Functional Group Analysis Walter T. Smith, Jr., and John
T
M. Patterson, Department o f Chemistry, University of Kentucky, Lexington, Ky. 40506
HE ANALYTICAL METHODS discussed in this review have been selected from the literature which has become available to the reviewers from December 1969 through Xovember 1971. A great many analyses can be performed by simply injecting the sample into a suitable gas chromatograph. I n general, we have omitted determinations of this type but we have included methods in which gas chromatography is used in an indirect or unusual way. In addition to the methods discussed under the appropriate headings which follow, several topics of a more general nature should be called to the reader's attention. These include the growing application of S M R spectrometry to quantitative analysis, particularly in such areas as determination of purity (67), analysis of diamine stereoisomers (117), and the use of a high resolution NMR spectrometer controlled by a dedicated computer (103). Other topics of note include the determination of total carbon-hydrogen bonds by near infrared analysis (137), recent develop ments in spectrophotometric determinations (89), titrimetric methods using aqueous or nonaqueous methods (110), chromic acid oxidations for the determination of nitrogen compounds (50, GO), general methods for nitrogen compounds (59), and methods for compounds with nitrogen-nitrogen linkages (39). Acids. The characteristic N M R peak due to the H-C! of formic acid provides a basis for the determination of low concentrations (0.025-0.40Q/0) of formic acid in acetic acid. The integration of the characteristic peak a t 6 8-9 ppm is calibrated against known standard solutions of formic acid in acetic acid or by use of CHCL (6 7.3-7.9) as an internal standard. This method (11) is reported to give results comparable to those obtained by the mercuric acetate method (97). Isopropyl alcohol and, in some cases, acetone are reported to be good solvents for the potentiometric titration of acetic acid and it,s various chloro and bromo deviatives (64). A variety of a-hydroxy acids has been determined satisfactorily by oxidation with cerjum(1V) sulfate followed by iodometric determination of the excess cerium(1V) sulfate (102). Salicylic acid, and its 4nitr0, 5 nitro, and 3,Minitro derivatives form 1: 1 benzene-soluble complexes with several basic dyes (Rhodamine 6G, Butyl Rhodamine, Astraphloxin FF,
Astra Violet FR3L, and Cationic Orange 3). This reaction provides the basis for a colorimetric procedure for determination of the acids (58). A solution of the acid (5 x 10-6 to 5 x 10*M, 10 ml) is mixed in a separatory funnel with 2 ml of buffer solution (pH 4-8 is best), 2 ml of dye solution (lO-aM) and 4 ml of benzene. After 5 min, the absorbacce of the benzene layer a t 555 nrn is measured. Thallium(1) ethoxide has been recommended as a new thermometric titrant because of its basicity and solubility in organic solvents (8). The reagent hzs been used for titrations of organic acids and phenols in benzene, carbon tetrachloride, chlorobenzene, and methylene chloride. In some cases, e.g., m-methoxybenzoic acid, a 2% ethyl alcohol-%% benzene solution is used to avoid precipitation. Conversion of acids, phenols, and mercaptans to their pentafluorobenzyl esters or ethers makes it possible to determine sub-nanogram amounts of these compounds by electron capture gas chromatography (53). Coulometric methods and catalytic thermometric titrations for the determination of organic acids have been compared (116). Alcohols. The use of l9F-NMR spectrometry for the analysis of trifluoroacetyl derivatives of sterols (4?'), polyols, glycosides, and terpene alcohols (48) has been reviewed. This useful technique has been applied to the determination of the relative concentrations of 2-alkanol enantiomers (66). I n this method the alcohols are converted to the trifluoroacetyl derivatives of optically active mandelates. The relative amounts of the enantiomers are then determined from the relative peak heights for the diastereoisomeric esters. Bexafluoroacetone readily forms a hemiketal with many hydroxy compounds and these derivatives can be used in I-BF-NhIR spectrometry in much the same way that the trifluoroacetyl derivatives are used (68). In a comparison of trifluoroacetic acid and hexafluoroacetone derivatives of some sterols, the trifluoroacetic acid derivatives were preferred (49). Ethyl alcohol in body fluids can be determined by enzymatic oxidation of the alcohol Rith alcohol dehydrogenase followed by spectrophotometric determination of the KAL)Hp formed (46). The method is quite sensitive and has been automated (40).
