Kinetic aspects of analytical chemistry - ACS Publications

(88) Oles, P. J., Siggia, S„ Anal.Chem., 46, 911-14 (1974). (89) Panasenko, A. A., Vlasova, N. M., Sultanova, V. S., Zavod. Lab., 42, 411. (1976); C...
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(81) Morgenlie, S.,Carbohydr. Res., 41, 285-9 (1975). (82) Mosescu, N., Kalmutchi, G., Pop, V. I., Rev. Chim. (Bucharest), 27, 897-9 (1976); Chem. Abstr., 87, 72815p (1977). (83) Muraca, R . F., in "Treatise Anal. Chem.", Vol. 15, 251-346, Kolthoff, I. M., Elving, P. J., Ed., Wiley, New York, N.Y. (1976). (84) Muraca, R. F., in "Treatise Anal. Chem.", Voi. 15, 385-501, Kolthoff, I. M., Elving, P. J., Ed., Wiley, New York, N.Y. (1976). (85) Nakanishi, A., EiselKagaku, 21, 271-4 (1975); Chem. Abstr., 84, 129964f ( 1976). (86) Obtemperanskaya, S. I., AWuCAziz, A,, Kuvshinnikova, S. V., Vestn. Mosk. Univ., Khim., 16, 374-5 (1975); Chem. Abstr., 84, 12131r (1976). (87) Obtemperanskaya, S. I., Abdul-Aziz, A,, Vestn. Mosk. Univ., Khim., 16, 497-8 (1975); Chem. Abstr., 84, 8 3 7 8 6 ~(1976). (88) Oles, P. J., Siggia, S., Anal. Chem., 46, 911-14 (1974). (89) Panasenko, A. A., Vlasova, N. M., Sultanova, V. S., Zavod. Lab., 42, 411 (1976); Chem. Abstr., 85, 47901q (1976). (90) Pei, P. T. S., Kossa, W. C., Ramachandran, S., Henly, R. S.,Lipids, 11, 814-16 (1976). (91) Pesez, M., Bartos, J., Talanta, 21, 1306-7 (1974). (92) Picer, M., Ahel, M., Picer, N., Nafta(Zagreb), 28, 99-102 (1977): Chem. Abstr., 87, 43993q (1977). (93) Pietrogrande, A., Dalla Fini, G., Malesani, G., Mikrochim. Acta., 1977, 2, 51-4; Chem. Abstr., 87, 161236t (1977). (94) Polumbrik, 0. M., Zhurba, A. S.. Yarmolyak, B. M., Zh. Anal. Khim., 31, 2436-9 (1976); Chem. Abstr.. 86. 1 8 2 6 6 1 (1977). ~ (95) Polyanskii, N. G., Fedorov, V. A., Sapozhnikov, V. K., Zh. Anal. Khim.. 1975, 1809-11; Chem. Abstr., 84, 69093) (1976). (96) Pribyl, M., Semenkova, L., Fresenius' 2. Anal. Cbem., 278, 347-51 (1976); Chem. Abstr., 85, 28326q (1976). (97) Qureshi, M., Khan, I. A.. Anal. Chim. Acta, 88, 309-11 (1976). (98) Remark, J. F., Reynolds, C. A,, Talanta, 23, 687-9 (1976). (99) Revel'skaya L. G., Khripunov, A. K., Klenkova, N. I.. Khim. Drev., 1977, 51-4; Chem. Abstr., 87, 24995a (1977). (100) Rinde, E., Troll, W., Anal. Chem., 48, 542-4 (1976). (101) Riva, A., Blscognani, M., Vaccari, A,, Ind. Conserve, 50, 106-8 (1975); Chem. Abstr., 84, 12113m (1976). (102) Ruch, J. E., Anal. Chem., 47, 2057-8 (1975). (103) Sawicki, E., Sawicki, C. R., "The Analysis of Organic Materials; Aidehydes-Photometric Analysis", Vol. 2 and 3, Academic Press, New York, N.Y. (1975).

(104) Schilt, A. A., Martinie, G. D., Anal. Chem.. 48, 447-9 (1976). (105) Selig, W., Microchem. J., 21, 92-7 (1976). (106) Sharma, J. P., Shukla, V. K. S.,Dubey, A. K., Mikrochim. Acta, 1977, I , 357-61. (107) Shukla, V. K. S.. Dubey, A. K., Sharma, J. P., Anal. Lett., 9, 975-81 ( 1976). (108) Siggia, S.,Hanna, J. G., Cutmo, R., Anal. Chem., 33, 900-901 (1961). (109) Smith, W. T., Jr., Patterson, J. M., Anal. Chem., 48, 84R (1976). (110) Smolova, N. T., Burmistrova, T. I . , Kreshkov, A. P., Zh. Anal. Khim., 30, 1805-9 (1975); Chem. Abstr., 84, 69092h (1976). (111) Stastny, M., Vulterin, J., Waidman, M., Chem. Prum., 26, 648-51 (1976); Chem. Abstr., 87, 33281s (1977). (112) Stegmann, H. B., Uber. W., Scheffler, K., Fresenius' Z. Anal. Chem.. 286, 59-64 (1977). (113) Stock, J. T., Doane, L. M., Anal. Chim. Acta, 86, 317-22 (1976). (114) Szumilo, T., Chem. Anal. (Warsaw). 21, 237-43 (1976); Chem. Abstr., 85, 56283s (1976). (1 15) Tamura, Z., Tanimura, T., Kasai, Y., Japan Kokai, 75 120683, 22 Sept. 1975; Chem. Abstr., 84, 1299729 (1976). (1 16) Tamura, Z.,Tanimura, T., Kasai, Y., U.S. Patent 3980433 (Ci. 23-230M; G01N33116), 14 Sept. 1976; Appi. 73/115712. 12 Oct. 1973, 5 pp; Chem. Abstr., 86, 83299d (1977). (117) Tan, L. K.. Patsiga. R . A., Anal. Lett., 10, 437-49 (1977). (118) Toba, T., Adachi, S., J . Chromatogr., 135, 411-17 (1977). (119) Van Tilborg, W. J. M., J . Chromatogr., 115, 616-20 (1975). (120) Verma, B. C.. Kumar, S., Talanta, 22, 921-2 (1975). (121) Viebock, F., Brecher, C., Ber.. 636, 3207-10 (1930); Chem. Abstr., 25, 896 (1931). (122) Vulterin, J., Sb. Vys. Sk. Chem.-Techno/. Praze, Anal. Chem., 1976, H11. 101-13; Chem. Abstr., 86, 1 5 0 1 2 9 ~(1977). (123) Vulterin J., Straka, P., Chem. Prum., 25, 307-9 (1975); Chem. Abstr., 83, 188023a (1975). (124) Vulterin, J., Straka, P., Chem. Prum., 26, 242-4 (1976); Chem. Abstr., 85, 116331t (1976). (125) Vulterin, J., Straka, P., Sb. Vys. Sk.Chem.-Technoi. Praze, Anal. Chem., 1976, H11, 257-63; Chem. Abstr., 86, 1 3 3 1 5 1 (1977). ~ (126) Wasik, S. P., Brown, R. L., Anal. Chem., 48, 2218-19 (1976). (127) Yoshikawa, T., Inaike, T., Kido, K., Japan Kokai, 7661 883, 20 May 1976; Chem. Abstr., 85. 78904x (1976). (128) Zeisel, S., Fanto, R., Z. Landwirtsch Versuchen., 5, 729 (1902).

