Anal. Chem. 1992, 64, 407 R-428 R (444) Satow, T.; Machide, A.; Funakushi. K.; Paimieri, R. L. J . H@ Resolut. ChrOi?Wtogr.1991, 74, 276-9, (445) chrlstlensen, L.; Wher, T.; Hansen, D.; Brosse, J. M.; Le, G. J. Spectre 1090, 749, 35-8. (446)Tran, A. D.; Park, S.; Lisi, P. J.; Huynh, 0. T.; Ryail, R. R.; Lane, P. A. J . chrometogr. 1091, 542, 459-71. (447) MOsher, R. A. €kctr@wesiS 1990, 1 7 , 765-9. (448) Castagnola, M.; Casslano, L.; Rablno, R.; Rossetti, D. V.; Bassi, F. A. J . ChrometOgr. 1991, 572, 51-8. (449) Guhy, L. R.; London, J. E.; Valdez, J. 0.J . Chromatogr. 1991, 559,
431-43. (450) Jmic, D.; Zeilinger, K.; Reutter, W.; Boettscher, A.; Schmkz, G. J. chrometogr. 1900, 576, 89-98. (451) Nowicka, 0.; Bruenlng, T.; Qrothaus, B.; Kahl, G.; Schmkz, G. J . LlpM Res. 1990, 37,1173-86. (452) ’3ebauer, P.; Thonnann, W. J . Cbfomatogr. 1991, 558, 423-9. (453) Kajlwara, H. J. Chromatogr. 1091, 559, 345-56. (454) Kajiwara, H.; Hkano, H.; Oono. K. J. Blochem. Biophys. Methods 1991, 22.263-8. (455) Rush, R. S.;Cohen, A. S.; Karger, B. L. Anal. Cbem. 1991, 63, 1346-50. (456) Chen, F. T. A. J . Cbromarogr. 1991, 559, 445-53. (457) Chan, K. F. J.; Chen, W. H. Electrophoresis 1990, 7 7 , 15-8. (458) Ward, L. D.; Reid, G. E.; Moritz, R. L.; Simpson, R. J. J . Chromafogr. 1990, 579, 199-216. (459) Tanaka, H. W.; Kanbe, T.; Kalse, M.; Yamada, Y.; Semba, T. J. High Resohtt. Cbromatogr. 1901, 74, 491-2. (460) Meyw, H. E.; Hoffmann, P. E.; Korte, H.; Donella, D. A.; Brunati, A. M.; Pinna, L. A.; Couii. J.; Perich, J.; Valerio. R. M.; Johns, R. B. Chromato-
p@& 1980, 30, 691-5. (461) h g m a n , T.; Agerberth, B.; Joernvali, H. F€BS Lett. 1991, 283, 100-3. (482) Camlllerl, P.; Okafo, G. J . Chromatogr. 1901, 547, 489-95. (463) Okafo, G. N.; Brown, R.; Camilleri, P. J. Chem. Soc. 1991, No. 13, 864-6. (464) Okafo. 0.N.; Camlileri, P. J . Chromatogr. 1991, 547, 551-3. (465) Camilleri, P.; Okafo, G. N.; Southan, C.; Brown, R. Anal. Biocbem. 1991, 198, 36-42. (486) NaShabeh, W.; El, R. 2. J . ChrOmtOgr. 1991, 536. 31-42. (467) Kenndler, E.; Schmidt, B. K. J . Chromatogr. 1991, 545, 397-402. (488) Van de @W, T. A. A. M.; Janssen, P. S. L.; Van, N. J. W.; Van, 2. M. J. M.; Everaerts, F. M. J. Chromafogr. 1991, 545,379-89. (489) Vlnther, A.; Bjorn, S. E.; Soerensen, H. H.; Soeeberg, H. J . ChromatOgr. 1990, 576, 175-84. (470) Wenisch, E.; Tauer, C.; Jungbauer, A.; Katinger, H.; Faupei, M.; Righetti, P. G. J . C b f m t o g r . 1090, 576. 133-46. (471) Wu, S. L.: Teshima, G.;Cacia, J.; Hancock, W. S. J. Chromatogr. isno. .... 518. . .. 115-22. . __ (472) Wlktorowicr, J. E.; Wllson, K. J.; Shirley, B. A. Tech. froteln C h m . 4th 1990. 325-33. (473) Yim, K. w. J. chrometogr. i s s i , 559,401-10. Rickard, E. C.; Santa, P. F.; Sharknas. D. A.; S i m p (474) Nielsen, R. 0.; alam, 0.s. J. Cbfomatogr. 1991. 539, 177-65. (475) Rosenblum, B. 8. J. Llq. Cbromatogr. 1991, 74, 1017-24. (476)Cunico, R. L.; Gruhn, V.; Kresin, L.; Niteckl, D. E.; Wiktorowicr, J. E. J . ChrometOgr. 1991. 559, 487-477. (477) LW, K. J.; Heo, 0. S. J . CbrOfTWtOgr. 1991, 559, 317-324. (478) Thlbault, P.; Paris, C.; Pleasance, S. RapM Commun. M s s Spectrom 1981, 5, 484-90. (479) Metzger, J.; Jung, 0.f e p t b s 1990, 341-2. (480) Hoffstetter, K. S.; Paulus, A.; Gassmann, E.; Widmer, H. M. Anal. C I ” . 1901, 63. 1541-7. (481) Honda, S.; Makino, A.; Suzuki, S.; Kakehi, K. Anal. Blochem. 1090, 79 7 , 228-34.
