Review of Fundamental Developments in Analysis
Inorganic Microchemistry Philip W . Wesf, C o d e s Chemical laborafories, louisiana Sfofe Universify, Bafon Rouge, la.
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the past two years, inorganic microchemistry has progressed steadily, but without spectacular innovations. Anyone following the literature closely must be impressed with the growing interest in microchemical and ultramicrochemical methods. Without question, the emphasis in analytical chemistry tends toward trace analysis and microchemical methods with spccial emphasis devoted to physical-chemical methods. Although instrumental or physical-chemical techniques are often applied to macroanalyses, the preponderance of applications is in the area of trace and microanalyses. As pointed out in the previous reviews of inorganic microchemistry, any appraisal of developments in this area must include consideration of speciaIized fields such as polarography, chromatography, fluorimetry, various electrometric methods, nucleonics, microscopy, and various forms of spectroscopy. Although little emphasis can be paid to these associated fields in the review of inorganic microchemistry as such, brief mention a t least must be made of the sophisticated developments in flame photometry, as well as the growing importance of activation analysis. Certainly it is important to add emphasis here to comments elsewhere devoted to atomic absorption spectroscopy. This field promises to be one of the major contributions to the determination of small amounts of metals. The method is proving very reliable m-hen applied to widely diverse types of samples, and the equipment and techniques required are simple when compared with some of the other methods now in use. Methods of separation and the development of new masking agents have attracted increased interest. The trend toward the use of organic reagents continues, and it seems safe to say that the bulk of the chemical methods applied to inorganic microchemistry involves the use of various organic reagents. The present review stems from impressions obtained from reading over 3000 references. The review extends from that published in 1960 (211) through the December numbers of CHEMISTRY and Analytica ANALYTICAL Chimica Acta and the November issue of Analytical Abstracts. OR
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REVIEWS
For purposes of orientation, the previous review of inorganic microchemistry (211) should be consulted, together with the other reviews of fundamental developments in analysis (11). Qualitative inorganic analysis has been reviewed from the standpoint of the microchemist by BenedettiPichler (21) and hlaurmeyer (132). hlaurmeyer has also discussed the developments in quantitative inorganic analysis (1%) with special consideration of microchemical methods. A special review of the principles and methods of the ring oven technique has been presented by Stephen (190) and kinetic methods have been reviewed by YatsimirskiI (228). Monnier (140) has discussed various aspects of trace analysis and problems associated with this technique. A comprehensive review of techniques and apparatus of importance in ultramicroanalysis has been presented by Sanz (1Z),and Alimarin and Yakovlev (6) have revien-ed the special problems of determining trace impurities in semiconductor materials. A summary of qualitative analysis methods on the microscale has been presented by Waldmann (200s) in which he discusses typical spot tests and microscopical procedures. The historical rcviem by Duval (44) presents a fascinating survey of 18th and 19th century investigations in microanalytical investigations. For purposes of orientation, the reviews of atomic absorption spectroscopy by RSenzies (138) and Robinson (161) are highly recommended. Likewise, the reviews of flame photometric methods by Dean (38) and by Mavrodineanu (154-6) should be consulted. High frequency techniques for determining titrimetric end points or for direct study of binary systems are often valuable in microchemical investigations, and the review of the theory and types of equipment used in radio-frequency methods has been presented by Ladd and Lee (105). The electron probe is providing very exciting possibilities for the quantitative determination of the elements above atomic number 11. This versatile tool can be used to study any selected surface. Less than 1 picogram of material can be analyzed, and the study can
be concentrated to an area of 1 square micron. A beam of 10- to 50-k.e.v. electrons is focused so as to escite characteristic x-ray spectra. Standard x-ray optics are employed for ultimate measurement, and the studies can be applied to diverse problems, such as the investigation of points of corrosion, the nature of thin surface layers, and the study of isolated inclusions in minerals and alloys. A concise discussion of this method has been presented by Birks (23) who is the developer of this technique. An interesting review of separations of inorganic ions by gas, liquid, and solid-phase distribution procedures has been presented by Kest (d16), and a general discussion of solvent extraction procedures has been given by Trbmillon (198). A review of benzidine and its derivatives has been presented (115), and a pertinent review of the application of EDTA as a microanalytical reagent has appeared (18). This latter discussion covers the use of EDTA in masking interfering ions and in microtitrations. It also points out the use of this reagent as a chromogenic reagent and further describes its applications in polarography, electroanalysis, and chromatographic and ion exchange methods. Lavruchina has discussed the behavior of ultramicro amounts of elements during precipitation, extraction, electrolysis, distillation, and chromatographic separations (108). The problem of blanks in the analysis of traccs has been discussed (98), and the special case of errors arising from the use of polyethylene bottles has been considered (196).
Precision and accuracy together with the use of corrections to improve accuracy are always important to the microanalyst. Detection limits and precision have been discussed by Wilson (bdl), and corrections to be used in micro analytical neighing have been considered (43). Liken-ise the problem of sample preparation has been considered by Schulek and Laszlovszky (174) who have given special consideration to the problem of destruction and dissolution of samples. They have also considered methods for collecting trace materials from large samples of matrix materials. Unsuspected individual
errors, particularly regarding the last place of decimals in micro weighing, have been noted, and suggestions are made for a new technique for reducing errors (64). Special consideartion has been given to relationships of structure of complexing agents and the stability of metal complexes (175). Likewise, consideration has been given to means for increasing selectivity in chelate formation (215). Those interested in voltammetry will find the theoretical discussion of stripping voltammetry with spherical electrodes by Reinniuth of interest, (159). The continued adrances in flame photometry are proving significant in microanalysis, and the various parameters affecting flnnie beharior are, of course, important. The effect of sample flow rate has bctn studied (58),and various factors such as the composition and temperature of flames and the nature of sample sprays have been discussed (53). The problem of mutual cation interference in flame photometry has been considered (541. Terminology is always an important consideration, and a system of classification of terms in microchemical analysis has been proposed (78). Terminology to be used for work with precision balances has been suggested (79). A report has been presented on the standardization of terminology prrtaining to pH and related measurements (77), and a classification and nomenclature of significance to electrochemical methods has been described (40). Finally in the nature of review, the summary of papers presented a t the summer symposium of the Analytical Division dealing with trace analysis is of interrst ( S I ) , as is the summary of papers prescnted a t the summer symposium dcaling with complex reactions in analyticsl chemistry (158). APPARATUS A N D INSTRUMENTS
The special requirements of niicroand ultramicrosnalysis lend emphasis to developments of apparatus and refined cquipnient . Microbalances are of prime iniportnnce, and a Tyide variety of types arc avai1:iblc commercially or can lie made simply. Bonting and hlnyron have described a quartz fiber “fishpolc” ultramicrobalance (28) and have given construction details, as well as methods of calibration and possible usrs of the balance. They constructed 14 of the b:tlnnces in their on-n laboratories and found that in every case, a linear relationship was obtained between deflection and load, and the reproducibility of replicate weighings was eucellent. The useful load of this type of balance is generally considered to be approximately 30 pg. Therefore, the suggestion of Thomas (197) for extending the useful load is significant.