Kinetic Aspects of Analytical Chemistry Ronald A. Greinke Union Carbide Corporation, Carbon Products Division, 72900 Snow Road, Parma, Ohio 44 130

Harry B. Mark, Jr.' Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 4522 7

This review surveys the literature from December 1975 through November 1977. T h e format is similar to the 1976 Annual Review. This review classifies the recent literature according to catalyzed reaction rate methods, uncatalyzed reaction rate methods, differential reaction rate methods for the determination of mixtures, and instrumental, computer, and miscellaneous kinetic methods.

CATALYZED REACTION RATE METHODS As in past years, the most frequently used approach for kinetic determinations is catalyzed reactions. The main advantages that catalyzed reaction rate methods offer to analysts are very sensitive and, in some cases, very specific determinations. A symposium on "Kinetic and Catalytic Methods" was chaired by G. G. Guibault a t the 172nd National ACS meeting in San Francisco, Calif., 1976. A comprehensive review of catalyzed reaction methods was presented by Mueller and Werner ( I ) . Weisz ( 2 ) reviewed the use of catalyzed reactions in analytical chemistry. Weisz and Meiners (3)followed simultaneously the course of catalyzed reactions with two independent indication

systems. The use of two rate indicators improved the precision and accuracy of the determination of the catalysts iron, cyanide, and molybdenum. Weisz ( 4 ) and co-workers reported the application of catalyzed reactions to semiquantitative determination of vanadium, copper, cobalt, and silver by a ring oven technique. Delumyea and Hartkopf ( 5 ) have applied the metal catalyzed chemiluminescence reaction of luminol with hydrogen peroxide, as a means of monitoring the metal ions in effluents from anion-exchange columns. The authors show that the application of chemiluminescence detectors is not limited to a single solvent and that strongly acidic eluents, commonly used in ion exchange separations, can be successfully neutralized in the flow stream. A unique analytical application of heterogeneous catalysis was described by Dutt and Mottola (6) for the determination of palladium(II), which was found to significantly increase the rate of reduction of organic dyes by hypophosphite after a brief induction period. In the final step of the catalytic process, hypophosphite reduces Pd(I1) to Pd(0). In contact with finely divided metallic palladium, hypophosphite decomposes producing hydrogen which reduces the dye. The length of

ANALYTICAL CHEMISTRY, VOL. 50, NO. 5, APRIL 1978 Ronald A. Greinke, Staff Scientist for the Carbon Products Division, Parma Technical Center, Union Carbide Corporation, Parma, Ohio, received his B S degree from the University of Illinois in 1963, and his M S and Ph D in analytical chemistry from &e Unrversity of Michigan in 1965 and 1967, respectively Dr Greinke joined Union Carbide Corporation in 1967 as an analytical chemist in peracetic acid and peracetic acid derivatives production 4) for the Chemicals and Plastics Drvision at South Charleston, W Va In 197 1, he became head - 3 of analytical research and development at the Parma Technical Center HS research interests includes kinetic methods of analysis, gas chromatography, thermal analysis, polynuclear aromatic hydrocarbon analysis, and environmental analysis. He has published research papers in these areas, is a co-author of the book "Kinetics in Analytical Chemistry", and the chapter "Carbon" which was published in the "Treatise of Analytical Chemistry". Dr. Greinke is a member of Sigma Xi and was past chairman of the Cleveland Analytical Topics Group, ACS.