(482) Honda, S.; Suzuki, K.; Kataoka, M.; Makino, A.; Kakehi, K. J . Chromet q r . 1990, 575, 653-8. (483) Carney, S. L.; Osborne, D. J. Anal. B k b e m . 1901, 195, 132-40. (484) Nashabeh. W.; El, R. 2 . J . Chrometogr. 1990,514, 57-64. (485) Lee, K. 8.; Kim, Y. S.; Linhardt, R. J. €lectropbores/s 1091, 12, 636-40. (486) Macek, J.; T)aden, U. R.; Van der Greef, J. J . Chromatogr. 1991, 545,177-82. (487) “ a n , A.; Cohen. A. S.; Helger, D. N.; Karger, 8. L. Anal. Chem. 1990, 62,137-41. (488) Beba, Y.; Matsuura, T.; Wakamoto, K.; Tsuhako, M. J. Cbromatogr. 1991, 558,273-84. (489) Pauius. A.; Ohms, J. I. J. Chfomatogr. 1990, 507, 1113-23. (490) Demorest, D.; Dubrow. R. J . Chromatogr. 1991, 559, 43-56. (491) Dubrow, R. S.Am. Lab. 1991, 23, 64-7. (492) Zhang, J. 2.; Chen. D. Y.; Wu, S.; Harke. H. R.; Dovichi, N. J. Clln. Cbem. 1091, 37, 1492-6. (493) Chen, D. Y.; Swwdbw, H. P.; Harke, H. R.; Zhang, J. 2.; Dovlchi, N. J. J . chrometogr. 1991. 559, 237-46. (494) Chen, J. W.; Cohen, A. S.; Karger, B. L. J. Chromatogr. 1991, 559, 295-305. (495) Cohen, A. S.; Naiarlan. D. R.: Karaer. B. L. J. chromatoar. 1990, 5’76. 49-60. (498) 516Swerdlow, 61-7 H.; Wu, S.; Harke, H.; Dovichi, N. J. J. Chromatogr. 1990,
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(512) Vinther, A.; Soeeberg, H.; Soerensen, H. H.; Jespersen, A. M. Ta&nta 1991, 38, 1369-79. (513) Banke, N.; Hansen, K.; Diets, I.J. Chromatogr. 1991, 559, 325-335. (514) Hebenbrock, K.; Meschke, H. E.; Schuegerl, K.; Friehs, K. BioTec 1991, 3,35-7. (515) Tsuji, K. J . Chromatogr. 1991, 550, 823-30. (516) Harrington, S. J.; Vano, R.; Li, T. M. J . Chromatogr. 1091, 559, 385-90. (517) Amankwa, L. N.; Scholl, J.; Kuhr, W. G. Anal. Chem. 1990, 62, 2189-93. (518) Chiari, M.; Ettorl, C.; Righetti, P. G. J . Chromatogr. 1991, 559, 119-31. (519) Righetti, P. G.;Ettori, C.; Chiarl, M. Electrophoresls 1981, 72, 55-8. (520) Jones, H. K.; Bellou, N. E. Anal. Chem. 1900, 62, 2484-90. (521) VanOrman, B. B.; McIntire, 0.L. Am. Lab. 1090, 22, 66-7. (522) Simonova, T. S.;Eremova, Y. Y.; KolioMn. Zh. 1900, 52, 901-8. (523) McCormlck, R. M. J . Llq. Chromatogr. 1991, 74, 939-52.
