Functional Group Analysis Walter 1.Smith, Jr., and John M. Patterson Department of Chemistry, University of Kentucky, Lexington, Ky. 4 0506
The analytical methods discussed in this review have been selected from the literature which has become available to the reviewers from December 1971 through November 1973. As in the previous review, many straightforward gas chromatographic methods have been omitted. Of general interest are references t o microanalysis ( I S ) , atomic absorption spectrometry (39), and ultraviolet spectrophotometry (73). The reader who is seeking a new approach to a n analytical problem will be stimulated by a new book which approaches organic analytical chemistry from the viewpoint of reaction mechanisms ( 17 ) . Acids. When a carboxylic acid (10 mg) is mixed with sulfur (2-3 grams) and heated a t 1000-1100" for 10 minutes, carbon dioxide is produced from the carboxyl group, carbon disulfide from other carbons, hydrogen sulfide from hydrogen, and nitrogen gas from the nitrogen of the sample. The yields of volatiles from each source are not quantitative, but the gases obtained can be analyzed by gas chromatography and the ratio of peak areas can be compared to those obtained from glycine. In this way, satisfactory analyses of several aliphatic and aromatic acids were obtained, but pyridine carboxylic acids gave poor results (41). Volatile acids (formic-pentanoic acids) have been determined by diffusion from a sample acidified with sulfuric acid to filter paper moistened with a known amount of alkali solution placed in the cover of a Petri dish. After a suitable diffusion time (7 hours a t 20" for acetic acid, 25 minutes at 60" for butanoic acid), the excess alkali on the paper is titrated with standard sulfuric acid (26). Automatic radiofrequency titration has been used for the determination of mono- and dicarboxylic acids and phenols. The solvent is 5:8: 12 acetone: tert-butyl alcohol: toluene and the titrant is 0.1M tetra(tert-buty1)ammonium hydroxide in 9: 1 toluene:methanol(82). Carboxylic acids in air can be absorbed by ethylene glycol on porous plate absorbers, esterified by addition of sulfuric acid, and then determined colorimetrically after reaction with hydroxylamine and ferric chloride (87). In the above procedure, it was necessary to convert acid to ester in order to get conversion to the hydroxamic acid. Some recent work shows that free carboxylic acids will react directly with hydroxylamine if a Ni(I1) catalyst is used (19).The catalyzed reaction provides the basis for an initial rate assay for aliphatic acids in 10-4-10-1M solutions. In a novel application of NMR spectrometry, acids are carefully neutralized with tetramethylammonium hydroxide and the NMR spectrum of the resulting salt provides useful information about the acid (22).It is not necessary to know the exact amount of acid or base used as long as the neutralization is done carefully. This can usually be done using a visual indicator. Formic acid can be determined by flame ionization gas chromatography after isolation from solution by ion exchange and esterification with ethyl sulfate (81). Using thermal conductivity detectors, mixtures of carbon monoxide, carbon dioxide, formic acid, hydrogen, and water have been analyzed by using three parallel gas chromatography columns: 4% Ethofat and 2% isophthalic acid on Chromosorb T for formic acid, carbon monoxide, and water; Molecular Sieve 5A for hydrogen and carbon monoxide; and silica gel for carbon dioxide (33). Mono- and polycarboxylic acids can be determined by a thermometric titration in acrylonitrile, using tetrabutylammonium hydroxide, potassium hydroxide, potassium tert-butoxide, or butyllithium as the titrant. At the end point, the excess titrant catalyzes the polymerization of 394R
*