Harry B. Mark, Jr., Professor of Chemistry and Head of the Department of Chemistry, University of Cincinnati, received his B A degree from the Unrversrty of Virginia in 1956 and his Ph D degree from Duke University in 1960 He was a postdoctoral research assoclate at the Universty of North Carolina (with C N Reilley) from 1960 to 1962 and at the Californla Instrtute of Technology (wth F C Anson) from 1962 to 1963 He was a member of the staff of the Department of Chemistry at the Universty of Michigan from 1963 to 1970, Vishng Professor of Chemistry at the Universitd Libre de Bruxelles, 1970, and joined the staff at the University of Cincinnati in 1970 His research interests are in electrochemistry, surface chemistry, kinetic methods of analysis, environmental analytical problems, and instrumentation In addtion to research papers, he is the cc-author of the books Kinetics in Analytical Chemistry , 'Activated Carbon. Surface Chemistry and Adsorption from Solution", and SimplifiedCircurt Analysis, DigrtaCAnalog Logic" He is also a co-editor of the monograph series Computers in Chemistry and Instrumentation', and 'Water Quality Handbook' , and a member of the Edltorial Board of Analytical Chemistry, Analytical Letters Chemical Instrumentation and Manta

the induction period is inversely proportional to the palladium concentration. Chromium catalytic methods were reported by several workers. Efstathiou and Hadjiioannou (7) developed a method based on the accelerating effect of chromium(II1) on the periodate-arsenite reaction. T h e reaction was followed by a perchlorate-selective electrode which responds t o periodate. Rigin and Bakhmurov (8) proposed a kinetic method for chromium(II1) which catalyzes the chemiluminescence reaction between luminol and hydrogen peroxide. Chromium(II1) or (IV) also catalyzes the reaction between hydrogen peroxide and salicylal-H-acid. Tashkhodzhaev et al. (9) used this reaction to determine trace amounts of chromium in silicate rocks and aluminum sulfate. Wolf and Schwing (61)described the determination of chromate, molybdate, and tungstate based on their catalysis of the oxidation of iodide by bromate. A number of catalytic methods for cobalt were reported. T h e method of Trofimov et al. (10) is based on the catalytic action of cobalt(I1) on the oxidation of derivatives of diantipyrinylmethane by hydrogen peroxide. The lower limit of determination is 0.16 pg/mL. Kreingol'd e t al. (12) also determined cobalt in alkali metal salts by measuring its effect on the rate of reaction between catechol and hydrogen peroxide. Cobalt was assayed by Pantaler et al. (13)who based the method on the decomposition of hydrogen peroxide by Co(II)-2-aminopyridine. Three catalytic methods for copper were described. The rate of reaction of hydrogen peroxide with sulfanilic is proportional to the concentration of cobalt, by using this reaction, Aleksiev et al. (14, 15) determined copper in blood serum. Nanogram amounts of copper in zinc salts were determined based on the inhibition of the iodine-azide reaction by the copper-thioammeline complex (16). Weisz et al. ( 1 7 ) reported that the onset of the copper(I1) catalyzed decomposition of

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hydrogen peroxide is delayed in the presence of cyanide. Both copper and cyanide were determined a t the kg level. Yatsimirskii and co-workers (18)described a kinetic method for gold. The reduction of Ce(1V) to Ce(II1) by As(II1) is catalyzed by iodide and inhibited by gold(II1). Gold was also determined by Kurzawa e t al. (19) who employed the inhibition of the iodine-azide reaction by the 2-mercaptopurine-gold complex. The oxidation of luminol, catalyzed by iridium(IV1, was the basis of a kinetic method presented by Lukovskaya and Kushchevskaya (20). Many catalytic methods were reported for iron which involved the use of the oxidant hydrogen peroxide. The methods are based on the oxidation of luminol(21), p-phenetidine (22, 26), 2,4-diaminophenol (23), diphenylcarbazone (24), and Redoxin I1 (25) (acu-diantipyrinyl-3,4-dimethoxytoluene) catalyzed by iron. The methods were applied to the determination of iron in high purity lithium, potassium, rubidium, and cesium chlorides (21), magnesium sulfate (22), optical fibers (23),and potable water (24). Ohashi et al. (27) also determined iron based on the iron(II1) catalyzed reduction of tris(oxalato)cobaltate(III) by ascorbic acid. Catalytic methods for the determination of manganese are numerous. Nikolelis and Hadjiioannou (28)used the catalytic effect of manganese on the periodate-phosphinate reaction to determine manganese in natural waters. Their method was also used for the determination of nitrilotriacetic acid and 1,2-diarninocyclohexane-N,N,N',"-tetraacetic acid on the basis of the activating and inhibiting effect, respectively, on this reaction. Efstathiou and Hadjiioannou (27) used a periodate-sensitive perchlorate ion-selective electrode in the kinetic determination of manganese(I1) by its catalytic effect on the periodate-acetylacetone reaction. Efstathiou and Hadjiioannou (30) applied this same electrode to study the periodate-a-amino alcohol reactions. They found that manganese(I1) strongly catalyzes the periodate-triethanolamine reaction in the presence of the activator, trinitrilotriacetic acid. The method of Pantaler et al. (31,32)involved the catalytic action of the manganese(I1)-1,lO-phenanthroline complex on the decomposition of hydrogen peroxide. T h e oxidation reaction of thymol blue with potassium periodate was found t o be catalyzed by manganese (33). A kinetic method for mercury in serum, urine, pharmaceutical preparations, air, and water was proposed by Schurig and Mueller (34). Mercury catalyzes the reaction between Fe(CN)?- and water. T o increase the selectivity of the catalytic determination of molybdenum in seawater, Otto and Muller (35) first extracted molybdenum by complexation with oxinate. T h e catalyst was then determined directly in the organic extract based on its effect on the rate of oxidation of 1-naphthylamine by bromate. Kurzawa and Kubaszewski (36) assayed for microgram amounts of nickel in margarine based on its inhibition of the iodine-azide reaction by the nickel-diethyldithiocarbamate complex. Alekseeva et al. (37)determined niobium by measuring its effect on the raLe of oxidation of thiosulfate with hydrogen peroxide. Alekseeva et al. (38)studied conditions for separating micro amounts of osmium prior t o kinetic determination. These same authors also studied the conditions for preparing standard solutions prior to kinetic determination (39). The oxidation of 1-naphthylamine by nitrate is catalyzed by osmium(VII1) and ruthenium(VII1). Mueller and Otto (40)used this reaction to measure nanogram quantities of catalyst. Yatsimirskii and co-workers (41) reported the optimum conditions for determining osmium(VIII), which catalyzes the oxidation of p-phenylenediamine with hydrogen peroxide. Khain et al. (42) described the kinetic determination of osmium based on the catalyzed reduction of potassium ferricyanide by sodium tetrahydroborate. A kinetic method for palladium was proposed by Yatsimirskii e t al. (43). Palladium catalyzes the oxidation of chloride with manganese(II1). A chemiluminescence kinetic determination of as little as 0.04 pg of platinum was described by Rigin e t al. (44). Platinum(1V) catalyzes the oxidation of luminol by H2O2. Morozova et al. (45)separated rhodium from the platinum group metals by thin-layer chromatography. After extracting

