotometric procedure for cobalt in plant materieffected by the standard-addition method. Roschnik (264) als. The sample was digested, extracted with l-nitroso-2determined trace amounts of copper in butter by atomicnaphthol, and color development was with nitroso R salt. absorption spectroscopy, using the 325-nm line. Byrne (30) irradiated biological samples containing The extinction was measured a t 480 nm. Beers law was trace amounts of tin and, after ashing, extracted the disobeyed for u p to 20 pg of cobalt, Fez+ interfered but this solved residue with toluene. The extract was treated with could be avoided by masking with &Pod. Pelekis, Pele1.5M HZSOI-lM KI to remove arsenic and antimony. Tin kis, Taure, Kizane, and Rusteika (241) irradiated blood was re-extracted and the activity of the extract was measamples together with a cobalt standard. After 100 days, sured for its y-ray activity with a well-type NaI(T1) crysthe y-ray peak for 'j0Co was measured a t 1.33 MeV by tal and a 256-channel analyzer. Bowen (26) also proposed means of a ?-ray spectrometer with a coaxial Ge(Li) deneutron-activation analysis for tin in biological samples. tector linked to a 512-channel analyzer. conditions were The sample was irradiated, wet-ashed with carrier tin soalso given for determining the 'j0Co activity after 10-15 lution and the metal separated from interfering elements. days. Moody and Taylor (214) determined zinc in pharmaceuThe tin was precipitated as SnSz and the a-activity of the tical preparations. The test solution (containing -0.5 IZ1Sn in the precipitate counted with a scintillation counp p m ) was aspirated into a n air-acetylene flame and the ter with a thin crystal of anthracene as detector. Lowry and Tinsley (183) determined traces of tin salts in fats by absorption a t 213.9 nm was compared with t h a t of a blank and standard solution. Kurz, Roach, and Eyring (172) treating the heated sample with catechol violet in ethyl used an atomic-absorption spectrophotometer fitted with acetate. The extinction a t 560 nm was measured. Reproducibility was satisfactory within the range of 5 to 20 j ~ of a pre-mix, laminar-flow burner system and a n air acetyg lene burner for zinc a n d copper in serum (213.9- and tin but the calibration graph showed a change of slope a t 324.8-nm lines, respectively). Holding and Matthews (137) -25 pg. Havranek, Bumbalova, a n d Kapinsinska (127) recommended a mixed solvent system for the determinadeveloped a n X-ray fluorescence technique for tin in polytion of zinc a n d calcium in petroleum products by atomic(vinyl chloride). The tin K radiation (25.2 keV) excited by absorption spectrophotometry. A fuel-lean air-acetylene low-energy y-radiation from a 247Am source was measured flame a n d absorption at 213.9 nm for zinc and 422.7 n m by means of a NaI(T1) crystal, a single beam y-spectromefor calcium, was used. Vrignaud, Vrignaud, and Blanquet ter being used for evaluation. (332) used a radioisotope dilution method for zinc in Manganese, Strontium, Chromium, Gold, and Arseserum. To a prepared solution was added 'j5Zn tracer and nic. Bek, Janouskova, and Moldan (16) determined manthe zinc was extracted with diethyldithiocarbamate and ganese a n d strontium directly in serum by atomic-absorpdithizone into chloroform. The activity of this solution tion using the Perkin-Elmer HGA-70 graphite cell. The was measured by scintillation counting. A blank and a sosample (20 ml) was burnt in the cell and the atomic ablution of known zinc content were treated similarly. Zawsorption was measured a t 279.48 and 460.73 nm for manA N A L Y T I C A L C H E M I S T R Y , V O L . 46, NO. 5, A P R I L 1974