the acrylonitrile, causing a sharp increase in temperature (37). Acid Anhydrides. Several common anhydrides have been determined in the presence of their parent acids by reaction with an excess of morpholine in methanol, followed by thermometric titration of the excess morpholine with hydrogen chloride in methanol (8). Glutaric and succinic anhydrides can be determined in the presence of their monomethyl esters by utilizing the linear absorbance a t 1806 and 1859 c m - l ( 3 ) . Acid Halides. An extensive review of this subject has recently appeared (107). Active Hydrogen. Chemical ionization mass spectrometry, a n increasingly useful technique in organic chemistry, has been applied to the determination of hydrogen bonded to the heteroatoms in' alcohols, phenols, carboxylic acids, amines, amides, and thiols. The reagent gas is D20 a t 0.4 m m Hg (46).This method will prove extremely useful in laboratories equipped with the necessary equipment. In a modification of the Zerewitinoff method, the methane obtained by reaction of the sample with methylmagnesium iodide in butyl ether is determined by gas chromatography (47). In methods using lithium aluminum hydride for determination of active hydrogen, the liberated hydrogen is determined by gas chromatography (nitrogen carrier gas, charcoal, and Molecular Sieve column) (61, 86) or by combustion to water which is then determined by automatically controlled electrolysis (2). Compounds such as water, acids, alcohols, phenols, thiols, and dialkylamines liberate ethane from triethylborane when the reaction is carried out in the presence of catalytic amounts of pivalic acid or its dialkylboryl ester at 50-60". The liberated ethane is measured volumetrical1Y (53). Alcohols. A comprehensive review on the determination of hydroxyl groups has recently appeared (102). Tertiary alcohols are readily dehydrated by a 20% solution of sulfur dioxide in dioxane at, 10". The resulting water can then be titrated with the Karl Fischer reagent. Tertiary alcohols in the presence of hydroperoxides can be determined on the basis of the difference in the amount of water formed a t 10" as above and the amount formed in 20 minutes a t 70". At 70°, the water formed is a measure of both the alcohol and the hydroperoxide (91). In another application of the Karl Fischer reagent, the reagent is used to titrate the water formed by esterification of the 5- to 10-mg sample with trifluoroacetic acid in a sealed tube. Many simple alcohols give good results but sugars give results which are lower than the theoretical (52). By adding tris(dipiva1omethanato)europium to solutions of lower molecular weight alcohols, the chemical shifts of the carbon-bonded protons are better resolved, thus permitting analysis of certain mixtures of alcohols by NMR spectrometry. The method has been demonstrated for mixtures such as 1-, 2-, and 3-pentanols; 2-methyl-1-butano1 and 2-methyl-2-butanol; and 1-hexanol and l-heptanol. Data given in this reference should be consulted for possible analysis of other alcohol mixtures (79). Aldehydes a n d Ketones. Aromatic aldehydes have been determined with i l % relative error by reaction with a n excess of 2,4-dinitrophenylhydrazinefollowed by thermometric titration of the unreacted hydrazine with a standard solution of o-methoxybenzaldehyde in 1:1:23 sulfuric acid:water:isobutyl alcohol ( 7 ) . A micromethod for the carbonyl group utilizes oximation in a sealed tube in the presence of pyridine or ethyl-
A N A L Y T I C A L CHEMISTRY, VOL. 46, NO. 5, APRIL 1974
Walter T. Smlth, Jr., professor in the Chemistry Department at the University of Kentucky. Lexington, has had industrial experience with Mailinckrodt Chemical Works and Ethyl Corp. Before joining the Kentucky faculty, he taught at State University of Iowa. His education was obtained at the University of Illinois and Indiana University. He was a Lilly Fellow at Indiana in 1944-46 and a Fels Fund postdoctoral Fellow at Chicago in 1946-47. He is author or coauthor of several publications in scientific journals. Durina 1963-64 he was visitino Professor a i d chairman of the Department of Chemistry at the Universit Y O f Libya, Tripoli, and in 1965-66 was a Fulbright-Hays visiting professor at the American University of Beirut, Lebanon.