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the rhodium(II1) from the plate, rhodium was determined by a kinetic method based on its catalytic action on the oxidation of Mn(I1) with bromate. Tikhonova et al. (46) assayed rhodium based on its catalytic effect on the oxidation of copper(I1) by periodate. T h e method of Rysev e t al. (47) for ruthenium involves catalysis by ruthenium(1V) of the oxidation of methyl red by periodate. A new sensitive catalytic method for determining selenium was proposed by Kawashima et al. (48). Selenium catalyzes the oxidation of p-hydrazinobenzenesulfonic acid to p-diazobenzenediazonium ion, which then is converted to a yellow azo dye by coupling with rn-phenylenediamine. Two kinetic methods were proposed for silver. Wilson and Ingle (49)based their method on the enhancement by silver(1) of the reaction between oxine-5-sulfonic acid and persulfate. A dithizone silver extraction procedure, developed to eliminate interferences, was applied to NBS zinc spelter analysis. DeOliveira and Meditsch (50) employed the silver catalyzed reduction of Ce(1V) by chloride. Kuroda et al. (51) assayed for traces of tellurium(1V) by catalytic reduction of tartrate by chloride. Regin and Alekseeva (52) quantified tin by its catalytic effect on the reduction of isopolymolybdate by ascorbic acid. A kinetic method for tungsten, described by Pavlova et al. (53),was based on the reduction of triarylmethane dyes with titanium(II1). Several procedures for vanadium were reported. Fukasawa and Yamane (54)determined as little as 0.03 ppb of vanadium in natural waters. Vanadium, separated and concentrated by a combined cation- and anion-exchange procedure, catalyzes the oxidation of gallic acid by bromate (56). Pilipenko (55) reported that vanadium(1V) catalyzes the chemiluminescence reaction of luminol and hydrogen peroxide. Numerous catalyzed reactions were reported to quantify inorganic anions. Ottaway and co-workers (57)found that bromide inhibited the bromate-methyl orange reaction. Carbonates were assayed by Pantaler and Pulyaeva (58),who employed the complexation reaction between chromium(II1) and xylenol orange, catalyzed by carbonates. Mentasti and Pelizzetti (59) determined chloride and bromide by their inhibition of the oxidation reaction of 4,4’-dihydroxybiphenyl with Tl(II1). Cyanide catalyzes the reaction of 4-nitrobenzaldehyde and 1,2-dinitrobenzene. Okutani et al. (60) used this reaction to determine as little as 0.01 ppm cyanide in waste water. A catalytic-kinetic method for the determination of nanogram amounts of fluoride, based on its inhibiting action on the catalyst in the zirconium-catalyzed reaction between perborate and iodide, was described by Klockow and Auffarth (62). This reaction was modified to a Landolt-system by adding a small amount of ascorbic acid. Similarly, Gaal et al. (63) determined fluoride using the bromate-bromide reaction. Many methods for iodide were described. Jasinskiene and Umbraziunaite quantified iodide based on its acceleration of three different reactions, the oxidation of catechol violet by iodate (64),the oxidation of benzidine by hydrogen peroxide (65),and the oxidation of catechol violet by chloramine B (66). Other methods involved the oxidation reaction of SCN- by NOz- and NO< (67),and the photochemical reaction between thionine and EDTA (68). Senn et al. (69) assayed nitrate ions a t the ppb level in environmental samples with a continuous-flow immobilized-enzyme reaction. A catalytic method for thiocyanate was proposed by Utsumi et al. (70), based on its effect on the reaction of iodine and azide. A variety of organic compounds were quantified via catalyzed reactions. Yatsimirskii and co-workers (71) measured ascorbic acid by means of its activation of the oxidation of iodide by C103- in the presence of vanadium(\.’). A procedure for thioketones, described by Richmond e t al. (72),involves the catalytic acceleration of the iodine-azide reaction. Microgram amounts of rubeanic acid and its derivatives were determined by their effect on the iodineeazide reaction (73). Two similar procedures for 8-hydroxyquinoline were presented. In the first, Janjic et al. (74) employed the reaction of Alizarin S and hydrogen peroxide. In the second, 8hydroxyquinoline inhibits the oxidation of Alizarin S by hydrogen peroxide in the presence of cobalt(I1) (75). A kinetic method for vitamin BIZ was described by Sheehan and Hercules (76). Vitamin BIZcatalyzes the oxidation of luminol by H202.