* 447R

ganese and strontium, respectively. Angelieva (6) used a spectrographic method for manganese in urine. The sample was evaporated, ashed, the residue mixed with H2Si03 and carbon powder, and portions of the mixture were placed in the cavity of each carbon electrode of the spectrograph, and manganese was determined with excitation a t 12 A. Maillard, Maziere, and Comar (196) irradiated rat plasma samples and determined strontium by neutron activation after separation of t h e strontium from interfering elements. Das and coworkers (56) used neutron activation for the determination of trace amounts of chromium in milk powder. The sample was irradiated and K2Cr04 was added as carrier. The extraction of chromium as peroxochromic acid and its re-extraction with aq. NaOH was carried out. The Cr04'- was then precipitated and the activity of W r at the 0.32-MeV photopeak was measured. Savory, Glenn, and Ahlstrom (271) utilized gas chromatography to determine chromium in serum. The chromium was isolated as the trifluoroacetylacetonate and dissolved in hexane. An aliquot of this extract was injected into t h e chromatograph which consisted of a glass column packed with 5% of SE-52 on Gas-Chrom Q and operated a t 180 "C with argon-methane (19:,1) as a carrier gas and electron-capture detection. Davis and Grossman (58) digested chromium-containing samples with HN03HC104-H2S04 and extracted the digest with 10% tributyl phosphate in isobutyl methyl ketone. The extract was aspirated into a fuel-rich air-acetylene flame for atomicabsorption measurement a t 357.9 nm. Cary and Allaway (39) described a method for chromium in biological materials based on atomic-absorption spectrophotometry. The chromium was extracted from the residue after wet oxidation with ammonium pyrrolidine-1 -carbodithioate and acetylacetone. The chloroform extract with the acetylacetone was used for the atomic absorption determination. Schiller and coworkers (274) determined gold in plant material by neutron activation. The sample was ashed, irradiated together with gold standards, and after 6 days, the complete y-spectrum up to 2 MeV was recorded with a Ge(Li) detector inside a Compton shield containing liquid scintillator; the gold content was calculated from the Ig8Au peak a t 412 keV. Dunckley (70) used atomic-absorption spactroscopy for gold in serum. Measurements were made at 242.8 nm, a n air-acetylene 10-cm slot burner being used. The serum was diluted and compared to standard gold solutions containing human albumin due to the enhancement effect of the serum protein. For trace amounts of arsenic in urine, Jovanovic and coworkers (150) precipitated t h e arsenic with uranyl acetate solution. The precipitate was dissolved in HC1 and treated with KI-SnC12 solution and granular zinc to evolve AsH3 which was absorbed on filter paper impregnated with HgC12. The stain produced on the paper was compared to standards, or the paper was treated with 0.005N iodine, ( N H ~ ) ~ M o ~ O ~ and . ~ Hhydrazine ~O, sulfate and the extinction of the molybdenum blue produced was measured a t 850 nm and compared to a calibration graph. Balazs, Pole, and Masarei (10) determined gold in body fluids by atomic-absorption spectroscopy. The fluid was mixed with KMn04-HC1, heated to 100 "C, extracted with isobutyl methyl ketone, and the extract aspirated into a n air-acetylene flame, with atomic-absorption measurement a t 242.8 nm. Lunde (184) analyzed the lipid phase of marine algae for arsenic. The lipid in hexane was irradiated together with arsenic standards and measured by y-ray spectrometry of 76As. Schwedt and Ruessel (276) employed closed-flask combustion for the determination of arsenic in plant material. The absorbing solution was treated with aq. KI and aq. N a H S 0 3 and extracted with diethyldithiocarbamate solution in dichloromethane. The extract was reacted with diphenyl-magnesium solution in ethyl ether. After evaporation, the residue was treated with mercaptoacetic acid solution and subjected to gasliquid chromatography on a column packed with 5% of terephthalic acid-treated Carbowax 20M on Gas-Chrom Q and operated a t 220 "C with nitrogen, helium, or argon as carrier gas and flame ionization, thermal conductivity, or argon ionization detection, respectively. Aluminum, Uranium, Cadmium, a n d Lithium. Gilmore and Goodwin (108) avoided interference from 31P(n,2)28A1 in the neutron-activation analysis for alumi448R