John M. Patterson, professor in the Department of Chemistry at the University of Kentucky, received a PhD from Northwestern University in 1953, after taking undergraduate work at Virginia Military Institute and Wheaton College. His fields of interest include investigations of high-temperature reactions, nitroparaffin chemistry, heterocyclic compounds, and photochemical reactions in solution.
ene glycol and subsequent Karl Fischer titration of the water formed (84, 85). Methyl ketones react with o-nitrobenzaldehyde in the presence of base to form indigo. Indoxyl is a fluorescent intermediate in this reaction, and the rate of its formation Drovides the basis for a fluorometric determination of methyl ketones ( 5 4 ) . A raDid method for ketones (5-25 X 10-5Mis based on the ratk of reaction of the ketone with p-dimethylaminobenzaldehyde. The rate is followed by measuring the absorbance of the a$-unsaturated carbonyl compound formed (97). The method appears to be limited to ketones having an alpha methyl or methylene group. Amines. A wide variety of amines, as well as basic amides and basic sulfur and phosphorus compounds can be determined by a thermometric titration with perchloric acid in a-methylstyrene or with boron trifluoride in isobutyl vinyl ether. At the end point, the excess titrant catalyzes the polymerization of the solvent, causing a sharp increase in temperature (36, 38). Relative standard deviation is around 1%. Acetone is a suitable solvent for the titration of amines with perchloric acid in dioxane. The end point can be determined with methyl violet indicator or potentiometrically. Binary mixtures of aliphatic and aromatic amines can be determined by sequential potentiometric titration (29). 2-Nitrobenzenesulfenyl chloride may be a useful new reagent for determination of primary and secondary amines (67). An excess of reagent is used and the excess is titrated iodometrically. Alcohols and phenols do not interfere. A new reagent for fluorometric determination of primary amines, amino acids, and peptides is 4-phenylspiro[furan-2(3H),l’-phthalan]-3,3’-dione.A synthesis of the reagent has been described (106). In a modification of the Van Slyke method for primary amino groups, the reaction chamber is connected to a gas chromatograph and the nitrogen liberated is determined from the peak area (70). Various bases can be carefully neutralized with methanesulfonic acid or 2,4,6-trinitrobenzenesulfonic acid, using a colored indicator, and the resulting salt can be characterized by NMR spectrometry (22). The use of near-infrared spectroscopy for determination of primary and secondary aliphatic amines has been extended to cover samples containing greater than 10% nitrile content (95). 2-Nitrobenzensulfenyl thiocyanate has been used for determination of amines, amine salts, and amino acids. After reaction of the sample with the reagent in dioxane in the presence of alkali metals, the excess reagent is decomposed with aqueous base. The iodine liberated upon addition of potassium iodide and acid is titrated with standard thiosulfate (68). Primary and secondary amines are converted to their 2,4-dinitrophenyl derivatives and then extracted into nitromethane and determined by the color reaction with potassium borohydride. Absorbances a t 580-610 n m follow Beer’s law for microgram amounts of sample (10). 9-Isothiocyanatoacridine and primary or secondary amines can be converted to a cyclized product whose fluo-
rescence can be taken as a measure of the amount of primary or secondary amine present (23). Amino Acids. For the rapid determination of microgram amounts of taurine or cysteic acid in the presence of large amounts of other amino acids, the sample is converted to dinitrophenyl derivatives and extracted with chloroform to leave a n aqueous solution containing only N-(2,4-dinitrophenyl)taurineor N-(2,4-dinitrophenyl)cysteic acid. The latter compounds can then be determined by absorbance measurements (112). N-Trimethylsilyl- 0-n-butyl esters of 20 amino acids are separated in 35 minutes by gas chromatography on a 0.2% OV-7/GLC-110 