Some organic compounds bond hydrogen ions, and some ligands chelate metal ions in a manner to lower the reduction potential of the hydrogen ion or metal ion a t an electrode surface, which results in a catalytic polarographic prewave. Many researchers published papers which describe the use of the resulting catalytic current for determining such ligands, metal ions, and organic compounds. Toropova et al. (77) determined cyanide based on the catalytic prewave of hydrogen in solutions of nickel-ethylenediamine complexes. Two methods for the ligand, catechol, were proposed. Chikryzova and Kiriyak (78)assayed catechol by measuring the catalytic current in solutions of molybdenum(V1) and chlorate. Tur’yan et al. (79)reported that the magnitude of the prewave current at a DME, in the presence of germanium ions and perchlorate, was proportional to catechol concentration. The polarographic determination of cobalt(II), iron(II), and manganese(II), in the presence of thiourea and ClO;, was reported by Ruvinskii et al. (80). Optimum conditions were established by Astafeva et al. (81)for the ac polarographic determination of copper(II), nickel(II), or cobalt(I1) via the catalytic current of hydrogen ions in the presence of dimethylglyoxime. Nomura and Nakagawa (82) reported the quantification of copper by measurement of the catalytic wave produced in the presence of 2-aminophenol. Ezerskaya et al. (83)observed the mutual catalytic effect of thiosemicarbazide complexes of rhodium and iridium on the reaction of hydrogen ions a t a DME, and used the effect for quantifying microgram amounts of iridium and rhodium. Catalytic waves of hydrogen in the presence of manganese and iron dithiocarbamates were described by Budnikov et al. (84). The waves were rectilinearly related to manganese and iron concentrations. The prewave observed in a solution containing molybdenum(VI), glycollic acid, and chlorate-supporting electrolyte is linearly related to molybdenum concentration (85). Itabashi and Yusa (86)reported the analytical application of the catalytic polarographic current of nickel(I1) in acidified thiocyanate solutions containing cobalt(I1). Cobalt increases the sensitivity of nickel measurements. Alexander et d. (87)gave experimental conditions for the development of the polarographic wave for platinum(I1) after chelation with ethylenediamine. The wave allowed trace determination of platinum(I1) with little interference of other platinum group metals except for rhodium(II1). The technique was applied to the determination of platinum(I1) in ores (88). Titanium(1V) gave a kinetically controlled wave in the presence of n-phenylbenzohydroxamic acid (89) and 2-dibutylphosphinyl-2-hydroxypropionicacid (90). Tungsten(V1) produced catalytic currents in the presence of hydroxylamine and catechol (91),and hydroxylamine and ascorbic acid (92). Demkin (93) showed that derivative polarograms of 0.5 M H2S04containing traces of tungsten(V1) produced a catalytic current for the reduction of hydrogen ions a t a DME. The technique was applied t o measure solubility of H2W04 in water. Toropova and Vekslina (94)observed the catalytic wave of bromate ions a t a rotating graphite-disc electrode in the presence of vanadium(V). The limiting current was proportional to vanadium(V) concentration. Nomura and Nakagawa (95)proposed a polarographic method for 0.2 pg of vanadium based on catalysis of the oxidation of oaminophenol with chlorate. Applications of catalyzed reactions for end-point detection in titrimetric analysis are becoming more prevalent. The main advantage of this approach is more precise end-point detection, especially for the determination of trace amounts of substances, where conventional end-point detection may be difficult. Hadjiioannou et al. (96) reported the determination of pg quantities of EDTA by using the perchlorate selective electrode which responds to periodate. EDTA is titrated with manganese. At the end point, the excess manganese catalyzes the reaction of periodate and diethylaniline. Hadjiioannou and Timotheou (97)titrated either gold(II1) or palladium(I1) with iodide. When excess iodide was added, the titrant catalyzed the reaction of cerium(1V) and arsenic(I1). As little as 1 pg of palladium and 18 pg of gold could be determined. By using the same cerium(1V)-arsenic(II1) end-point reaction, Hadjiioannou and Piperaki (98) titrated mercury(I1) with iodide. Excess iodide catalyzes the Ce(1V)-As(II1) reaction, which results in a detectable change in potential. The acid-catalyzed acetylation reaction of alcohols and phenols with acetic anhydride was used by Greenhow (99)to indicate the end point in the titration of tertiary amines and metal

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carboxylates with perchloric acid. Oxygen deficit in silica was measured by Kreingol'd ( l o o ) ,after treating. the powdered sample with chromium(V1). After reduction by Si(II1) compounds, the excess chromium(V1) is determined kinetically by means of the chromium catalyzed reaction of 1-hydroxy-3-methyl-1-phenylureawith Br03.

UNCATALYZED REACTION RATE METHODS Although the greatest volume of kinetic methods involves catalyzed reactions, the largest growth over the past two years has been in the area of uncatalyzed reactions. Many of the reported methods were novel. Because of lower accuracy, the use of uncatalyzed reactions for determining a single species is not recommended if a suitable equilibrium or nonkinetic method is available. When the reaction, employed for the nonkinetic analysis is slow, reversible, or involves an additional interfering consecutive reaction, an initial reaction rate kinetic method may be advantageous. Dutt, Hanna, and Mottola (101) have applied their novel flow-through cell and flowthrough loop system for the repetitive and continuous photometric determination of iron(I1) in lake water and t a p water. The determination of iron(I1) is based on the fast chemical reaction with ferrozine taking place in the detection zone and the washing out of the signal as a result of the imposed flow. However, the gradual buildup of background signal produced a continuous baseline shift that limited the photometric scale useful for the determination. This problem was eliminated by subsequent conversion of the iron(I1) complex to iron(II1) with oxygen. This favored the reaction of iron(II1) with the ligand, oxalate, which makes a negligible contribution to the absorbance of the circulating solution (102). Similarly, Dutt and Mottola (103) also utilized the flowthrough cell for the repetitive photometric determination of isonicotinic acid hydrazide. The two competitive reactions for this system are the very fast formation of the colored complex between the hydrazide and vanadium(V) followed by a slower destructive oxidation of this complex by excess vanadium(V); 360 samples per hour were assayed. Oteiza et al. (104) described an initial reaction rate method for the determination of hydrocortisone by reaction with blue tetrazollum. An analysis time of 30 s is required. A spectrophotometric kinetic method was proposed by Veres and Csanyi (105) for determination of primary and secondary alcohols by oxidation with chromic acid. The reaction was accelerated by addition of oxalic acid, as a consequence of mutual induction. Efstathiou and Hadjiioannou (106) kinetically identified and determined carbohydrates with a periodatesensitive perchlorate selective electrode. The automated determination of 7 to 54 mg of glucose was achieved in 2C140 s by measuring the rate of the glucose-periodate reaction. The nitric acid esters, glyceryl trinitrate or pentaerythritol tetranitrate, were assayed by Yap et al. (107),based on the rate of degradation in an alkaline methanolic solution. Adrenaline and levodopa were determined by Pelizzetti et al. (108) by measuring the rate of oxidation to benzoquinone with Na21rC1,. Hardy et al. (109) developed a rate method for lo-* to M of penicillin G based on the initial reaction rate with iodine. Extreme sensitivity for penicillin G was obtained since the iodine consumption was monitored by the intense iodine induced chemiluminescence of luminol. Bagdasarov et al. (110) determined methylamines by an initial reaction rate method with p-benzoquinone. A study was made by Yap et al. (111) of the factors affecting the kinetic assay of nitroglycerin in dosage forms. A rapid (20 s) kinetic method for thiocyanate in serum was proposed by Landis et al. (112). The method is based on the reaction of thiocyanate with bromine to form cyanogen bromide which subsequently is reacted with pyridine. The yellow product is monitored by stopped-flow spectrophotometry. Nieman et al. (113) developed an initial reaction rate method for as little as 13 ppb of cyanamide by measuring its complexation with pentacyanoamminoferrate(I1). Hypophosphite in the to IO-' M range was determined by Nikolelis et al. (114) by reaction with iodate. Bartels and Roijers (115) reported a kinetic study on the influence of reaction parameters in the determination of inorganic phosphate by the molybdenum blue reaction. Two papers by Simonescu et al. (116, 117) describe the noncatalyzed kinetic determination of carbon monoxide in the atmosphere (116) and blood (117) by reaction with the Ag complex of Na-4-sulfamoylbenzoate. As little as 5 ppm carbon