In two recent vrocedures for the determination of alcohols, acetylation with isopropenyl acetate or silylation were used to convert the alcohols to more volatile derivatives for subsequent determination by gas chromatography (125). Isopropenyl acetate is reported to react quantitatively with primary alcohols (1.5 hr) and secondary alcohols (3 hr or more). Thus, 50-100 mg of the alcohol, 100-200 mg of isopropenyl acetate, and 1-2 mg of p-toluenesulfonic acid &-ere heated a t 80 "C for the required time and 5 pLi of the reaction mixture was chromatographed on a 2-ni X 0.6-cm column containing 1 : 9 polyethylene glycol 3000 on Clhemosorb (60-80 mesh) a t 80-150 "C. Errors of 1% or less were obtained with sixteen different alcohols. The mixture of glycols (largely ethylene glycol, propylene glycol, glycerol, and hexitols) obt'ained by high pressure hydrogenolysis of sucrose is difficult to analyze because of the difficulty in removing all of the water from the mixture. h satisfactory analysis is obtained by treating the concentrated mixture, still containing water, witjh a commercial silylating reagent containing trimethylsilylimidazde in pyridine and chromatographing the silylated mixture thus obtained (119). The method is faster than acetylation processes be cause of the shorter period required for derivatization and also because of the shorter retention times for the derivatives. Alcohols which react with acrylonitrile (CI-C, primary and secondary alcohols, benzyl alcohol) have beeii determined by reaction with a known excess of acrylonitrile, followed by determination of the excess by gas chromat,ography (86). The method has also been used for hexyl, octyl, nonyl, dodecyl mercaptans, thiophenol, thiocresol, thionaphthol, and benzyl mercaptan. Tertiary alcohols do not react and the compounds listed above can be determined in their presence. The use of xenon trioxide for the determination of alcohols in very low concentration (ppb levels) has been studied and appears to offer useful possibilities (65). Higher alcohols are reported to give a violet-red color (absorbance a t 530 nm) when treated with vanillin and sulfuric acid. By use of calibration curves, this has been made into a quantitative colorimetric procedure (129). Absorption in the near infrared region is the basis for a determination of the
ANALYTICAL CHEMISTRY, VOL. 44,
NO. 5, APRIL 1972
e
207R
concentration of isopropyl alcohol in its mixtures with water (106). The absorption a t 1 . ~ 1 . 0 0 1microns is measured. The alcohol concentration must be greater than 75%. Acetone and diisopropyl ether interfere. Aldehydes and Ketones. The ilse of 2-(diphenylacetyl)-l,3-indanedione 1-hydrazone as a reagent for carbonyl compounds has been rather thoroughly investigated (94). Carbonyl compounds react readily with this reagent.
A spectropbotornetric method for the determination of n o m 1 carbonyl compounds in the presence of sugars is based on treatment of the unknown mixture with 2,44initrophenylhydrazine under controlled conditions such that only the normal carbonyl compounds react (100). A modification of the oximation method for determination of formaldehyde and acetaldehyde determines the
-R'(H)
The products are highly colored and fluorescent and can be determined by either colorimetry or fluorescence spectrometry. The methods are a p plicable to a wide variety of carbonyl compounds including steroids and other compounds of biological importance. The ultraviolet absorption of the compounds formed from barbituric acid and citral, furfuraldehyde, vanillin, salicylaldehyde, cinnamaldehyde, piperonal, and o-methoxybenzaldehyde has been used for the determination of these aldehydes (69). Aldehydes such as benzaldehyde and nonanal also react but the absorption is only about 0.01 that of the above aldehydes and they do not interfere. The Claisen condensation of ethyl oxalate with ketones containing an a-methylene or an a-methyl group gives derivatives which can be determined by their ultraviolet absorption. Thus ketones with an a-methylene group, but no a-methyl group (e.g., androst-kn5j3-ol-17-one) condense with ethyl oxalate in 9: 1 t-BuOH: cyclohexane containing t-BuONa to give a product absorbing a t 294 nm (36). When an a-methyl group is available condensation takes place a t that position. 0
I/
(CHa)zCHCH2CCHa
00
1/11 + EtOCCOEt
b=e +
OH 0
Ip I I/ (CH&CHCHzCCH=CCOEt The above product absorbs a t 286 nm. The corresponding product from p-C1-
0
II
CsH4CCHa absorbs at 319 nm (109). 208R
4