textured glass bead column (42). Spectrophotometric and oxidative methods for amino acids are based on the reaction of the amino acids with peri-naphthindan-2,3,4-trione hydrate a t p H 2.5 to give a red precipitate of dihydroxy-peri-naphthindenone. The red product can be dissolved and determined either spectrophotometrically at 342 nm or by titration with iodine or N-bromosuccinimide ( 5 ) .Determination of amino acids on a picomole scale has been accomplished by reaction with pyridoxal followed by reduction with NaBH4 and fluorometric measurements of the pyridoxylamino acids after separation by liquid chromatography on a cation exchanger (57, 60). Reduction with NaBT4 provides for sensitive radioactive measurement. A 1:5 mixture of acetic acid and acetonitrile has been recommended as a solvent for differential titration of a mixture of amino acids (56). Some of the procedures described in the section on amines are also applicable to amino acids. Aromatic Hydrocarbons. A representative sampling of the simpler aromatic compounds has been determined by first converting them to phenols which can be determined colorimetrically (with 4-aminoantipyrine and ferricyanide). Despite the fact t h a t the hydroxylation reaction using ferric ion, hydrogen peroxide, and catechol is far from quantitative and tends to dihydroxylate, the reaction conditions have been worked out so that reproducible results are obtained. It is necessary to use a calibration curve appropriate to the aromatic compound being studied, but a variety of compounds varying from anisole to nitrobenzene give satisfactory results. The tendency of the reagent to introduce a second hydroxyl group is hindered by the addition of a cyclodextrin (18). Azides. The determination and characterization of organic azides has been reviewed (40). Carbohydrates. Several ketoses (fructose, sorbose, tagatose, mannoheptulose, and sedoheptulose) are converted to ultraviolet-absorbing materials by 4N hydrochloric acid a t 80” and can be determined by measuring the absorbance a t the proper wavelength. The length of heating required varies greatly, depending on which ketose is used. Ribose, and probably other aldopentoses, interfere but aldohexoses, 6-deoxyhexoses, 2-deoxy-~-glucose,D-glucoheptose, and sugar alcohols do not (76). Epoxides. In an earlier method for determining ethylene oxide, the epoxide is cleaved by sulfuric acid to give glycols which are in turn cleaved with excess H5106 (20). In a new version, applicable to nanomole quantities of a variety of epoxides, 50% glyme is used as solvent and the
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same general procedure is followed up to determination of the excess H510s. I n the new method, the excess H5IOs reacts with cadmium iodide to generate free iodine which is then determined photometrically as its colored complex with starch (63). In another method, the epoxide is cleaved in a standard solution of hydrogen chloride in dimethylformamide and the excess chloride is titrated turbidimetrically with silver nitrate ( 1 ) . Esters. In a variation on the classical saponification procedure, esters are hydrolyzed in 30-120 minutes a t 80" in an aqueous solution of triethylamine (45 grams/l.) and the excess amine is titrated with hydrochloric acid. The method gives recoveries of 98.9-101.0% with esters such as vinyl acetate, ethyl acetoacetate, phenyl salicylate, and trihaloacetates (104). Methyl ester groups in poly(ethy1ene terephthalate) have been determined by hydrazinolysis of the sample followed by gas chromatographic determination of the methanol liberated (114). In a somewhat related procedure, simple esters (10-50 mg) are hydrolyzed a t 37", the liberated alcohol is collected a t O", and determined by gas chromatography (30). The analysis of triglycerides is the subject of a recent book (58). Ethers. In the determination of alkoxy1 groups by gas chromatography of the alkyl iodides resulting from hydrogen iodide treatment of the sample, use of a smaller reaction vessel and no more than a 100% excess of hydrogen iodide eliminates the