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monoxide is spectrophotometrically measured. A kinetic fluorimetric determination of aluminum was reported by Wilson and Ingle (118). The initial rate of reaction of aluminum(II1) with oxine-5-sulfonic acid, measured as a change in fluorescence signal per unit time, was linearly related to the initial aluminum concentration. The detection limit of 0.4 ppb was considerably lower than that obtained by flame atomic absorption. Tamarchenko (119) assayed iron(I1) based on the reaction between iron(I1) and C103-. The rate was measured by monitoring the decrease in extinction of methyl orange which is decolorized by the chloride formed.

DIFFERENTIAL REACTION RATE METHODS The differential reaction rate approach continues to be a useful tool for the simultaneous determination of two- and three-component mixtures with closely related chemical properties. Connors (120) developed a new mathematical approach for the linear graphical analysis of mixtures, A and B. He plotted (Cz"-Cz) exp(hAt)vs. exp(hA- k d t , where 2 is the common product. The slope of the curve is equal to the initial concentration of the slower reacting component, B, and the intercept is equal to the sum of A and B. The method is advantageous over other extrapolation methods when hA/kBis small or when A/B is large because data points a t early reaction times are utilized. The method was applied to the analysis of a mixture of esters subjected to alkaline hydrolysis. Connors (121) also proposed a new graphical interpolation method for the kinetic analysis of three-component mixtures. The concentration-time curve for the production of product, 2,is first determined for the unknown three-component mixture. Then synthetic reference mixtures are subjected to the same reaction under the same conditions and the reaction product, 2,is measured as a function of time. By strategic adjustments of the reference mixtures concentrations, a complete matching of the reference and unknown concentration-time curves can be achieved. The advantage of this approach is that knowledge of the rate constants is not necessary and that synergistic effects of mixtures on rates do not influence the results. Csiz'er and Gorog (122) determined mixtures of CY and 0 ethynodiodiacetates (the latter is a sex hormone present in contraceptive pills) by a single point differential kinetic method. The method is based on the difference between the rates of the acid-catalyzed elimination of acetic acid. Binary mixtures of penicilins were determined by Koprivc et al. (123),who used the logarithmic extrapolation method. The ratio of rate constants and the ratio of initial concentration influenced the accuracy. Mixtures of aliphatic carboxylic acids were assayed by Mentasti et al. (124) based on differences in the oxidation reaction with silver(I1). Because of the very fast halflives (0.1 s), stopped flow techniques were utilized for rate measurements. They employed the method of Roberts and Regan. Mixtures of metal ions were determined by several workers. By measuring the rate of the ligand-exchange reaction between alkaline earth metal cations and the cadmium complex of 1,2-diaminocyclohexanetetraacetic acid, Kopanica and Stara (125) determined mixtures of calcium and magnesium. The rate of cadmium(I1) liberated was followed by square-wave polarography. Molybdenum and tungsten ions were simultaneously determined by monitoring their effect on the rate of reaction between HI and BrO< a t 25 "Cand 40 "C (126). These same two cations were also measured by Collin and Lagrange (127) who used on-line computer techniques for measuring the rates of reaction with hydroxyl. A kinetic method for the simultaneous determination of zinc and cadmium was reported by Haraguchi and Ito (128). The method is based on differences in rates of back-extraction of the metal chelates into aqueous 1,2-diaminocyclohexanetetraacetic acid.