Kinetic Determinations and Some Kinetic Aspects of Analytical Chemistry Horacio A. Mottola* Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078-0447
Dolores PBrez-Bendito Department of Analytical Chemistry, University of Cdrdoba, 14071 Cdrdoba, Spain
This review retains, basically, the organizational structure of the revious one in this series (I). Topical itemization in the ‘dscellaneous” section is the only minor novelty introduced in this review and the kinetics of separation processes has now been included in that section. The papers reviewed
have been selected from those that appeared since November 1989 and that were available for the authors’ consideration through approximately November 1991. Professor Harry B. Mark, Jr., who since 1972 has been the senior author of these reviews, has decided to hand down this
0003-2700/92/036~407R~10.00/0 0 1992 American Chemlcal Society
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responsibility to us, and his name is no longer associated with this series. We dedicate this review to him in recognition of all his contributions to kinetics in analytical chemistry. By the time this review appears in print, the Fourth International Symposium on Kinetics in Analytical Chemistry will be close to taking place at the Institute of Physical and Theoretical Chemistry, University of Erlangen-Nuremberg, in Germany.
BOOKS AND REVIEWS Kinetic models for treating micellar catalysis are discussed in a book that examines organized assemblies comprised of surfactants and lipids and colloidal disperisons in inorganic solids (2). Chemiluminescence and photochemical detection under dynamic conditions and after chromatographic separation is the topic of a book edited by Birks ( 3 ) . Recent developments of analytical applications of chemiluminescence in solution have been reviewed (4). A very comprehensive coverage of luminescence determinations in chemistry, biology, and biomedicine has appeared as part of a series on practical spectroscopy (5). Hara and Tsukagoshi ( 6 ) reviewed chemiluminesce-based determinations of biolo ical species using metal-complex catalysis. An overview of c emiluminescence and bioluminescence with focus on clinical and biochemical applications has been presented by Kricka (7). Temporal resolution of events in the picosecond and even femtosecond range is of interest in contemporary analytical detection. A book on applications of time-resolved spectroscopic measurements (8)is a welcome addition to the literature. S ectroscopy on the ultrafast time scale (10 fs to 100 ps) has L e n reviewed by Wirth (9). Although this approach is not commonly employed in today’s analytical chemistry, the author discusses its future in chemical analysis. Redox mediation at electrode surfaces generates cycles in which chemical species are regenerated. A review on electron carriers in electroanalytical methods covering works selected from the literature up to 1987 has been presented (IO). A review of work mainly published in the Russian literature and on the application of catalytic polarographic currents in the analysis of water samples has been authored by Kheifeta and Zaitsev (11). The use of stopped-flow mixing in the study of reactions of analytical interest and in the application of analytical determinations has been reviewed (12). The review also discusses instrumental requirements. Rates in thermal analyses are of interest in material characterization; a concise review on thermal analysis discussea some dynamic aspects associated with the topic (13). Fluorescence time-resolved measurements for in vitro studies using lanthanide chelates have been briefy reviewed by Soini (14). The use of europium chelate labels for time-resolved fluorescence measurements has been reviewed (15).
fl
A. KINETIC METHODS FOR DETERMINATION OF CATALYSTS In the past 2 years, authors concerned with kinetics in analytical chemistry have followed a clear trend to w catalytic methods and automate existing approaches, many of which used flow injection methods. Table I summarizes the most salient contributions in relation to direct determination of catalysts. Many of the latest developments in catalytic systems are of great aid in designing new kinetic catalytic methods. Thus, the growing use of computers in the laboratory has dramatically facilitated the simulation, optimization,and automation of a number of catalytic determinations (A106). An optimization method for studying kinetic catalytic determinations based on the multiobject simplex procedure was developed and applied to two reactions involving Ag and Hg as catalysts that were monitored spectrophotometrically. The number of experiments required for the determination of these ions was reduced, and the apparent molar absor tivity was increased by 30-36% compared to that obtainefby singlefactor optimization (A107). The kinetics of the multistep catalytic degradation of a polymer to its constituent subunits was studied, and two methods for determining the concentration of each species were developed (A108). The continuous-addition-of-reagent technique was applied to catalytic-based determinations (A109) including that of 408R
ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992