problem resulting from hydrogen iodide volatilizing along with the alkyl iodide (16). The general idea of hydrogen iodide cleavage followed by gas chromatography has been applied to the determination of methoxyl groups in water-soluble components of peats and soils (64). Hydroxylamines. In a study of the use of iodine to oxidize substituted hydroxylamines to nitrite, only methylhydroxylamine gave quantitative results (100). Nitrate Esters. The N=O asymmetric stretching band is the basis for an infrared spectral determination of ethyl nitrate, amyl nitrate, ethylene glycol dinitrate, glycerol trinitrate, and cellulose nitrate. Chloroform and tetrahydrofuran are suitable solvents and Beer's law is followed (14). Nitriles. Both nitriles and hydrogen cyanide are converted to ammonia by the Radziszewski reaction (30% hydrogen peroxide) followed by alkaline hydrolysis, and total hydrolyzable nitrogen in mixtures of nitriles and cyanide can be determined in this way (110). The technique of alkali fusion followed by gas chromatography (27) has been used with satisfactory results for the determination of nitriles, amides, and urea derivatives. The amines or ammonia liberated during the fusion are determined on a Chromosorb 103 column (28). The technique is especially valuable for polymeric materials which are highly resistant to hydrolysis. Nitro Compounds. Several aromatic nitro compounds have been determined by reduction with lithium aluminum hydride in tetrahydrofuran, followed by measurement of the absorbance of the resulting azo compound. The absorbance maximum varies with the nature of the sample from 350-375 nm (99). 2,4-Dinitrotoluene and 2,6-dinitrotoluene were estimated in an o-nitrotoluene nitration product on the basis of their infrared absorption (carbon tetrachloride solvent) a t 914 and 892 c m - l respectively (12). For microgram amounts of aliphatic and aromatic nitro compounds, the sample is used to oxidize ferrous ion (under nitrogen) to ferric ion which is then determined photometrically at 470 nm as the thiocyanate complex. Nitrobenzene gave low results, but a variety of other compounds were determined satisfactorily ( 9 ) . Nitrosamines. Denitrosation of nonvolatile nitrosamines and nitrosamides by thionyl chloride in methylene chloride gives nitrosyl chloride. This latter compound can be volatilized in a stream of nitrogen, trapped in alkali, and determined as nitrite ion (59). Nitramines and nitramides do not interfere. Organometallic Compounds. A relatively rapid procedure for the determination of alkylaluminum compounds involves titration with pyridine using a phenazine indica396R
tor (50).The reactions occurring during this titration have been investigated recently and have been found to be complex but quantitative (44). Dioxane complexes of phenylcalcium and rn-tolycalcium iodides can be analyzed by an initial water hydrolysis followed by gas chromatography of the benzene and toluene produced (15). Tetrahydrofuran solutions of diphenylcalcium can be analyzed in the same way. A direct titration procedure has been developed for the determination of butyllithium in hexane-ether mixtures. A 2-butanol titrant and a 2,2'-bisquinoline indicator were used a t -78" (25). A fast and reliable determination of alkyllead mixtures in gasoline utilizes a gas chromatographic separation of the alkyllead compounds followed by flame photometry (65). The method is applicable over the concentration range of 1ppb to 1000 ppm. Methods available for the determination of organotin compounds have been reviewed recently (24). The polarographic behavior of trialkyltin halides, hydroxides, and carboxylates has been investigated in Britton-Robinson buffer and in NaOH solutions (88).Polarography represents a potential method for the determination of these compounds in sewage and polymers. A photometric titration of trialkyltin(1V) compounds using dithizone and a chlorobenzene solvent is sensitive to 0.003 mg in the analysis of triethyltin oxide. The trialkyltin compounds are first extracted by chlorobenzene from NaOH-EDTA or NaCN solutions and