num in bone samples. The aluminum in the solution of the sample was retained on a n ion-exchange column while Po43- was eluted. The column was irradiated and the activity of the aluminum was counted using the crystal of a Ge(Li) detector in conjunction with a 512-channel analyzer. Krishnan, Gillespie, and Crapper (269) proposed atomic-absorption spectrophotometry for aluminum in biological material. The tissue was digested, the resulting solution made u p to >500 pg Na+ per ml and the aluminum content measured a t 396.1 nm. Piskorska-Chlebowska and Geisler (248) described two procedures for determining natural uranium in urine. The first was a rapid method involving direct fluorimetry of the ashed urine and the second, a lengthier one in which the uranium was extracted into ethyl acetate, before measurement of the fluorescence. A method for uranium-235 also involved extraction into ethyl acetate, the separated 235U then being determined by measurement of the a - a c tivity. Becker and LaFleur (15) proposed neutron activation and a rapid radiochemical separation procedure for uranium in biological materials. The sample was decomposed by wet-ashing after irradiation and the uranium extracted with bis(2-ethylhexy1)hydrogen phosphate in light petroleum, the activity was measured from the 239U 75keV y-ray. Lener and Bibr (178) determined traces of cadmium in biological materials by atomic-absorption spectrophotometry. Either t h e cadmium was determined directly after wet-ashing of the sample or after extraction of the digest with dithizone in chloroform. Rost and coworkers (265) published a procedure for the determination of lithium ions in serum based on a flame-photometric method. Molybdenum, Vanadium, Beryllium, a n d Antimony. Ssekaalo (289) determined molybdenum in plant material by a spectrophotometric procedure. The sample was wetashed, extracted with toluene-3,4-dithiol solution, and the extinction of the extract was measured a t 682 nm. The results were referred to a calibration graph. Welch and Allaway (337) digested vanadium-containing samples with HN03-HC104 and extracted the metal with 8-hydroxyquinoline in chloroform. The vanadium was then extracted into aq. NH4N03 buffer solution of pH 9.4 and determined by its catalytic effect on the rate of oxidation of gallic acid by a solution of (NH4)2SzOg in phosphoric acid. Christian (45) proposed a method for traces of vanadium in blood which involved the vanadium-catalyzed oxidation of 4-hydrazinobenzene sulfonic acid by NaC103 to give a diazonium salt which was coupled with 1-naphthylamine. The extinction of the reaction product was measured a t 530 nm and the results were referred to a calibration graph. Arroyo and Brune (7) used neutron-activation for vanadium in petroleum products. The sample was irradiated and t h e 1.44-MeV y-ray of 52V was measured and compared to a standard. For beryllium, Taylor and Arnold (299) proposed gas chromatography for biological specimens. The beryllium was converted into its trifluoroacetylacetone complex and a n aliquot was injected into a chromatograph equipped with an electron-capture detector, with nitrogen as carrier gas and with columns of 10% SE-52 silicone gum on Gas-Chrom Z a t 110 "C. Norwitz and Galan (226) determined antimony in sebacatebase lubricants by digesting the sample with HzS04HN03, and treating a n aliquot of the resulting solution with KI and NaH2P02. The extinction was measured a t 425 nm and compared to another aliquot containing no reagent. Nickel, P l a t i n u m , Bismuth, a n d Thorium. Alder and West ( 1 ) determined nickel in fuel oils by atomic-absorption spectrophotometry. The sample was applied to the filament of the instrument with a micro-pipet and the metal was atomized a t 2700 "C. The absorption was measured at 232 nm or 231.1 nm and referred to a calibration graph. Wilkinson and Toth-Allen (339) irradiated biological samples containing platinum to produce a daughter nuclide, Ig9Au. The sample was digested, the platinum retained on a n ion-exchange resin, and the column counted in a well-type NaI(T1) detector used in conjunction with a 512-channel analyzer to measure the 158-keV y-ray activity. Hall and Farber (119) used atomic-absorption spectroscopy for bismuth in body tissue and fluids. After