equivalence point by potentiometric means (184,185). Amides. Methods for the determination of amides (and related compounds such as amidines, imidates, imides, barbiturates, and sulfonamides) have been thoroughly covered recently (4,128). Amines. Primary aromatic amines such as aniline and benzidine have been determined by reaction with salicylaldehyde in pyridine followed by potentiometric titration of the excess mlicylaldehyde with sodium hydroxide in water-isopropyl alcohol (26). A variety of primary and secondary aliphatic amines have been determined by an amperometric method in which the amine a t pH 8.3 is titrated with hypobromite using a rotating platinum electrode. The method is claimed to be preferable to acid-base titrations for 0.01N solutions of aliphatic amines and has been applied to simple aliphatic primary and secondary amines and also to glycine, sarcosine, alanine, phenylalanine, lysine hydrochloride, and ephedrine sulfate (16). The UBB of 10-12M lithium chloride solutions has been recommended as the solvent for the potentiometric titration of amines with M HC1. Potential jumps observed are reported to be better resolved, especially for the second amino group in m- and p-phenylenediamines and diazabicyclooctane (104). Other amines titrated include o-phenylenediamine, dihydroxydiethylpiperazine, and dihydrazides of adipic and carbonic acids. A gas chromatographic method for the determination of primary and secondary amines utilizes the reaction of excess acrylonitrile with the amine,
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
followed by determination of the excess acrylonitrile by gas chromatography on a 300 X 0.6cm column packed with polyethylene glycol 3000 on Chromosorb W at 100 "C (85). Acetone and ethyl alcohol are suitable internal standards. The method is recommended for lower primary amines, cyclic amines, aliphatic diamines, and amino acids. For the determination of compounds containing both primary and secondary amino groups in the same molecule (such as diethylenetriamine, triethylenetetramine, and tetraethylenepenb amine) a high frequency titration in methyl or ethyl alcohol has been used. I n direct titration in methyl alcohol the primary amino groups are titrated before the secondary amino groups, but the reverse is true in ethyl alcohol (95). Coupling of a diazotized aromatic amine with 2,6diaminopyridine gives an azo dye which when treated with ammoniacal copper sulfate gives a highly fluorescent derivative. The spectral characteristics of this derivative (excitation maximum 360 nm and fluorescence maximum 420 nm) were found to be independent of the amine structure for the amines tested. Amines in the concentration range 2-6 ng/ml have been determined with a relative standard deviation of 6%. The amines studied were mostly substituted anilines. Amines which are difficult to diazotize would present difficulties (22). Several types of reagents have been used for forming colored compounds with amines. Bromonitrosol (3-bromo2-nitroso-1-naphthol) reacts with aromatic amines and hydrazines to give azo compounds (67). Treatment of amines with p-benzoquinone and hydrogen peroxide gives a colored product absorbing a t 480 nm (130). Primary and secondary aliphatic amines form dithiocarbamates with carbon disulfide. The reduction of tetrazolium blue to diformazan by the dithiocarbamates can then be used for a colorimetric determination of the amines in 0.01-mg amounts (7). Arylamines (and also phenols) undergo oxidative coupling N,N-dimethyl-p-phenylenediwith amine. The oxidizing agent is K3Fe(CN)B-Na&r207. The method is sensitive and can be used with lo6 to 10-5 molar solution (62). The oxidation has also been accomplished with a peroxide-peroxidase system (51). Extractive procedures in which the amount of amine present determines the amount of dye which is extracted into an organic solvent have been used for octylamines (111, 131). A somewhat similar method is based on the spectral changes which occur when amines are added to an ethyl acetate solution of bromophenol blue (63). I n modifications of the Van Slyke method for primary aliphatic amines,
the nitrogen liberated by reaction of the amine with nitrous acid is measured by gas chromatography (46, 82). Trace amounts of primary amine derivatives of polynuclear aromatic hydrocarbons have been determined by treatment with pentafluoropropionic anhydride followed by gas chromatography of the resulting pentafluoropropionamides (77). Primary aromatic amines having limited water solubility have been determined by titration with a standard solution of nitrosyl hydrogen sulfate, NOHSOa. The amines are dissolved in a solution containing 1 part WOJOsulfuric acid and 2 parts acetic acid and titrated with a 1M solution of NOHSO, in concentrated sulfuric acid, using a voltammetric end point. The standard solution of nitrosyl hydrogen sulfate is prepared by suitable dilution of the commercial reagent and is standardized against sulfanilic acid ( 