He proposes the use of specimen carriers made from small sponges of polystyrene foam for weighing dispersed materials. The sponges are weighed and subsequently soaked with the suspension or solution of the sample. After evaporating the solvent, which is ordinarily ethyl alcohol or water, the sponges are reweighed to determine the weight of nonvolatile material trapped. The polystyrene sponges may be destroyed by ashing or by dissolution, using suitable solvents. The problem of isolating microbalances against vibrations has been discussed by Kissa (91) with the conclusion that balances can be mounted with properly selected springs, thus protecting them from disturbing vibrations, except for those of very low frequencies. Bolting the balance to the mount appears to be advantageous. Rigid mounts without resilient parts neither absorb nor magnify vibrations, while indiscriminate use of resilient materials in the mount may lead to the amplification of vibrations. Apparatus of importance in volumetric measurements has been the subject of recommendations by the American Chemical Society Committee on hficrochemical Apparatus. The committee has recommended specifications for micropipets of various types (10). A volumetric microburet, a gravimetric microburet, and a titration table for use in microchemical work have been described (155), and the use of polyethylene micropipets has been recommended (130). A simple ultramicroburet was developed by Habermann employing a micrometer screw for delivery of accurate volumes of solution (65). A modification of the Habermann buret has since been suggested (2Z4) Absorption cells for spectrophotometric work have been studied and an improved microliter cell for use with the Beckman Model DU spectrophotometer has betn proposed (62). Infrared studies have become increasingly important in inorganic microchemistry, and Lippincott and Welsh have described a cell employing diamond or sapphire windows which can be used in obtaining spectra of corrosive liquids and various solids. X i t h the cell, it is possible to examine specimens weighing as little as 4 pg. (111). A comprehensive discussion of apparatus and techniques of importance in ultramicro studies has been presented by Sane (172). A broad selection of equipment is considered, including pipets, burets, photometers, centrifuges, p H meters, electrodes, and beakers. Density gradient columns have been used in certain specialized areas for a considerable period of time. Kirk has pioneered in the use of such columns for identifying soils, glasses, etc. in crime investigations. Other areas
n-here such columns have proved useful include polymer studies and air pollution investigations. The preparation of density gradient columns has been described by Lindsley (110). I n addition to the electron probe technique, the use of atomic absorption spectroscopy is attracting wide attention. This review cannot consider a complete coverage of this field, but the work of Walsh should be studied for proper historical orientation. hfenzies has discussed the instrumentation of atomic absorption spectroscopy (138), and hialmstsdt and Chambers (125) have described an instrument employing the null point principle for use in this field. There seems to be a tendency for instrument manufacturers to promote very sophisticated equipment. While it is to be admitted that refinements in design and construction may be very important in some instances, it must be recognized also that relatively simple equipment may often be all that is required. I n the case of atomic absorption spectrometers, it appears that there is a disproportionate emphasis on elaborate equipment, and it may be well, therefore, to see the paper by Box and Walsh who have described a simple spectrometer that is capable of giving highly reliable results for most applications (29). SEPARATIONS
Methods of separation, isolation, and masking continue to gain in importance. Within the past few years, masking has been universally applied for eliminating interfering effects. Gathering agents or collectors have attracted a great deal of attention because of the increased interest in determining trace materials. Solvent extraction methods are now firmly established for practically every type of separation problem, and even anions are now being separated by this means. Kice methods of separation which depend on volatilization techniques, and novel methods of electrodeposition, ion migration, and precipitation appear in increasing numbers in the microchemical literature. The problem of decomposing refractory silicates for ultramicroanalysis has been studied by Sill (186), and the elegance of masking as a means of climinating interferences has been demonstrated in the work of Lott, Cheng, and Kwan a-ho used various masking agents (113) to establish a highly selective spectrophotometric method for determining thorium with Eriochrome Black T. Volatilization methods work nicely in many types of microchemical applications. Marshall has employed a distillation procedure for separating lead from rocks and meteorites ( l a g ) , VOL 34, NO. 5, APRIL 1962
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and Shvarts (186) has been able to determine trace metals in high purity nickel by volatilizing the nickel matrix as nickel carbonyl and subsequently examining the residue for trace amounts of contaminating metals. The Conway cell has been used for the determination of chlorine, bromine, and iodine by
Table
I. Separation, Isolation, an Masking
Remarks Reference Subject Actinides Electrodeposition Actinides Triiso-octylaminexylene estn. from chloride soln. Hg as collector Ag Masked with glu.4l conate Acetylacetone A1 masking Benzene extn. As Hg as collector Au Extn. of methylene B blue tetrafluoroborate Acetylacetone Be Extq. of iodide Bi using isoamyl acetate and isoamyl ale. Ca N,N-di( hydroxyethy1)glycine masking Cd Fe(OH), as collector Unithiol masking Cd MnOl as ccllector Fe Masked Kith gluFe conate Ga Ti(OH), gather (104) Ge Isobutyl methyl ke- (181) tone extn. from HC1 soln. Unithiol masking (201-8) Extn. as cadmium ($12) iodide 8-Quinolinol extn. hfg Xb Isobutyl methvl ketone extn. -from HC1 soln. Methyl isobutyl keNp tone extn. Pb Unithiol masking Pd Bcetylacetone masking EDTA masking Pd Methyl isobutyl kePu tone extn. Rare Bis(2-ethylhexy1)orthophosphoric earths acid extn. from HCl s o h . Extn. with py Re Se(IV) Fe(OH), as collect or Sn Sn14-benzene extn. Sn Tris( 2-ethylhexy1)phosphine extn. into cyclohexane Tc Extn. with pyridine Thiourea complexTe tri-n-butyl phosphate extn. Ti Masked vith gluconate HC1-tributyl phos]’(V) phate Y Tri-N-octylphosphine oxide extn. Zn Unithiol masking Zr Extn. with di-nbutyl . phosphate .