INSTRUMENTAL, COMPUTER, A N D MISCELLANEOUS KINETIC METHODS In the past two years there has been a significant decrease in the amount of publications dealing with instrumentation, detectors, automation, data handling, etc., which have been applied directly to kinetic methods of analysis. However, the opposite is true with respect t o the quantity of papers dealing with applications of mini- and microcomputer systems as applied to laboratory or individual experimental instrument

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automation, ex erimental control, data acquisition and storage, data rejuction, etc., in chemistry in general. In the revious four reviews on “Kinetic Aspects of Analytical hemistry”, we had selected apers on this subject for discussion, which, although they i d not deal with kinetics, could be potentially applied to rate methods and or measurements. This year, we have decided not to include t ese related papers on computer ap lications to instrumentation unless they were directly relatef or actually used in kinetic measurement and/or analysis. The reason for omitting these papers was partly due to the large increase in volume, but also to the fact t h a t there are now appearing numerous comprehensive reviews, monographs, etc., on the subject. Thus, duplication here is not warranted. Weisz and co-workers (129, 130) have continued their development work on different instrumental approaches to the so-called steady-state or “stat” methods of catalytic kinetic analyses. In these “stat” methods, an external means of keeping one of the reactants or reaction products at a constant preset value is employed. They have described a new dual polarized am erometric (“bioamperstat) system which uses an automateztitrator in conjunction with a current-to-voltage transducer to maintain a constant concentration (corresponding to a preset current value) of a titrant in the reaction vessel (129). Its application to the analysis of copper, peroxidase, glucose oxidase, thyroxine, 5-chloro-8-hydroxy-7iodoquinoline, iodine and 1,lO-phenanthroline are discussed. In another paper (130), the three basic approaches for the application of so-called “open systems” in catalytic base kinetic analytical methods are actually discussed: steady-state, “stat”, and continuous flow methods. In addition, the further possibilities and potentialities of (i) the simultaneous addition of one reactant and the catalyst a t constant speed, and (ii) the simultaneous addition of one reactant and the catalyst a t a speed regulated by the system itself, necessary to keep a preset measurement signal (potential or absorbance) are examined. Example analyses of osmium, copper, molybdenum, and manganese are given. Wilson and Ingle (131) have discussed the criteria for the evaluation of “rate meters” for the application to the f i x ed-time rate method. By taking into account the limitations imposed by noise from the reaction monitor, they have developed improved instrumentation employing digital integration of the signal. Dutt and Mottola (102) have continued the development and improvement of their novel bot simple flow-through cell and flow-through loop system for repetitive and continuous injection determinations. All the necessary reagents are contained in a single reservoir and are circulated at constant flow through the measurement cell. An aliquot of the species to be determined is injected into the flow stream rapidly and participates in a rapid reaction which changes the concentration of the measured species. A subsequent but slower reaction regenerates the monitored species chemically. Because the simplicity of the design gives the repetitive capability which allows one to use an ordinary spectrophotometer or electrometric monitor and does not require any expensive automation, it is felt that this approach has great practical application in routine analysis. The application to the analysis of Fe(I1) is used to demonstrate the technique. Porterfield and Olson (132) have devised a very novel differential potentiometric method for measuring the rate of enzyme catalyzed reactions. The electrode cell is a flou stream concentration cell using tubular carbon electrodes separated by a membrane salt bridge. The Nernstian behavior of the cell allows the direct calculation of enzyme activity. They compared the results obtained with this potentiometric method to those obtained using standard AutoAnalyzer techniques. The use of ion-selective electrodes as detectors in flow systems for kinetic analyses has continued to gain attention over the past two years. Mertens et al. (133) have carried out a basic study of the kinetic response of the fluoride ion-selective electrode in fast-flow injection and automated flow systems. They discuss how the kinetic response of the electrode (presumably film diffusion is the rate limiting step) effects the sample rates that can be obtained in the above flow methods. Efstathiou and Hadjiioanna (29,30) have described the application of a perchlorate selective electrode as a periodate sensor in the kinetic determination of manganese and other species. A detailed up-to-date review of the

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continuous flow approach to automated chemical analysis by Snyder et al. (134) contains considerable information on systems applicable to kinetic analysis. The greatest research activity in the development of instrumentation for kinetic and kinetic based analysis has been in the area of stopped-flow methods. Improvements in computer based automation systems and rapid scanning detectors for obtaining time resolved spectra of fast reactions have received the most attention. Ridder and Margerum (135) have developed data handling techniques, including variable rates of data acquisition, linear squares regression analysis, enterin the data, and reparameterization of matrices, for a stoppecf flow spectrometer used in the simultaneous kinetic analysis of multicomponent mixtures. This aper is especially significant and useful as the authors inclufe a t the end nine general recommendations for optimizing or avoiding pitfalls in multiple component kinetic analysis. Mixtures of Hg2+, Cd2+,Zn2+ and Cu2+ in the lo4 to M ran e and epinephrine, norepinephrine and L-Dopa in the 1085 to M range are used as examples to illustrate the applicability and limitations. Ridder and Margerum (136) have also developed a rapid-scanning vidicon based spectrophotometer system which has improved stopped-flow mixing, spectral characteristics, and speed of data handling. The whole system is evaluated in regard to determinant errors (stray light, resolution, and vidicon lag time) and random errors in absorbance measurement The system has been tested experimentally (the analysis of well studied Hg2+ and Zn2+ reactions). A fully automated stopped-flow spectrophotometer with a hierarchial computer control system has been developed by Mieling et al. (137). A microcomputer controls several operations such as preparation of reagents, drawing measured volumes of reagents and sample, and the stopped-flow mixing. A minicomputer is used to control the microcomputer and to carry out data acquisition and processing operations, and makes decisions relative to the acceptability of the data. A particularly significant stopped-flow kinetic study of the Berthelot reaction for the determination of ammonia has recently been published by Patton and Crouch (138). Although not an instrument development paper, the authors show nicely how good instrumentation is used to determine the mechanism and intermediates in a complicated reaction and how this knowledge can be used to improve the analytical utility, sensitivity, and procedures with respect to previous methods. Nieman and Enke (139) have developed a computer controlled rapid scanning spectrophotometer using a silicon vidicon detector which would be applicable to sto ped flow or other rapid kinetic techniques. The applicaklity and limitations are discussed. In the area of instrumentation designed for fast chemical reactions which could be employed for kinetic analysis, Pate1 (140) has designed a combined stopped flow-temperaturejump apparatus which features dual beam detection. A new capacitor discharge system for temperature-jump apparatus which extends the measurement times down to the nanosecond range has been devised by Reich and Sutter (141). Also of possible interest to the analytical chemist is a comprehensive review of fluorescence life time measurements using the time correlated single photon technique by Cline Love and Shaver (142). (The analytical potential of phosphorescence and fluorescence life-time measurements to mixtures had previously been originally demonstrated by Mousa and Winefordner (143).) In the area of development of detection systems for rate measurement and kinetic analysis, Wilson and Ingle (49) and Chen (144) have described the use of fluorescence detection. Of good practical potential for the application of excited state emission of chemical reactions in analysis is the rapid scanning fluorescence system described by Johnson et al. (145). Krug et al. have employed a turbidimeter in a continuous flow injection system (146). Hadjiioannou et al. (147) have designed an automated miniature centrifugal analyzer with spectrophotometric detection. They have employed this unit for the ultra-micro determination of manganese in natural waters. McCreery (148) has published a spectroelectrochemical technique for using optically transparent thin layer electrode (OTTLE) cells for measuring the rates of reaction of electrogenerated reactive intermediates. This approach certainly has possibilities for analysis, although this aspect has not yet been explored.