9 9 ) . A good coverage of methods for amines and related compounds has been published recently (66). Coulometric methods and catalytic thermometric titmtions for the determination of micro amounts of weak bases have been compared (116). Amino Acids. Strongly fluorescent compounds are formed by the reaction of amino acids with phthalaldehyde in alkaline media in the presence of a reducing agent such as 2-mercaptoethanol. The technique is useful for automatic determination of amino acids ( 9 9 ) . The sensitivity, in the nanomole range, is higher than that with ninhydrin procedures. A new synthetic amino acid, S-8(4-pyridylethyl)-ccysteine1 has been recommended as an internal standard for automated amino acid analyses (18). The compound is stable to conditions of acidic protein hydrolysis and its ninhydrin color is linear with concentration. 2-Nitro-1 ,&indandione and its 4 , s dimethoxy, 4-chloro, 5iodo, and 4-nitro derivatives have been reported to give a violet color with proline, hydroxyproline, and ornithine and a red-brown color with tryptophan. The reactions have been used for detection on paper chromatograms and for quantitative colorimetric determinations after the color has been extracted from the paper ($6). The use of sulfonated polystyrene resins for the chromatographic determination of amino acids has been reviewed (78). Derivatives of amino acids suitable for gas Chromatographic analysis are produced in a single process in which the amino acid is treated with sodium hydride and isopropyl bromide in dimethylsulfoxide. I n most cases the N,Odiisopropyl derivatives are formed. Cysteine gives the N ,O,S-triisopropyl derivative (91).
The determination of tryptophan in the presence of tryosine, as in peptides and proteins, by its absorption in the ultraviolet is complicated by the somewhat similar absorptions of the two substances. A new procedure, utilizing magnetic circular dichroism, has been developed which takes advantage of the fact that tryptophan has a positive magnetic circular dichroism Cotton effect, whereas the effect for tyrosine is negative (21). N-Methylamino acids have been determined with a commercial amino acid analyzer by decreasing the eluting bufTer flow rate from 68 to 34 ml/hr. This modification increases the ninhydrin color constants observed for the N-methylamino acids by 10-20 times. The optical purity of the N-methylamino acids can be determined to =tl% by using the analyzer for separation of the diastereoisomeric dipeptides prepared by coupling of the amino acids with N-carboxyl->alanine anhydride (16).
The determination of amino acid hydrazides and peptide hydrazides has been accomplished by a simple titration with perchloric acid in acetic acid solution, using methyl violet as indicator. For titrations in an aqueous solution, an oxidizing titrant (permanganate or hypobromite) can be used with a methyl red indicator (B9). Aromatic Hydrocarbons. A colorimetric method for aromatic hydrocarbons utilizes the color obtained by treatment of the sample with formaldehyde and sulfuric acid ( 6 ) . For the determination of the aromatic content of complex hydrocarbon mixtures, NMR spectrometry provides a convenient method. The technique
0
Quasilinear fluorescence spectra have been used for determining perylene, 1,l%benzoperylene and 3,4benzopyrene (88). The determination of polynuclear aromatic hydrocarbons has been reviewed by Marletta and Gabrielli (74) and by Gupta and Kumar (37). Azomethines. The analytical chemistry of these compounds has been reviewed in detail recently ( 1 9 ) . Carbohydrates. I n a n indirect iodometric method for glucose, galactose, and xylose, N-bromosuccinimide was used as a n in situ source of hypobromite for oxidation ( 7 9 ) . Relative errors of up to 6% were observed. The absolute standard deviations were 0.010.2 mg for determining 1-10 mg of sugar. I n a micromethod for the determination of Zdeoxyhexoses, the sugars are degraded in 4N hydrochloric acid a t 80 "C to give a product whose absorbance a t 217 nm is linear with concentration (23). Reduction of aldoses to the corresponding alditols followed by treatment with trifluoroacetic anhydride in ethyl acetate gives triffuoroacetates which have been separated and quantitatively determined by gas chromatography (42). On columns packed with XF-1105 on Gas-Chrom P the relative retention times of the derivatives were ribose, 0.70; arabinose, 0.85; xylose, 1.00; mannose, 1.44; glucose, 1.92; galactose, 2.12; fucose, 0.57; rhamnose, 0.42; Zdeoxyribose, 0.55; Zdeoxyglucose, 1.23; Zdeoxygalactose, 1.57. Periodate oxidation of carbohydrates gives formaldehyde. This formaldehyde can be condensed with ammonia and 2,4-pentanedione to give 3,bdiacetyl-ll4-dihydro-2,6-dimethy1pyridine.