B”
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employing a combination of microdiffusion with isotope dilution (151). It can be anticipated that gas-liquid chromatography will play an increasingly important role in the separation and analysis of inorganic materials. Volatile metal halides have been examined by Keller who studied their behavior at various temperatures on different partitioning agents (88). Likewise, various metal halides were subjected to gas chromatographic separation (87) using a eutectic column of BiC13-PbC12 supported on Johns-Mansville C-22 firebrick. Solvent extraction techniques are proving invaluable for all scales of operation. The advantage of this method for isolating trace materials is obvious because of the ease with which repeated separation steps can be carried out. The flexibility of solvent extraction is of paramount importance, and it must be kept in mind that different types of separation can be obtained on any given species by using different extracting solvents or mixtures of solvents, or by changing the stripping operations. For examplp, McCown and Larsrn have shown that cerium(II1) extracts less than 0.1% into bis(2ethylhexy1)phosphoric acid, while cerium(1V) extracts better than 99%. This provides a means of separating the two oxidation states of cerium. Furthermore, these investigators point out (117) that fission products and actinides may extract m ith efficiencies of 98 to over 99%, but they are not backextracted if a stripping medium of 3y0 hydrogen peroxide in 1 0 N HXO, is used. Phosphzte can be separated from arsenate by solvent extraction (167‘). Manganese can be quickly and selectively isolated by extraction of tetraphenylarsonium permanganate into nitrobenzene (131), and excellent extraction methods have been proposed for the isolation of zinc (188) and niolybdenum (122). Boron can be neatly isolated by extracting the methylene blue tetrafluoroborate into dichloroethane (154). Shibata (184) has pointed out the usefulness of 1-(2pyridylaz0)-2-naphthol as a chelating agent for extracting various metals and butyl rhodamine has been suggested as a versatile agent for extracting elements that form hydrophilic complex anions in acidic solution (101). I n the past, the emphasis on solvent extraction methods has been on the separation of cations, but it should not be overlooked that anions can also be isolated with these procedures. For example, West and Lorica demonstrated the Pfficient isolation of iodide by extracting cadmium iodide into a 1 : l mixture of tri-n-butyl phosphate-methyl isobutyl ketone (213). The recovery of iodide from the nonaqueous phase was accomplished using a -solvent displace-
nient technique in which carbon tetrachloride was added to the nonaqueous layer, and the cadmium iodide recovered into a sodium hydroxide solution. The alteration of the nonaqueous phase in this case demonstrates dramatically the influence of the solvent in the extraction process. The subject has been evplored in detail by Specker, Jackwerth, and Hovermann (189). During most of the previous reviews of inorganic microchemistry, special attention was called to masking agents because there was no single source for reference in this regard. Although many of the masking agents have been common knowledge, the previous reviews were the only source where they could be found tabulated. Table I in this review refers to additional examples of masking, along with other methods of separation that appear to have special interest. dlmAssy and VigvAri have shown how various masking agents can be used to condition a nonselective reaction (9). They employed morin for the microdetermination of molybdenum(V1) and m r e able to eliminate a wide variety of interferences by the simple expedient of adding EDTA and sodium fluoride. They n-ere also able to eliminate most interferences by using oxalic acid as a complexing agent. Although it may be open to debate, EDTA often seems to be more valuable as a masking agent than it is as a titrant. So many systems have been conditioned using EDTA that it is scarcely practical to try to list all of the applications. The simplicity of technique that can he obtained n-ith masking is shown by the u-ork of Lima and Abrgo who srparate lead from bismuth (109) by adding EDTA to the system and folloir ing this by sodium hydride precipitation of the bismuth hydroxide. The method is rapid, simple, and effective. Various complexing agents are also invaluable in establishing systems for paper electrophoresis ( $ I O ) , and of course, in the selective elution of metals from ion exchange columns. Chromatographic and ion exchange methods are reviewed elsewhere, but special applications warrant attention in the review of inorganic microchemistry, Ion exchange resins as reaction media are proving very helpful, and the work of Fujimoto has served to pioneer developments in this area (56-7). A “ligand exchange” method described by Helfferich (68) has interesting possibilities. Various ligands are absorbed on ion exchange columns containing metal ions such as copper, nickel, silver, or cobalt. Exchange of ligands can be obtained without displacing the metals, and a system of exchange chromatography results. ilnother interesting possibility in the field of ion exchange separations has been pointed out by
Seidl and Stamberg who synthesized a chelate resin from flurone derivatives and formaldehyde (f78) which was selective for germanium. Using the scilective exchange medium, it is possible to isolate germanium from arsenic and iron, even in the presence of concentrated HC1. I n more general work, cation exchange chromatography has been used to separate various trace elements in plant materials from large quantities of iron (f92), and a series of studies on the concentration and separation of trace elements by ion e-ichange methods has been made by van Erkelens (48-50). The Weisz ring oven is now firmly establishrd as one of the major tools for analytical separation a t the niicrogram level. As an adjunct to spot test procedures, this separation tool finds wide application. It is important to note also that its use is not limited to separation processes, but in addition, it serves to establish spot test procedures on a semiquantitative and even quantitative basis. The recent appearance of the book on microanalysis by the ring oven technique by Weisz should be a valuable addition to the microanalyst’s bookshelf (207). Many applications of the ring oven technique are being described. Ackermann (2) has employed the ring oven in systematic studies of trace impurities in alkali and alkaline earth metal salts. West and Weisz have used the technique for the transfer, concentration, and analysis of collected air-borne particulates (214). The technique has proved of value in the detection of thorium (66), and Malissa and Ottendorfer have used the ring oven for the detection of small amounts of various cations that yield insoluble dithiocarbamates (124). The ring oven method is applied usually to spot test reactions in which the final reaction product is localized in the form of a precipitate. Weisz and R e s t have shown, however, that soluble reaction products which might otherwise diffuse widely on paper can be concentrated by use of the ring oven (209). The test sensitivity in such cases may be increased by one or two orders of magnitude because of the effect of localization. Amalgams are proving useful in microchemical separations. Cadmium has bc>enseparated by an amalgam eychange process (41), and the lanthanons have bren isolated from a lithium citrate electrolyte by electrolysis a t an amalgam cathode (162). It should not be overlooked that the use of mercury can provide an extremely effective means for quantitatively collecting silver and the noble metals (119). Various precipitation reactions have been used for separating or concentrating small amounts of material of interest in microanalysis or trace analysis. Mixed precipitants
are effective in isolating small amounts of material for subsequent examination by spectrographic or other procedures. For example, 8-quinolinol and thionalide serve nicely for such purposes (39)*