then titrated (105). Peroxides. An infrared method for difuroyl peroxide is based on the absorbance a t 1765 c m - l . Beer's law is followed if the base line is drawn between the points at 1869 and 1628 cm - (89). Phenols. For expert opinions regarding useful procedures for phenol determinations, the recent report of an IUPAC commission should be consulted (71). Among the colorimetric methods recommended are those using ferric chloride ( l o g ) , ferric ferricyanide (74), or Millon's reagent (51, 62, 77, 78) as reagents, and those depending on the formation of a quinone imine derived from either 2,6-dibromo-4-chloroimine quinone (92), aniline and hypochlorite (48, 72), 4-aminoantipyrine (49), or 4-dimethylaminoantipyrine ( 75). The coupling of diazotized 2-aminobenzothiazole with phenols is recommended as a widely applicable method ( 11 ) . Diazotized sulfanilic acid and p-phenylazoaniline are reported to be particularly useful coupling reagents for colorimetric determination of phenols ( 1 1 1 ) . For bromometric titrations of phenols (potentiometric end point), propylene carbonate is a useful solvent (55). Methods for determining total phenols and individual phenols in mixtures have been reviewed recently (98). For determination of p-substituted phenols, the sample is treated with acidified sodium cobaltinitrite and the resulting 2-nitro-p-substituted phenol is extracted into chloroform and its absorbance is measured at 366 nm. Beer's to 5 X law is followed for solutions that are 5 X 1 0 - 4 (93). ~ Separate determination of the two phenolic groups of bisphenols is possible by titration with tetrabutylammonium hydroxide in methyl sulfoxide (56). Q u a r t e r n a r y Ammonium Salts. Several quaternary ammonium iodides have been determined by measuring by gas chromatography the methyl iodide formed on pyrolysis. Salts other than iodides are first converted to iodides (103). Silicon Compounds. The oxidation of the Si-H bond in methylhydridopolysiloxanes with N-bromosuccinimide is the basis of a determination of the Si-H linkage in these polymers (43). The excess N-bromosuccinimide is treated with KI and the liberated iodine titrated with NazSz03. Thiols. A comparative study of five methods for the analysis of thiols showed (108) that the most reliable and reproducible procedure involved a potentiometric titration of the iodide liberated on reaction of the thiol with iodoacetate. A silver-silver iodide electrode was used. Cysteinyl groups in peptide residues can be titrated quantitatively and rapidly with 2-fluoro-3-nitropyridine. The end point is detected by observing the circular dichroic absorption at 367 nm (101). An indirect method has been developed for the determi-
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nation of thiol in low molecular weight compounds and protein material ( 4 5 ) . The sample is digested with excess thiol reagent (AgN03, N-ethylmaleimide, or p-chloromercuribenzoate) and then the excess reacted with excess gluthathione. The unreacted glutathione is titrated with AgN03 amperometrically. Thiol groups in cysteine, cysteine ethyl ester, and 3-mercaptopropionic acid cannot be determined by this method when AgN03 is the thiol reagent because of complex formation. N-Ethylmaleimide was suitable for the analysis of these compounds. Thiols can be titrated with Hg(C104)~using a bromide ion-selective electrode (83). Acetone is the preferred solvent. The heterocyclic disulfides, 6,6'-dithiodinicotinic acid, 2,2'-dithiodipyrimidine, 6,6'-dithiodinicotinamide, and 2,2'-dithiobis(4-hydroxypyrimidine)have been used to determine thiols (35) by the spectrophotometric method previously described by Grassetti (34). Samples of ethanethiol in air can be analyzed by titration with sodium arsenite (starch indicator) after absorption in Cd(0H)z and treatment with an iodine-sodium azide solution (32). Thiols and H2S also react while CS2, sulfate, and sulfite do not interfere. Thiols, in dilute sulfuric acid solution, can be titrated quantitatively with NaN02 using an external starch-KI indicator (21). Disulfides do not