0
consists essentially of integration of the aromatic protons and the side chain protons, using a 10% solution of tetramethylsilane in carbon tetrachloride as a reference (27). In another method utilizing NMR spectrometry, the chemical shift for toluene was found to vary linearly with concentration up to 84.2 mole % in light hydrocarbon fractions. The signal for the methyl group of toluene shifts 0.22 ppm as the concentration is changed over the above range. The change for the aromatic protons is 0.085 ppm (121). An infrared method for determination of aromatic content of lubricating oil stocks is based on the absorbance a t approximately 1613 cm-'. Standards ' aromatics gave containing 10-50 wt. % a linear calibration curve (SO).
This last compound can be measured by fluorimetry. The above sequence of reactions has been made the basis of a sensitive, automated spectrofluorimetric method for the determination of carbohydrates (113). Caution must be exercised if amino acids are present in the sample. Most amino acids will give no more than small amounts of formaldehyde, but serine gives one equivalent. Carbon-Methyl Groups. I n some recent investigations on substituted toluidines, it was found that the method of Awasthy, Belcher, and MacDonald ( 6 ) , using vanadium pentoxide with chromic acid and sulfuric acid, gave results comparable to those obtained by the Wiesenberger method (126) and in a shorter time ( 7 5 ) . Essentially quantitative yields of acetic
ANALYTICAL CHEMISTRY, VOL. 44, NO. 5, APRIL 1972
209R
acid were obtained with N-substituted m-toluidines. I n methylpyridines, an amino or hydroxy group a t the 2 position caused an increase in the yield of acetic acid. Carboxy, cyano, and hydroxymethyl groups did not cause an increase in yield ( 7 6 ) . As can be seen from the results obtained above, this well known method must be used with caution, and care must be exercised in interpreting the results. Ideally, one should have for comparison a model compound closely related structurally t o the unknown. Pyrolysis of alkylbenzenes a t 600 "C gives a large amount of styrene and CY-methylstyrene,as determined by gas chromatography. In a rather special case of C-methyl determination, the ratio of the two peaks has been used as an indication of the amount of chain branching in the alkylbenzenes (118). I n many cases the simplest determination of C-methyl groups is by use of time-averaged NMR, using trinitrobenzene as a standard (61). Epoxides. I n two methods used for epoxy resins, the addition of hydrogen bromide to the oxirane ring is the basis for the determinations. I n one method (IO), the epoxide was titrated directly with hydrogen bromide, using a methyl orange indicator. I n the other method ( 1 4 , excess hydrogen bromide was treated with excess silver nitrate and the excess silver was titrated with ammonium thiocyanate. Terminal epoxides have been determined by quantitative reaction with methanol in the presence of boron trifluoride to give primary and secondary hydroxy methyl ethers which can then be determined by gas chromatography (33). Esters. Ester groups in acrylic polymers have been determined by cleavage of the esters with hydrogen iodide (Zeisel method) to give alkyl iodides which were then determined by gas chromatography ( 2 ) . Esters in fats and oils have been determined by lipase-catalyzed hydrolysis, followed by conversion of the acids to methyl esters (sulfuric acid catalyst) and gas chromatography of the methyl esters ( 3 ) . A differential scanning calorimeter has been applied to the determination of 1-monopalmitin in mixtures with 2monopalmitin. An exothermic peak due to crystallization of the 1-isomer is proportional to the amount of that isomer present (110). Both 0-acyl and N-acyl determinations have been reviewed in detail (43). Ethers. A convenient apparatus has been described for use with the Mitsui gravimetric method (82) for determining methoxyl and also methylimide groups (112). A modification of the iodometric method for the determination of iodine 210R
and alkoxyl groups (70, I N ) has increased the sensitivity so that samples of 100-300 pg can be used with I. A.. Microchem.-J..’ 16. 273-6 (1971). (24) Dubinski;, R. A.; Klimova, V. A , , Izv. Akad. Nauk S.S.S.R., Ser. Khim., 1970, 1476-81. (26) Eglite, G., Oskaja, V., Latv. PSR Zinat. Akad. Vestis. Kam. Ser., 1971, 179-81. (26) Emelin, E. A , , Tr. Konf. Anal. Khim. S e b o d n . Rastvorov I k h F i t . Kim. Svozstvam, 1st 1968, 1, 127-30. (27) Esparza, C., Maria, de J., Aceves, P. P., Manjarrez, A,, Ret. Inst. X e s . Petrol., 3, 52-7 (1971). (28) Fontanille, PIT., Tersac, G., Bull. SOC.Chinz. Fr., 1971 , 206C8. (29) Fridkin, M., Goren, €1. J., Experientza, 26, 561-2 (1970).