A N A L Y T I C A L C H E M I S T R Y , V O L . 46, N O . 5, A P R I L 1974

digestion, the bismuth was extracted into isobutyl methyl ketone as its complex with ammonium pyrrolidine-l-carbodithioate. The absorption of the extract was measured with a n air-hydrogen flame a t 223.7 nm. Ohno and Ichikawa (231) proposed neutron-activation analysis for thorium in bone samples. The bone was ashed, dissolved in nitric acid, the thorium adsorbed on a n ion-exchange resin and eluted with 1M-IN03. An aliquot was irradiated and the activity of the induced 233Pa was counted after separation by extraction into trioctylamine-xylene from a solution containing HCl and ascorbic acid. T h e photopeak a t 0.32 MeV was measured with a 100-channel pulse-height analyzer. General Procedures. Fernandez (85) determined total metals in lubricating oils by high-frequency complexometric titration. 'The sample was mixed with' excess 0.025M 1,2-diaminocyclohexanetetraaceticacid and the excess reagent was titrated with 0.025M CaC12, the end point LITERATURE CITED (1) Alder, J. F., West, T. S., Anal. Chim. Acta, 61, 132 (1972). (2) [bid.. 58, 331 (1972). (3) Alicino, J. F., Microchem. J . , 16, 450 (1971). (4) /bid., 18, 350 (1973). (5) Anderson, D. H.,Evans, J. H..Murphy, J. J., White, W. W., Anal. Chem., 43, 1511 (1971) (6) Angelikva, R., Khig. Zdraveopazvane, 14, 517 (1971). (7) Arroyo, A,, Brune. D., Mikrochim. Acta, 1972,239. Aue. W. A.. Gerhardt, K. O., Lakota, S.,J. Chromatogr., 63, 237 (1971). Avgushevich, I. V . , Kulikova, E. S., Zakharova, A. A,, Velichko, Y. M . , Zavod. Lab., 38, 150 (1972). Balazs, N . D . H . , Poie, D. J . , Masarei, J. R . , Clin. Chim. Acta. 40, 213 (1972). Bartos, H . , Pesez, M., Bull. SOC. Chim. Fr., 1971, 345. Basson, W. D., Boehmer, R. G., Analyst (London), 97, 266 (1972). Bates, T. H.,Boyd, T. H.. ibid., 95, 955 (1970). Bazalitskaya, V. S., Alekseeva, N N . , lzv. Akad. Nauk. Kazakh. SSR, Ser. Khim., 1971, 66. Becker, D . A,, La Fleur, P.D., Anal. Chem.. 44, 1508 (1972). Bek, F . , Janouskova. J . , Moldan, B . , Chem. Listy, 66, 867 ( 1 972). Bernegger, A., Keller, H., Wenger. R., Z. Klin. Chem. Klin. Biochem., 10, 359 (1972) Bigois. M., Talanta, 19, 147 (1972). /bid., p 157. Binkowski, J., Mikrochim. Acta. 1971, 892. Binkowski, J., Wronski, M . , /bid., p 429. Bishara, S. W., Attia, M. E., Talanta. 18, 634 (1971). Bishara, S. W., Attia. M. E., Microchem. J.. 18, 267 (1973). Bock, R . . Thier. W., Fresenius' 2. Anal. Chem.. 253, 123 (1971). Borda, P., Crease. A. E., Legzdins, P., Microchem. J.. 18, 172 (1973). Bowen, H . J. M . , Analyst (London). 97, 1003 (1972). Bratzel, M. P., J r . , Chakrabarti, C. L., Anal. Chim. Acta, 61, 25 (1972). Bresler, P. I . , Kogan, D. K . , Shumakovich, M M . , Gel'man, N. E., Zavod. Lab., 37, 278 (1971). Brune, D., Arroyo, A , Anal. Chim. Acta. 56, 473 (1971). Byrne A. R . , Radiochem. Radioanal. Lett., 7, 287 (1971). Calme. P.. Gerhard, J. P., Kraeminger, E . , Mikrochim. Acta, 1972, 173. Cairne. P., Keyser, M . , ibid.. 1971, 644. Campbell, K.. Palmer, J. M . , J . Inst. Petrol.. 58, 193 (1972). Campiglio, A., Farmaco. Ed Sci., 26, 333 (1971) lbid.. p 349. Carnpiglio. A., Mikrochim. Acta. 1972, 631 lbid.. 1973, 169. Carter, J. M . , Analyst (London), 97, 929 (1972).