interfere. Sulfinic acidthiol mixtures are analyzed using the titration method (which gives the total sulfinic acid-thiol content) followed by a photometric thiol determination using Folin's reagent. The sulfinic acid concentration is found by difference. The titrimetric determination of thiols- in the presence of disulfides can be accomplished by using N-bromosuccinimide and a KI-starch indicator (6). Various N-substituted maleimide derivatives have been prepared and tested as reagents for the thiol group. The N-(p-ethoxyphenyl) derivative reacted to produce an addition compound whose color was weaker than that obtained from N-ethylmaleimide (113). The use of the N (9-acridinyl) derivative permitted the detection of 0.4 X
LITERATURE CITED Aksenov, A. I . , Zavod. Lab., 37, 1437 (1971). Anisimova. G. F.. Klimova, V. A,. lzv. Akad. Nauk SSSR, Ser. Khim., 1972, 581-3. Antonenko, N. S.. Gravshenko, A. i., Zh. Anal. Khim., 27, 1224-6 (1972). Ashworth, M. R. F., "The Determination of Sulfur-containing Groups," Academic Press, New York, N.Y., 1972. Awad, N. I., Nashed, S.. Hassan, S. S. M., Zachary, R. F., Talanta, 19, 31-6 (1972). Bachhawat, J. M.. Ramegowda, N. S., Koui, A. K.. Narang, C. K.. Mathur. N. K., lndianJ. Chem., 11, 614 (1973). Bark, L. S., Bate, P.. Analyst (London), 96,881-4 (1971). lbid., 97, 783-6 (1972). Bartos, J., Analusis, 2, 41 1-2 (1973). lbid., pp 479-80. Bartos, J. Ann. Pharm. Fr., 29, 147 (1971). Bronshtein, E. A,, Kaminskii, A . Ya., Gitis. S. S., Zavod. Lab., 38, 180-1 (1972). Campbell, A . D.. lnt. Rev. Sci. Phys. Chem., Ser. One, 13, 1-42 (1973). Carignan, Y. P., Hickman, C. L., U.S. Nat. Tech. Inform. Serv., A D Rep. No. 753938 (1972). Chernoplekova, V. A.. Zemlyanichenko, M. A., Zakodynskii, K. I., Sheverdina, N. I . , Nov. Sorbenty Khromatogr., 1971, 105-7. Chumachenko. M. N., Kolesnik. L. V., lzv. Akad. Nauk SSSR, Ser. Khim., 1971, 2090-2. Connors. K. A., "Reaction Mechanisms in Organic Analytical Chemistry," Wiley, New York, N.Y., 1973. Connors, K. A., Albert, K. S.. Anal Chem., 44,879-81 (1972) Connors. K. A., Munson, J. W.. lbid., pp 336-9.
10-6Mthiol and disulfide (66). The reaction product of the reagent and thiol showed a strong fluorescence at 426 nm. Unsaturation. A micromethod provides for the addition of a known excess of N-bromosuccinimide to the sample dissolved in acetic acid (90). The excess reagent is determined by an iodometric titration. Samples studied included stilbene, crotonic acid, cinnamaldehyde, and vinyl acetate, among others. A method applicable to micromolar quantities of alkenes depends on the linear relation between the amount of alkene present and the heat envolved when the sample is hydrogenated over palladium-on-charcoal a t slightly over 2 atmospheres. The relative standard deviation is 1-370 (80).
An apparatus and procedure have been described for determining simple alkenes by passing a standard mixture of oxygen and ozone a t constant rate through the sample. The time taken to decolorize an internal indicator is a measure of the amount of unsaturation present in the sample. The procedure should be most useful where large numbers of samples are to be analyzed. The method is subject to the limitations common other methods based on ozone reactions (94). For the determination of alkenes in the presence of alkanes, the alkenes are converted to alcohols by the hydroboration-hydrogen peroxide oxidation, and the mixture is then analyzed by gas chromatography. The ratio of cu-olefins to inner olefins can be determined from the ratio of terminal (primary) alcohols to nonterminal alcohols (69). Miscellaneous Sulfur Compounds. A monograph describing the analysis of sulfones, sulfoxides, sulfonyl halides, thiocyanates, isothiocyanates, and isocyanates has been published recently ( 4 ) . Excess titanium(II1) sulfate has been used to reduce sulfoxides and disulfides (31). Titration of the excess reagent with ferric alum allows an analysis of these compounds. A combination of total sulfur and infrared absorption methods has been applied to the determination of 1,2-epithioalkanes (96).