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(30) Fujita, M., Tauda, A., YzckcrgcJu, 20, 212-17 (1971). (31) Gabor, T. Nagy, J. Period. Polytech., Chem. hng., 14, 1h-30 (1970). (32) Gilman, H. Cartledge, F. K., J. Organometal. Chem., 2, 447 (1964). (33). Glowacki, C. R., Menardi, P. J., Link, W. E., J . Amer. Oil Chem. SOC., 47,225-8 (1970). (34) Goral, X . , Jaworski, M., Chem. Anal. (Warsaw), 15, 629-34 (1970). (35) Gorog, S., Szepesi, G., Actcr Pharm. Hung. 41, 25-9 (1971). (36) Grassetti, D. R., U.S. Patent 3,597,160, Aug. 3, 1971, Appl. Apr. 2, 1969. (37) Gupta, P. L., Kumar, P., Petrol. Hydrocarbons 6, 14F5 (1971). (38) Hall R. 'k., Mair, R. D., Treatise Anal. dhem.. 14. 259-93 (1971). (39) Hanna, J: G.; Anal. Chem. Nitrogen Its Com ounds, 1970, 553-56. (40) Hinc ers, H. J., Blutalkohol, 6, 63-6 (1969). (41) Hirozawa, T., Treatise Anal. Chem., 14, 23-160 (1971). (42) Imanari, T., Arakawa, Y., Tamura, Z.. Chem. Pharm. Bull. 17, 1967-9 (1969). (43) Inglis, A. S., Treatise Anal. Chem., 14, 161-98 (1971). (44) Ibid., p 199-257. (45) Ito, Aikawa, S., Hara, T., Nivnon Kaaaku Zasshi. 91. 251-4 (lQi0). (46) Jones, D., Gerber, L. P., Drell, W., Clin. Chem., 16,402-7 (1970). (47) Jung, G:, Breitmaier, E., Voelter, W., Fresenaus' Z . Anal. Chem., 252, 304-6 (1970). . . (48) Jung, G.,, Voelter, W., Breitmaier, E., Makrochzm. Acta, 1970, 850-4. (49) Jung, G. Voelter, W., Breitmaier, E., Bayer, h., Anal. Chim. Acta, 52, 382-5 (1970). (50) Jurecek, M., Kozak, P., Pure Appl. Chem., 25, 741-62 (1971). (51) Kasler, F., Mikrochim, Acta, 1970, 702-7... (52) Kawahara, F. K., Enuiron. Sci. Technol., 5, 235-9 (1971). (53) Kigasawa, K., Shimizu, H., Fujino, M., Yakugaku Zasshi, 90, 308-16 (1970). (54) Klimova, V. A., Dubinskii, R. A., Itv. Akad. Nauk S.S.S.R., Ser. Khim., 1971, 877-9. (55) Klimova, V. A,, Zabrodina, K. S., ibid., pp 658-9. (56) Konishi, K., Mori, Y., Taniguchi, N., Analyst (London), 94, 1006-9 (1969). (57) Korenman, I. M., Kurina, N. V., Peshcherkova, T. Y., Tr. Kham. Khim. Tekhnol.. 1969, 136-9. (58) Korenman, I. M., Sheyanova, F. R., Kalugin, A. A., Popova, N. A., ibid., 1968, 58-63. (59) Kozak, P., Sb. Ved. Pr., Vys. Sk. Chemickotechnol., Pardubice, 1968, 231378. (60) Kozak, P., Kodejska, C., Jurecek, M., ibid., 1969, 55-65. (61) Kramer, D. N., Hackley, E. B., Anal. Lett., 4, 223-30 (1971). (62) Kramer, D. N., Tolentino, L. U., ANAL.CHEM.,43, 834-7 (1971). (63) Kreshkov, A. P., Drozdov, V. ,A., Romanova, A. D., Zh. Anal. Kham., 24, 1407-11. I
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44,NO. 5, APRIL 1972
(98) Robinson, J. W. Truitt, D., Spectrosc. Lett. 2, 203-ld (1969). (99) Roth, ANAL.CHEM.,43, 880-2 11071 ,--.- ). (100) Skders, E. B., Schubert, J., ibid.,
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