coprecipitation has attracted renewed interest as a means of collecting small amounts of material from dilute systems or from systems containing gross amounts of possible interfering substances. Alimarin and Bragina have separated small amounts of cobalt from large amounts of nickel by the coprecipitation of cobalt with Rhoz(4). hlorachevskil and his covorkers have succeeded in collecting gallium and zinc with calcium phosphate under carefully controlled conditions (142), while under different conditions they were able to collect aluminum on calcium phosphate, while leaving gallium completely in solution(143). Iron has been concentrated from very dilute aqueous solutions using M n 0 2 as the collector (153), and ultramicro amounts of alkaline earth elements have been concentrated by cocrystallization with potassium rhodizonate (206). Silver has been collected using tellurium as carrier (100). Selenium has been coprecipitated with Fe(OH)3 (156). Vanadium has been collected with A1(OH)3 (225)) and small amounts of tin and antimony have been isolated by coprecipitation (42) with MnO2 as the collector. Thallium has been collected from dilute systems by coprecipitation with barium or lead as the chromate or sulfate ( 9 4 , by coprecipitation with the thiourea complex of lead (46), and by the use of Biz& combined with potassium tetraphenylborate (170). The precipitation of chelates has generally been considered relatively free of tendencies toward coprecipitation. However, some organic precipitants are proving useful as collectors. Kuznetsov and Akimova (101) have collected plutonium from dilute solution by coprecipitation of the nitrate with the nitrate of rhodamine B butyl ester. A systematic study of coprecipitation by organic precipitants is being undertaken by Korenman and his associates. They have collected zinc, cadmium, and mercury with copper anthranilate (93). Thallium is coprecipitated with the bromination products of diamonoazobenzene (95). Zinc is gathered by a precipitation with nickel using an ammoniacal Xaphthol Yellow solution (96), and cobalt is collected by precipitating nickel dicyandiamidinate (99). REAGENTS
The standardization and verification
of reagents involve the use of reference materials. Hoffman (72) has discussed the important role of reference standards in the development of new methods to-
gether with various other aspects of standard materials. At one time, it was considered highly unlikely that selective or specific reagents could be found for calcium or other alkaline earth metals. Since the introduction of glyoxal bis(Zhydroxyani1) in 1958, a number of excellent reagents have been suggested. Close and West (36) have introduced Cnlcichrome for the detection and compleximetric titration of calcium. The ultramicro estimation of calcium can also be accomplished with the dye Erio SE (32), and small amounts of calcium can be estimated colorimetrically using 2-hydroxy-2’-(2hydroxy - naphthylazo) - 5 - methylazoxybenzene (46). Korenman and Ganina have described color reactions for barium using Lacquer Scarlet S, and for calcium, using 3-(o-hydroxyphenylazo)chromotropic arid (97). They also describe color reactions of calcium with 3- (4-sulfophenylazo) chromotropic acid and Acid Monochrome Bordeaux S. Many fundamental studies of aminopolycarboxylate ligands have appeared (74, 90, f 73). The lead salt of diethyldithiocarbamate has been proposed as a specific reagent for copper (3). The dihydroxylamine salt of dihydroxymaleic acid is claimed t o be specific in its reaction with traces of titanium (IV) (f93), and six derivatives of 1,lOphenanthroline have been prepared, and the complexes they form with iron(I1) have been studied (67). A fundamental study of the reaction between 2,2‘,4‘trihydroxyazobenzene - 5 - sulfonic acid and zirconium has been carried out (62), and similar fundamental studies have been made of the sulfonic acid derivatives of 1 , l O phenanthroline and their reactions with iron(I1) (2b). Various reagents containing heterocyclic nitrogen and the SH group, as well as two thiourea derivatives, have been investigated as possible reagents for osmium (16 ) . An interesting study of o-hydroxybenzenesulfinic acid as an analytical reagent has been niade by Alimarin and Kuznetsov (5). They have found that the new reagent possesses most of the chemical properties characteristic of salicyclic acid, but it reacts in more acidic media and thus has a number of advantages from the analytical point of view. The fundamental studies by Neely and Williams of the reaction between Schoenberg’s reagent and elemental sulfur are of interest (148). Pyrocatechol Violet is a sensitive reagent for tin(IV), although there are a number of interferences (168). Because most reagents now available react with tin(II), the new reagent is of considerable importance in spite of the interferences. QUANTITATIVE METHODS
Gowda and Stephen (63) have proposed a new reagent for the detection VOL. 34, NO. 5, APRIL 1962
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and gravimetric determination of sodium. They have found that 5benzaminoanthraquinone-2-sulfonicacid is a most sensitive precipitant for sodium, being able to disclose as little as 5 pg. of sodium. Unfortunately, there are many interferences. The ultramicro gravimetric determinations of technitium and rhenium have been accomplished by precipitation with tetraphenylarsonium ion (83). Many interesting innovations have appeared in the area of titrimetric procedures. A new indicator for the ultramicrotitration of calcium has been proposed ( 2 0 4 , and a microphotometer has been developed for determining the exact end points of colorimetric or nephelometric titrations insmall volumes (73). The titration of extremely dilute systems has been accomplished in a number of ways. Cyanide has been titrated by direct amperometry (116), and high frequency titrations have been very effective for use with dilute systems (146-7, 171). Voltage scanning coulometry has been used for the determination of very small amounts of iron (176), and silver and copper have been titrated a t the parts per million level using null point potentiometry (126). Null point potentiometry has been used for determining microamounts of oxidants and reductants (127). Thiosulfate is not used as a titrant, thus eliminating errors associated with the iodine-thiosulfate titrations. Standard iodine solution is not required, and instead, electrolytically generated iodine is employed. Microcoulometry has been employed for the determination of hydrazine a t the microgram level with remarkable accuracy (24), and a coulometric moniter has been developed for the automatic determination of borane a t the parts per million level or less ($0). The semiquantitative determination of a number of metals by ring oven techniques has been described (33), and a quantitative spot test procedure for determining halogen in a single drop has been proposed (17). The study by Hora and Webber of sources of error in the phenoldisulfonic acid method for nitrates is of interest (7’6). Special attention is directed to the use of extraction methods for the isolation of metals followed by the subsequent direct color development in the nonaqueous phase (169,177). This approach avoids the tedium of back-extracting the desired species, and of course, presents the inherent advantages of selectivity obtained by the extraction process and the selective nature of reactions occurring in nonaqueous systems. Ultraviolet spectrophotometry has been used in determining tin(1V) as a chloro complex (80), and infrared measurements have been used in analyzing minerals (199) and determining traces of sulfate in reagent chemicals (34). The 108 R