PO) Critchfield, F. E., Johnson, J. B., ibid., 29, 797-800 (1957). (21) Danehy, J. P., Eiia. V. J., ibid., 44, 1281-4 (1972). ( 2 2 ) Degani. Y., Patchornik, A.. ibid., pp 21705. (23) DeLeenheer. A., Sinsheimer, J. E.. Burckhalter. J. H., J. Pharm. Sci.. 62, 1370-1 (1973). (24) Diliard, C. R., "Organotin Compounds." voi. 3. A. K. Sawver. Ed., Dekker. New York. N.Y., 1972, pp997-1006. (25) Ellison, R. A,, Griffin, R., Kotsonis, F. N., J. Organometal. Chem., 36, 209-13 (1972), (26) Fedoseev, P. M., Mironova, L. A,, Osadchii, V. D., Zavod. Lab., 38, 655 (1972). (27) Frankoski, S. P.. Siggia, S., Anal. Chem., 44, 507 (1972). (28) lbld., pp 2078-80. (29) Fritz, J. S., Burgett. C. A,, ibid., pp 16734. (30) Garavelli, C. B., J. Tenn. Acad. Sci., 47, 89-90 (1972). (31) Gawargious, Y. A,, J. Phys. C, 4, 673-82 (1971), (32) Gershkovich, E. E., Gig. Tr. Prof. Zabol., 15, 58-9 (1971). (33) Goltz, H. L., Moffat, J. B., J. Chromatogr. Sci., 9, 546-50 (1971). (34) Grassetti, D. R., U.S. Patent 3,597,160, Aug. 3, 1971, Appl. Apr. 2 , 1969. (35) Grassetti, D. R.. Murray, J. F., Jr., U S . Patent. 3,698,866, Oct. 17, 1972, Appl. 777.005. Nov. 19, 1968. (36) Greenhow. E. J., Spencer, L. E., Analyst (London), 98,8 1-9 (1973), (37) lbid., pp 90-7. (38) lbid., pp 98-102. (39) Gupta, H. K. L., Boltz, D. L.. Microchem. J., 16,571-6 (1971). (40) Gurst, J. E., in "Chemistry of the Azido Group." S. Patai, Ed.. Interscience, London, 1969.
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Ion Exchange Harold F. Walton Department of Chemistry, University of Colorado, Boulder, Colo. 80302 This Review was prepared in the same way as the 1972 review of ion exchange. References were correlated with those cited in 1972 to avoid repetition. Analytical Abstracts were scanned through November 1973; Chemical Abstracts through December. To decide whether to include a paper in this Review we asked, "Does it concern the analytical use of ion-exchanging materials?" A paper on liquid chromatography, for example, was examined to see what material was used as the stationary phase. If it was an ion-exchange resin, the paper was included in the review. If it was porous silica or an unsubstituted styrene-divinylbenzene polymer, the paper was not included. This distinction is unfortunate for the reader of this review who seeks a method that will work for his compounds, and does not particularly care whether it uses an ion exchanger or not. This reader will, of course, consult the review on Chromatography, but, to make things easier, we have included a few references to the general technique of high-performance liquid chromatography even though they do not specifically involve ion exchange. We have stretched the definition of ion exchange to include, for example, the use of immobilized organic chelating agents to absorb metal ions and the use of solid salts to absorb olefins. "Liquid ion exchangers" are properly considered under analytical solvent extraction, but a few key references are cited here, particularly to illustrate the use of such liquids absorbed on solid supports for column chromatography. 398R
T o keep the review within bounds, we have not tried to include every paper that mentions an analytical use of ion exchange. This would have been an impossible task, and a n unnecessary one. Ion exchange is a common laboratory process, and there is little point in citing repeated examples of its routine use. The commonest use of ion-exchange chromatography is for amino-acid analysis, and so many variations are possible with commercial amino-acid analyzers that a considerable number of papers are published on this subject. We have included many of them here, because (to judge from reprint requests) most of our readers work in biochemical and medical laboratories, but complete coverage was not attempted. In several instances, two or more papers are combined under one reference number to save space. Thus the number of papers cited is more than in 1972. Areas of increased activity include inorganic ion exchangers, selective absorbents including optically active absorbents, ion exchange of metals in mixed solvents, and, of course, high-performance column chromatography.
BOOKS, REVIEWS The book by Dorfner ( A 3 ) carries extensive compilations of commercial ion exchangers and their properties, and, as a handbook of data, should be on the desk of every chemist who works with these materials. For reviews of special aspects of ion exchange, the two volumes edited by Marinsky and Marcus ( A l l ) are recommended. Volume 4
ANALYTICAL CHEMISTRY, VOL. 46, NO. 5, A P R i L 1974