being detected with a high frequency oscillator. Reeves and coworkers (257) used the technique of atomic absorption spectroscopy with a graphite-rod atomizer for wear metals in engine oils; silver, chromium, copper, iron, nickel, lead, and tin could be determined. Kaiser, Tschoepel, and Toelg (154) decomposed organic samples containing traces of metals with activated oxygen. The sample was ashed a t low temperature in a quartz tube containing a cold-spot condenser and inserted in 'a micro-wave cavity resonator. Purified oxygen passing over the sample a t the bottom of the tube was excited by a micro-wave generator. The residue was dissolved in acid and analyzed. For mercury, a special trap cooled by liquid nitrogen was used. Schulte, Henke, and Tjan (275)determined 28 trace elements by activation analysis after separation by solvent extraction and precipitation. The elements were separated into six groups and the radionuclides determined by y-ray spectrometry.

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(114) Greweling, T., Bache, C. A . , Lisk, D. J., J. (161) Kirsten, W. J., Microchem. J., 1 6 , 610 (208) Merz, W., Brodkorb. E., Kranz, M., ibid., Agr. FoodChem., 2 0 , 4 3 8 (1972). (1971). 1972,939. (115) Grigor'yan, V. P., Levina, A. G., Zavod. (162) Koch, K.-H., Schmitz, L., Loose, W., (209) Mesrnan, B. B., Smith, B S., Pierce. J . Lab.. 38, 1449 ( 1 9 7 2 ) . Arch. Eisenhuettenw. 42, 8 8 3 ( 1 9 7 1 ) . O., Amer. lnd. Hyg Ass. J., 31, 701 (116) Gruenert, A . , Toeig. G., Talanta, 18, 881 (163) Koziowski, E., Kobylinska-Mazurek, B., (1970). (1971). Chemia Anal. (Warsaw), 16, 1169 (1971). (210) Mettler Instrument Corp. Princeton, N.J., (117) Grundon, N. J., Asher, C. J., J. Agr. Food (164) Kozlowski, E.. Kobylinska-Mazurek, B . , "Mettler-Heraeus Automatic Nitrogen AnaChem.. 20, 794 (1972). lyzer (1973). and Biziuk..M.,ibid., 1 7 , 109 ( 1 9 7 2 ) . (118) Gundersen, E., Steinnes, E., Talanta, 1 8 , (165) Kramme, D. G., Griffen. R . H., Hartford, (211) Mikhailova, T. A.. 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Thermal Analysis C. B. Murphy Xerox Corporation. Rochester, N. Y . 74644

This review covers the major trends in thermal analysis from the previous review (169) to October 1973. During this period. a new journal, Thermal Analysis Abstracts, edited by J. P. Redfern, has made its appearance. Its comprehensive keyword indexing system should make literature searching easy. Several books have appeared, including “Differential Thermal Analysis, Vol. 2, Applications” (134): “Atlas of Thermoanalytical Curves” (126),

based on results obtained with the Derivatograph; a revision of Schultze’s “Differential Thermal Analysis” (201); and “Thermogravimetry: Critical and Theoretical Study, Utilization, Principal Uses (227). A chapter, Thermal Methods, appeared in “Physical Methods in Macromolecular Chemistry” (138). The review of the analysis of high polymers (161) continues to provide excellent coverage of thermal methods.

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