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advantage of fluorometric methods is evidenced in the procedure described (218) for the estimation of aluminum in the parts per billion range. The advantages of coulometry a t controlled potential for submicrogram scale analyses have been pointed out by Rfeites (137), and Kemula and Kublik (89) have described the use of a stationary hanging mercury drop electrode for determining low concentrations of copper, lead, cadmium, and zinc. Anodic stripping voltammetry offers great possibilities in the study of ultramicro amounts of material. Nicholson has used the technique for determining and as little as 3 p.p.b. of nickel (1~$9), fundamental contributions to this technique are due to the work of S h a h and his associates (182-3) who have been responsible for much of the development in this field. Catalytic reactions have been established for some time as remarkably sensitive and often selective or specific means for qualitative analysis. Increased interest in quantitative applications is noted, especially for the determination of submicrogram quantities of material. Surasiti and Sandell have utilized the catalytic effect of ruthenium on the reaction between cerium(1V) and arsenic(II1) (194). By noting the time required to reach a given absorptivity value of a solution containing the reactants, they were able to determine ruthenium in the range of 0.005 to 0.1 fig. The reactions between chloramine T and tetrabase are catalyzed by the presence of iodide as noted by Feigl. This reaction has been adapted (85) for the ultramicro cletermination of iodine in water. Erdey and SzabadvBry have used a catalytic reaction for determining iron in the nanogram range (47). Laszlovszky has proposed catalytic methods for determining traces of cobalt (1006--7), and BognBr and Jellinek have also studied the catalytic determination of cobalt (66). Czarnecki has combined amperometric measurements with a catalytic reaction for the determination of copper (37). Q UALlTATlVE METHODS
The importance of the reaction medium in analytical reactions is often overlooked. For any given medium, small variations may often have a pronounced effect. For example, in the case of spot tests, changing the types of papers may result in changes of sensitivity of one to two orders of magnitude. An investigation of 69 varieties of filter paper has been made by Ackermann ( I ) who concluded that the variation in sensitivity found in different papers was due to differences in the exchange capacity. It is safe to predict that there will be more and more emphasis on reactions of
extreme sensitivity. An indication of the types of approaches that may become common is given by three papers dealing with tests applicable to the picogram range. Weisenberger used electrodeposition of copper followed by reaction n.ith picrolonic acid and ultimate examination by electron microscopy to detect 5 x IO-” gram of this metal (217). A catalytic test for cobalt (3‘7) is applicable in the picogram range, and Stolyarov and Grigor’ev (191) have used a luminescence method for detecting antimony in as little as gram. Highly selective or specific reactions are always of interest. Jungreis and Lerner have utilized the demasking action of aluminum on calcium fluoride as a specific test for aluminum (86). The calcium released in the demasking action is detected by the highly selective and sensitive glyoxal bis(2-hydroxyanil) reaction. Cadmium has long been one of the most troublesome of the common metals to detect. Vest and Diffee (212) have proposed a specific and sensitive test utilizing glyoxal bis (2-115.droxyanil). The reaction is carried out on beads of an anion exchange resin which is used to concentrate cadmium and isolate it as the tetraiodo complex. Studies of anthraquinone derivatives as reagents for boric acid have been described (98). Substituted naphthalenes have been investigated for the fluorimetric determination of tin (IS), and new reagents for the detection of technitium (84) have been proposed. A substituted chroniotropic acid (55) has been suggested as a reagent for titanium, and a sensitive and selective procedure for the identification of scandium (2000) is based on the reaction with carminic acid in the presence of BaSO, carrier. p-Phenylenediamine has been investigated (145) as a reagent for the spot test identification of ruthenium(III), and two new spot tests for gold have been suggested (179, 188). Gallium has been detected by collecting it on a fresh suspension of A1(OH)3 m-ith subsequent identification by alizarin in the presence of oxalate (103). The 2,4dinitrophenylhydrazone of diactyl monoxide has been described as a new sensitive reagent for cobalt (12). A new spot test for fluoride employing the cerium(II1) chelate of alizarin complexone has been proposed by Eelcher, Leonard, and West, (20), and Weisz has suggested the detection of fluoride ion by the demasking of ferric rhodizonate (2069, n ith subsequent formation of blue-black silver rhodizonate. A special quinolhe-ammonium molybdate paper has been suggested for detecting trace amounts of orthophosphate (14). Finally, a qualitative analysis scheme for common cations is based on the use of 1-(2p y r i d y 1a z 0 ) -2-n a p h t h o l , commonly
known as PAN. Separation into two major groups (22) is obtained by pH control, and selective or specific tests are then used to detect individual ions n ithin the separated groups. MISCELLANEOUS
,A number of diverse contributions have special interest. Loy and his COR orkers have used a unique approach for the detcrrnination of the valence state of arsenic. They employed a biological assay (114) in which various arsenicals were studied t o determine their inhibitory effect on the growth of Lactobacillus leichmannii. A unique method for the estimation of copper has been suggested by Ropp and Shearer n ho employ a luminescnce activation approach (166). The copper is absorbed on silver-activated zinc sulfide, and a copper-activated phosphor results. A green fluorescence is obtained which is a direct function of the copper concentration and serves for the estimation of 0.01 to 500 p.p.m. of the metal. Exley claims that flame photometry employing acetone solutions and a n oxyhydrogen flame permits the detection of a number of metals in the picogram range (51). A Beckman flame photometer TI as modified to obtain enhanced sensitivity. Van Xeuwenberg has described a simple apparatus (150) which yields a direct reading of the correction required to convert micro and semimicro weighings to a normal temperature and pressure basis. A drill attachment for the microscope has been described which permits samples as small as 0.001 inch in diameter to be removed for subsequent analytical study (187). Some of the problems of microanalysis originate from unexpected sources. Huffmann found that erratic values for boron in mineral samples could be traced (76) to boron contamination from paper pill boves used in transporting samples. The report of Williams on the properties of various glasses ($19) is, therefore, of interest. l h e acid and alkali resistance, the thermal properties, and the trace metal content of different glasses are recordcd. Because of the videspread interest among microanalysts in the field of flame photometry, and more recently, atomic absorption spectrophotometry, the studies of flames and flame characteristics are of interest. Robinson has discussed (163) the mechanism of elemental spectroexcitation in flame photometry, and the role of organic solvents in flame characteristics has been discussed (8, 16, 162). A long path burner for atomic absorption work has been described (35). An excellent perspective of atomic absorption spectroscopy can be obtained from the article by Gatehouse and Walsh (69). A further introduction to this
fascinating technique can be obtained from miscellaneous articles, such as those dealing n i t h the determination of iron in manganese (Y), zinc (60), noble metals ( I I I ) , lead in gasoline (164), and calcium and magnesium ($20)* ACKNOWLEDGMENT
The assistance of Fe Ordoveza, Charles Herrin, Darrell Donaldson, G. C. Gaeke, Patricia R. LIohilner, Ch. Cimerman, and Albert0 J. Llacer in checking much of the original literature is gratefully acknowledged. Partial financial support from the U.S. Public Health Service under Grant 90.7481 is also gratefully acknowledged. LITERATURE CITED
(1) Ackermann, G., Mikrochim. Acta 1959, 357-69.