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Three review papers dealing with com uterized instrumentation and automation should be c i t e t i n this review as they are comprehensive and directed toward analytical measurement. Perrin has recently reviewed applications of minicomputers in chemistry (149) and specifically includes a section on uses in rate measurements. The article by Gochman and Bowie (150) contains useful information on automated systems for radioimmunoassay; parts of such systems could be applicable to automated systems for rate measurement. The critical review of computer networking as applied to laboratory automation problems by Dessy is particularly valuable (151). Also of interest is the pa er on reaction kinetics as studied by differential thermal anafysis by Yang and Steinberg (152). LITERATURE CITED (1) Mueller, H., Werner, G., Z.Chemie, 16, 304 (1976). (2) Weisz, H., Angew. Chem. Int. Ed. Engl., 15, 150 (1976); Anal. Abstr., 31, 202 (1976). (3) Welsz, H., Meiners, W., Anal. Chim. Acta, 90, 71 (1977). 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Electron Microscopy John M. Cowley Department of Physics, Arizona State University, Tempe, Arizona 8528 7

T h e past two years have seen developments in the instrumentation and techniques of electron microscopy which, while not fundamentally new, provide important advances in the power of the instruments as research tools in many areas of science. Since previous reviews in this series have tended to emphasize advances relevant to biological applications, this review will be written more from the viewpoint of users in the materials sciences and will include some reference to achievements previous to this two-year period. The overlap with the interests of biologists is still considerable.

INSTRUMENTATION CTEM Instruments. The new generation of commercial 100-ke\' high resolution transmission electron microscopes offers several important improvements in performance. \lost notable, for many purposes, is the improved vacuum. \Vhereas pre\iously the yacuum in the specimen region was rarely much betrer than 10 Torr, it is now possible to achieve better than IO-.Torr with the aid of additional, clean pumping systems. l h e incentive for this development was, in part, the need for good vacuum in the microscope column which would not degrade the very much better vacuum in the gun chamber needed for the operation of field emission guns. However. the lower gas pressure in the specimen area should reduce greatly the contamination of the specimen which occuri under electron irradiation. For the imaging of thin specimens with atomic-level resolution, this will eliminate much of the unwanted background contrast (noise) of the images. It will allow more convenient use of the microdiffraction methods employing very fine electron beams [see below). It will allow the surface structure of crystals to be imaged with greatly improved clarity and convenience. Improvements in stability of the high voltage supplies and lens currents. together with the development of special high resolution pole-pieces for the lenses (with the spherical aberration constant as low as C, = 0.: mm in m e case) have allowed better resolution, as demonstrated by several groups in Japan. Hashimoto et al. (18) have publiihed pictures ( i t ' thin gold crystals in [lo01 orientation showing clearly the intensity maxima corresponding to the projected ro\vs of gold

atoms 2 A apart and also showing intensity variations on a scale of about 0.5 8, within these maxima. Although these details are not directly interpretable in terms of specimen structure they demonstrate a major advance in instrument performance. Izui e t al. (29) have obtained images showing projections of thin silicon single crystals in the [110] orientation with well-resolved spots corresponding to silicon atom positions 1.36 A apart. It must not be assumed that these images represent a resolution, in any meaningful sense of the term, of 0.5 A or 1.36 A. Such images can be obtained only because the specimens are periodic in two dimensions and have relatively small unit cell periodicities. With the same microscopes, the resolution, defined as the least distance between recognizable structural units of the specimen in nonperiodic array which can be clearly distinguished, is more like 2.6 8, or probably 3.0 to 3.5 8, with a goniometer specimen stage. Since for most electron microscopy of crystalline materials a goniometer stage is essential, it is this latter figure which represents the current microscope performance level for most applications in materials science. High Voltage Electron Microscopes. Resolution beyond these limits has been achieved only with microscopes using high voltages. Theoretical estimates have suggested that if the necessary levels of electrical and mechanical stability can be maintained and if the spherical aberration constant of the objective lens can be kept to within a few millimeters, the resolution should be improved by a factor of 2 or 3 if the voltage is increased from 100 keV to 1 MeV. The contrast of individual small objects and the thickness of specimens which can conveniently be used should also be improved by much the same factor ( 5 ) . Resolution approaching 2 A has already been demonstrated with the dedicated high resolution, high voltage microscopes in Japan. Apart from the Japanese efforts, special high resolution high voltage microscopes are being built in England and Germany (the latter with superconducting lenses). A proposal has been made that such an instrument should be imported for a projected high resolution microscopy research center in Berkeley, Calif. For other than high resolution applications, a n increasing number of operational high voltage microscopes is providing