( 2 ) j b i d ; ; 1960, 771-4. (3) Adamiec, I., Rudy i Jletale .Viezalazne
5, 409-12 (1960). (4) Alimarin, I. P., Bragina, '4. A., Trudy
Komissii A n d . Khim. Akarl. S a i i k S.S.S.R. 12, 377-52 (1960). ( 5 ) Alimarin, I. P., Kuznetsov, D. I., Dokladv Akacl. 1YaukS.S.S.R. 131,821-4
(1960).(6) Alimarin, I. P., Yakovlev, Yu. V., Zavodskaya Lab. 26, 915-21 (1960). (7) Allan, J. E., Spectrochim. Acta 15, 800-6 (1959). (8) Ibid., 17,467-73 (1961). (9) Almbssy, G., Vigvbri, hl., Acta Chim. d c a d . Sci. Hung. 20, 243-51 (1959). (10). American Chemical Society Committee on Llicrochemical Apparatus, AXAL.CHEM.32, 1045-6 (1960). (11) ANAL.CHEM.32, 3R-292R (1960). (12) Anand, V. D., Deshmukh, G. S., .I'aturwissenschajten 46, 648 (1959). (13) Anderson, J. R. A., Garnett, J. L., Lock, L. C., Anal. Chim. Acta 22, 1-7 (1960). (14) Antoszewski, R., Knypl, J. S., Analyst 85,527-8 (1960). (15) Avni, R., Alkemade, C. T. J., illikrochim. Acta 1960, 460-71. (16) Baiulescu, Gh., Lazgr, C., Cristescu, C., Anal. Chim. Acta 24,463-6 (1961). (17) Ballczo, H., Hainberger, L., Mikrochim. Acta 1959, 466-72. (18) Barnard, A. J., Jr., Broad, W. C., Flaschka, H., Microchem. J . 3, 43-64 (1959). (19) Beard, H. C., Lyerly, L. A,, ANAL. CHEM.33, 1781 (1961). (20) Belcher, R., Leonard, bl. A., West, T. S., Talanta 2,92-3 (1959). (21) Benedetti-Pichler, A. A., Microchem. J . 3, 323-31 (1959). (22) Berger, W.,Elvers, H., 2. anal. Chem. 171, 185-93 (1959). (23) Birks. L. S.. ANAL.CHEM.32. 19A' 2SA (1960). ' (24) Bishop, E., Mikrochim. Acta 1960, \ - - - - ,
. . (27) Ibid., pp. 100-3. (28) Bontincr, S. L.. Mavron. B. R.. ' il?icroche$.'J. 5, 3i-42 (is61j. (29) Box, G. F., Walsh, A., Spectrochim. Acta 16, 255-8 (1960). (30) Braman, R. S., DeFord, D. D., Johnston, T. N., Kuhns, L. J., ANAL. CHEM.32,1258 (1960). (31) Brandt, W. W., Ibid., 32, 1595 (1960).
(32) Brush, J. S., Zbzd., 33, 798 (1961). (33) Cklap, M. B., Weisz, H., Mikrochim. Acta 1960, 706-12. (34) Citron, I., Underwood, A. L., Anal. Chzm. Acta 22, 338-44 (1960). (35) Clinton, 0. E., Spectrochim. Acta 16, 983-8 (1960). (36) Close, R. A., West, T. S., Talanta 5,221-30 (1960). (37) Czarnecki, K., Chem. Anal. (Warsaw) 5, 377-82 (1960). (38) Dean, J. A., Analyst 85, 621-9 (1960). (39) Dehm, R. L., Dunn, W. G., Loder, E. R., ASAL. CHEM.33,607 (1961). (40) Delahay, P., Charlot, G., Laitinen, H. A., J . Electroanal. Chem. 1, 423-33 (inmi
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(41) DeVoe, J. R., Sass, H. W.,Meinke, W.W.,ANAL.CHEM.33,1713 (1961). (42) Downarowicz, J., Zaghrski, Z., Chem. Anal. (Warsaw) 4, 445-54 (1959). (43) Durselen, W.,Z. Chem. 1, 119-23 (1961). (44) Duval, C., Xzkrochim. Acta 1960, 630-5. (45) Dziomko, V. M., Kalinina, K. E., Kuznetsova, L. K , Maslinikova, V. I., U.S.G.R. Patent 128,195 (April 28, 1960). (46) Efremov, G. V., Iiarysgina, S . E.,
Uchenye Zapiskz Lenzngrad. Gosudarst. Gnzv 1960, 71-6. (47) Crdey, L., Szabadvhry, F., Jfikrocham. Acta 1959, 424-31. (48) van Erkelens, P. C., Anal. Chim. Acta 25, 42-50 (1961). (49) Zbzd., pp. 129-35. (50) Ibzd , pp. 226-22 (51) Exley, D., Photoelectric Spectrometry Group Bull. l -.en h ~322-7. , (52) Fletcher. M. E[.. ANAL.CHEM.32, ' 1827 (i96oj. (53) Foster, W. H., Jr., Hume, D. N., ANAL. CHEY.31, 2028 (1959). (54) Zbzd., p. 2033. (55) Frum, F. S., Xistanova, G. A., Trudy Khim. i Khim. Tekhnol. 1958, 578. (56) Fujimoto, hlasatoshi, Chemist Analvst 49.4-10 (1960). (57)"Fujimoto, 'Masitoshi, hraturwissenschajten 47,252 (1960). (58) Fuwa. Xeiichiro. Thiers. R. E., ' Vallee. B. L.. Baker. hf. R.. ASAL: CHEM.31,203b (1959): (59) Gatehouse, B. M., Walsh, A., Spectrochzm. Acta 16. 602-4 (1960). (60) Gidley, J. A. F., Jones, J. T., -4naZyst 85, 249-56 (1960). (61) Gilbert, D. D., Sandell, E. B., Microchem. J . 4, 491-500 (1960). (62) Glick, D , Greenberg, L. J., ANAL. CHEM.32, 736 (1960). (63) Gowda, H. S., Stephen, W. I., Anal. Chzm. Acta 25. 153-8 (1961). (64) Ggsel, H., Chimia 13, 253-7 (1959). (65) Habermann, V., Chem. listy 53, 30-1 (1909). (66) Hainherger, L., Sanchez, S. Cuadrado, Xzkrochim. Acta 1961, 245-9. (67) Hankins, C. J., Duewell, H., Pickering, W.F., Anal. Chim. Acta 25, 257-61 (1961). (68) Helfferich,. F.,. Xature 189, 1001-2 . (1961). (69) Hikime, Seiichiro, Bull. Chem SOC. Japan 33, 761-5 (19GO). (70) Hirano, Shizo, hlizuike, Atsushi, J a ~ a nAnallist 8, 746-9 (1959). (71) *Hirano, Shizo, Mizuike, Atsushi, J. Chem. Soc. Japan, Ind. Chem. Sect. 62, 1497-9 (1959). (72) Hoffman, J. I., ANAL. CHEM.31, 1934 (1959). (73) Holasek, A., Lieb, H., Winsauer, K., Xikrochim. Acta 1959, 402-5. (74) Holloway, J. H., Reilley, C. N., ANAL.CHEM.32, 249 (1960). -1
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VOL. 34, NO. 5, APRIL 1962
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(75) Hora, F. B., Webber, P. J., Analyst 85, 567-9 (1960). (76) Huffmann, C., Jr., U. S. Geol. Survey., Profess. Paper, iyo. 400-B, 493-4 (1960). (77) International Union of Pure and Applied Chemistry. Commissions on Electrochemical Data and Physicochemical Symbols and Terminology, Pure and A p p l . Chem. 1, 163-8 (1960). (78) International Union of Pure and Applied Chemistry. Commission on Microchemical Techniques, Ibzd., 1 , 169-70 (1960). (79) Zbid., pp. 171-5. (80) Ishibashi, Masayoshi, Yamamoto, Yuroku, Inoue, Yasushi, Bull. Inst. Chem. Research 7 , 38-47 (1959). (81) Jablonski, W. Z., Johnson, E. A., Analyst 85, 297-9 (1960). (82) Jankomki, S. J., Freiser, Henry, ANAL.CHEM.33, 776 (1961). (83) Jasim, F., Magce, R. J., Wilson, C. L., Mikrochzna. Acta 1960, 721-8. (84) Jasim, F., Magee, R. J., Wilson, C. L., Talanta 2, 93-5 (1959). (85) Jungreis, E., Gedalia, I., Mikrochim. Acta 1960. 145-9. (86) Jungrek, E. Acta 25
(116) McCloskey, J. A,, A N ~ L CHEY. . 33. 1842 (1961). (117j McCown, J. J., Larsen, R. P., Ibid., 32, 597 (1960). (118) Ibid., 33, 1003 (1961). (119) McCurdy, W. H., Jr., Guilbault, G. G., Ibzd., 32, 647 (1960). (120) Maeck, W. J., Booman, G. L., Elliott, >‘I.C., Rein, J. E., Ibzd., 32, 605 (1960). (121) Maeck, W. J., K U S S ~hl. , E., Booman, G. L., Rein, J. E., Ibzd., 33, 998 (1961). (122) Maeck, W. J., Kussy, N. E., Rein, J. E., Ibid., 33, 237 (1961). (123) Majumdar, S. K., De, A. K., h A L . CHEM. 33, 297 (1961). (124) Malissa, H., Ottendorfer, L. J., Anal. Chzm. Acta 25, 461-2 (1961). (125) Malmstadt, H. V., Chambers, IT. E., Asa~.CHEW32, 225 (1960). (126) Malmstadt, H. V., Hadjiioannou, T. P., Pardue, H. L., Ibzd., 32, 1039 ( 1 win) \ - - - - I
(127) Malmstadt, H. V., Pardue, H. L., Ibid., 32, 1034 (1960). (128) Margerum, D. W., Santacana, Francisco, Zbid., 32, 1157 (1960). (129) Marshall, R. R., Ibzd., 32, 960 (1R6O’i. \ - - - - I .
(87) Juve
(130) Mattenheimer, H., Borner, K., Mikrochim. Acta 1959, 916-21. (131) Matuszek, J. M., Jr., Sugihara, T. T., ANAL.CHEM.33, 35 (1961). (132) Maurmever., R.., Microchem. J . 3. 333-41 (1956). (133) laid., Ibid., 4, 307-20 (1960). (134) Mavrodineanu, R., Appl. Spectrosc o p y 13, 132-9 (1959). (135) Ibid., pp. 149-55. (136) Zbid., 14, 17-23 (1960). (137) Meites, L., Anal. Chim. Acta 20, 456-62 (1959). (138) bfenzies, A. C., A N ~ LCHEW . 32, 898-904 (1960). (139) Mitchell, R. F., Ibid., 32,326 (1960). (140) Monnier., D.., Chimia 13. 314-21 ‘ (19591. (141) hioore, F. L., ANAL. CHEM. 33, 748 (1961). (1421 Morachevskil. V.. ZaItsev. V. Ii.. ~
(90) Keyworth, D. :4., Talunta 2, 383-4 (1959). (91) Kissa, E., Microchem. J . 4, 89-95 (1960). (92) Knffek, M., Provaznik, J., Chem. ltsty 55, 389-99 (1961). (93) Korenman. I. M.. Barvshnikova. ‘ kf. N., Trudy Khim. K h i k Tekhnol: 1959, 385-92. (94) Korenman, I. M., Ganichev, P. A, Ibid., 1958, 397-9. (95) Korenman, I. M., Ganichev, P. A., Gur’ev, I. A.,Zbid., 1959,397-400. (96) Korenman, I. M., Ganichev, P. A., Slepneva, A. T., Zbid., 1959, 401-5. (97) Korenman, I. M., Ganina, T.’. G., Zbid., 1958, 545-51. (98) .Korenman, I. M., Kurina, K. V., Ibzd., 1958, 573-7. (99) Korenman, I. M., Sheyanova, F. R., Shapkin, G. A,, Ibid., 1959, 393-6. (100)Kudo, Kiyoshi, J . Chem. SOC. Japan, Pure Chem. Sect. 81, 570-2 (1960). (101) Kuznetsov, V. I., .4kimova, T. G., Radiokhimiya 2, 357-63 (1960). (102) Kuznetsov, V. I., Bol’shakova, L. I., Zhur. Anal. Khim. 15, 523-7 (1960). (103) Kuznetsov, V. K., Tananaev, N. A., Trudy Ural’sk. Politekh. Inst. 1960,
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ANALYTICAL CHEMISTRY
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Uchenye Zapishi ’Leningrad. Gosudarst: Univ. 1961, 77-80. (143) MorachevsklI, Yu. V., ZaItsev, V. P.. Fokin. V. V.. Zbid.. 1960. 81-4. (144) Mottola, H: A., ’Sandell, E. B., Anal. Chim. Acta 24, 301-6 (1961). (145) Mukherji, -1.K., Mikrochim. Acta ’
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(160) Rimshaw, S. J., Malling, G. F., Zbid., 33, 751 (1961). (161) Robinson, J. K., ~ A L CHmf. . 33, 1067 (1961). (162) Robinson, J. W., Anal. Chim. Acta 23, 479-87 (1960). (163) Zbid., 24, 254-62 (1961). (164) Ibid., pp. 451-5. (165) Rolf, R. F., -4x.4~.CHEM.33, 125 i1961). (166) Ropp, R. C., Shearer, S . R., Ibid., 33, 1240 (1961). (167) Ross, H. H., Hahn, R. B., Talanta 7 , 276-80 (1961). (168) Ross, W. J.. White, J. C.. ASAL. CHERT. 33, 421 (19611. (169) Ibzd., p. 424. (170) Rudnev, K. A, Maloleeva, G. I., Rasskaxova, I-.S.,ZaLodskaya Lab. 27, 20-1 (1961). (171) Sant, B. R., Mukherji. -1.K., Anal. Chzm. Acta 20, 124-7 (1959). (172) Sanz, M. C , Chzmza 13, 192-202 (1959). (173) Schubert, J., Anderegg, G., Schwarzenbach, G., Helv. Chzm. Acta 43,410-13 (1960). (174) Schulek, E., Laszlovszky, J , V z k r o chzm. Acta 1960. 485-501. (175) Schwarzenbach, G., ASAL. CHEK 32. 6-8 - - (1960). - - I
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(204) Wallach, D. F. H., Surgenor, D. M., Soderberg, J., Delano, E., ANAL. CHEM.31, 456-60 (1959). (205) Watts, H. L., Ibid., 32, 1189-90 (1960). (206) Weiss, H. V., Lai, Ming G., ANAL. CHEW32, 475-8 (1960). (207) Weisz, H., "Microanalysis by the Ring Oven Technique," Pergamon Press, 1961. (208) Weisz, H., Mzkrochinz. Acta 1960, 703-5. (209) Weisz, H.,West, P. IT7., Mtkrochim. Acta 1960, 584-5. (210) Wenger, P. E., KapBtanidis, I., Janstein, W. von, JILkrochim. Acta 1960, 961-6.
(211) West, P. W., ~ A L CHEY. . 32, 71-9 (1960). (212) West, P.W., Diffee, J., Anal. Chim. Acta 25, 399-402 (1961). (213) West, P. W., Lorica, A. S., Anal. Chem. Acta 25, 28-33 (1961). (214) West, P. W., Weisz, Herbert, Gaeke, G. C., Lyles, George, ANAL. CHEM.32. 943 (1960). (215) West,' T. S:,Anhl. Chim. Acta 25, 301-12 (1961). (216) Ibid., pp. 405-21. (217) Weisenberger, E., Mikrochim. Acta 1960, 946-60. (218) Will, Fritz, 111, ASAL. CHEM.33, 1360 (1961).
(219) JTilliams, J. P., Microchem. J . 4 187-93 (1960). (220) Willis, J. B., ANAL.CHEM.33, 556 (1961). (221) Wilson, A. L., ilnalyst 86, 72-4 (1961). (222) YatsimirskiI, K. B., Chen. listy 54, 795-805 (1960). (223) Young, J. P., White, J. C., Ball, R. B., ANAL. CHEW32,928 (1960). (224) Ziegelhoffer, A, Hubka, M., Foglsinger, G., Chem. Zvesti 15, 158-60 (1961). (225) Zolotavin, V. L., Sannikov, Yu. I., T r u d y liral'sk. Politekh. Inst. 1959,
228-33.
Review of Fundamental Developments in Analysis
Organic Microchemistry T.
S. M A and MILTON GUTTERSON
Department of Chemisfry, Brooklyn College, Cify Universify o f New York, Brooklyn 7 0, N. Y.
T
review follows the last one (196) published without any duplication of references. It covers the original contributions in microdeterminations of the elements and functional groups that came to the attention of the authors during the period from October 1959 through September 1961. d s in the past, microdeterininations of physical constants and qualitative organic microanalysis are not included. The rei~iewprepared by Cheronis (60) is recommended to those who are interested in the latter topic. Weinstein and Wanless ( S l y ) , and Kiberly and Drake (380) have surveyed the recent developments in physical constant measurements. Since complete elemental analysis of a n organic substance became possible after the perfection of micromethods for determining oxygen and fluorine, the attention of tlie research workers in quantitative organic mic7roanalysis has been directed to the simultaneous determination of several elements with one sample, extension of functional group micromethods, rapid procedures and automatic operations, as me11 as quantitative analysis bflow the milligram scale. This is in line with the new concept of microchemistry which is concerned ith the principles and methods of chemical ehperimentation using the minimum quantity of material t o get the maximum amount of chemical information. HIS
ELEMENTAL ANALYSIS
Carbon and Hydrogen. Dorfman and Robertson (66) described modifications t o their previously published semi-
automatic procedure. The movable furnace was automatically controlled and nitrogen oxides were absorbed by manganese dioxide. The time for a determination was reduced to 15 minutes. T'ecera, Vojtech, and Synek (321) used automatic combustion with stepwise switching on of combustion zones in the presence of cobalto-cobaltic oxide as catalyst t o reduce the time to 3 to 8 minutes. Marzadro (209) combusted the sample in a short tube a t 690" C. using a cobalto-cobaltic catalyst with the oxides of nitrogen absorbed in a Pregl-type absorption tube. Arventiev, Leonte, and Offenberg (10) proposed short tube combustion in a rapid current of air and passed the vapors over a catalyst of 20% cobalto-cobaltic oxide on asbestos at 650" to 700" C. Kuck, Berry, and Barnum (184) described a n improved microcombustion furnace. The heating element \vas made of Kanthal wire and the ceramic material was constructed from commercial cordierite (magnesium aluminum silicate) lined with 0.003inch platinum foil. Stuck (290)has modified a previously described procedure employing a titrimetric finish for the determination of carbon, reducing the time t o 10 to 15 minutes. Greenfield (99) used I'regl combustion with the absorption tube replaced by a conductimetric cell for carbon determinations on 1-mg. samples. Gel'man and Van (91) employed the conductimetric method for both carbon and hydrogen using Pregl combustion. The water evolved mas reduced t o carbon monoxide over platinum and carbon black and thence to carbon dioxide over copper oxide.
Gas chromatography has been utilized for C-H determinations. Dusmalt and Brandt (68) and Sundberg and Maresh (293) converted the water formed in the combustion of the sample into acetylene with calcium carbide and determined the carbon dioxide and acetylene by thermal conductivity measurements. Vogel and Quattrone ($14) passed the carbon dioxide and water vapors directly into the chromatographic system for measurement. The accuracy for carbon was not as satisfactory as by the Pregl method while for hydrogen it was better. Cacace, Cipollini, and Perez (4.2) continuously oxidized gas chromatographic effluents over copper oxide, then converted the water to hydrogen gas using finely divided iron, and finally obtained the area under the carbon dioxide and hydrogen peaks with a n auxiliary column. Juvet and Chiu (140) employed closed flask combustion for the deterniination of carbon, using standard sodium hydroxide solution as absorbent, and back titrating the excess n-ith standard 0 . W acid. Cheng and Smullin (49) modified the method by using barium chloride solution to precipitate the carbon dioxide. The precipitate was dissolved in standard acid solution which was back titrated with standard base. Kainz and Horm.titsch (144-147) in a series of papers studied the factors affecting the oxidizing efficiency of tube fillings, their capacity, the use of mixed catalysts, and the deactivation which occurred on heating with oxygen. Probably the best catalyst is a copper oxide-cobalto-cobaltic oxide combinaVOL. 34, NO. 5, APRIL 1962
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