copper by its catalytic effect on the oxidation of p,p’-dihydroxybenzophenone by hydrogen peroxide. The results revealed the method to be clearly superior to its conventional, earlier counterpart and to be suitable for the determination of copper in routine analyses involving samples such as serum. The performance of the amperometric and potentiometric techniques in the electrochemical monitorin of the kinetics of the iodide-catalyzed reaction between CehV) and As(II1) was assessed for analytical urposes (AIIO). Data collection and processing were done y a computer-based acquisition system. The results provided by various kinetic methods were discussed and compared. Potentiometric monitorin was hindered by the non-Nemtian behavior of the Ce(IV)/C!e(III) couple at both a platinum and a carbon paste electrode. On the basis of two methods for analysis of data from autocatalytic reactions taking place under pseudo-firsborder conditions (A11I), Schwartz developed a straightforward method for this type of data and for estimating statistical uncertainties in the rate constants thus calculated (A112). An uncomplicated method for the determination of primary and secondary aliphatic alcohols involving the use of a phase-transfer catalyst such as tetrabutylammonium hydrogen sulfate for the in situ formation of dithiocarbonates (xanthates) was reported (A113). A laboratory experiment based on the s t technique (A114) was used to identify trace amounts of &%I). The method relies on the catalytic effect of this metal ion on the reaction between Fe(II1) and thiosulfate. Antibodies have recently aroused much interest as catalysts for a variety of chemical and biochemical transformations. Their generic features and action on dissociative, associative, isomerization, photochemical, and redox reactions were recently reviewed (A115). Catalytic antibodies such as IgG were introduced as a major new class of biomolecules for molecular recognition in biosensors where the binding sites are continuously regenerated by the catalytic reaction of the substrate. This can be exploited to construct reversible immunobiosensors. Thus,a prototype potentiometric biosensor was made by modifying a micro-pH electrode with an antibody that catalyzes the hydrolysis of phenyl acetate, the H+ ions yielded being the monitored species (A116). The reversible response was linear over the range 20-500 pM, and the detection limit achieved was 5 pM. Micellar catalysis has a hi h potential for kinetic analysis. Thus, the rate of the Os(VII1f- and Cr(II1)-catalyzedreaction between Ce(1V) and As(II1) is increased by the presence of dodecyltrimethylammonium bromide (DTAB) micelles (A117). The two catalysts determined were found to affect the micellar catalysis similarly and no direct micelle-catalyst interaction was apparent. The micelle-catalyzed and the ion-catalyzed reactions occur in parallel, and the catalytic efficiency of each determines, under given conditions, the preferential route via which the reaction products are formed. The net result was an improved selectivity in the kinetic determination, but no significant gain in sensitivity in the analytical determination. An attempt at increasing sensitivity was made by studying the effect of micellar media on a catalyzed organic reaction ( A l l @ , the vanadium(V)-catalyzed oxidative coupling of p-phenetidine and catechol by bromate ion. The cationic surfactant cetylpyridinium chloride (CPC) was found to increase the reaction rate, which in turn resulted in an increase in the sensitivity of the kinetic determination of V(V) by 1order of magnitude. The mechanism by which vanadium acts on the reaction was elucidated, and the role of micellar media in catalytic kinetic methods was discussed (A118). Apparently the sensitivity can be increased only if the micelles act via a pathway other than that in which the catalyst is involved (e.g in the aforementioned V(V)-catalyzed reaction) or if the catalyst interacts directly with the micellar surface. This latter appears to occur where selenium catalyzes the decoloration of Methylene Blue (MB) by sulfide, which is accelerated by the presence of a nonionic surfactant such as Triton X-100. This finding was exploited for the kinetic spectrophotometric determination of selenium (A119). By virtue of its concentrating effect exerted through solubilization and absorption, the reactant concentration is substantially increased, as is the reaction rate to an extent dependent on the catalytic efficiency of the mixed micelles formed (MBTriton X-100) and the adsorbability of (S...Se)z- at the interface of the mixed micelles.
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KINETIC ASPECTS OF ANALYTICAL CHEMISTRY
H o r s c k A. Mattala is Professor and Head of the Chemistry Department, Oklahoma State University. He was bom in Buenos Aires, Argentina, and received his undergraduate and graduate education at the University of Buenos Aires. He earned Licenciate and Doctoral degrees from the University of Buenos Aires and did predoctoral work wkh Professor Ernest B. Sandell at the University of Minnesota (Minneapolis). He spent 2 years at the University of Arizona (Tucson) as a postdoctoral research associate in Professor Henry Freiser’s research group. After teaching for 2 years at the University of the Pacific (Stockton, CA), he joined OSU in the fall of 1967. His research interests include studies on the role of kinetics in analytical chemistry (including reaction rate methods), chemical immobilization of enzymes and chelating agents for use in reactors in continuous-flow systems, chemically modified electrodes for sensing in flow sytems. anatytical separations, and photochromism of metal chelates. He is the author of a monograph on “Kinetic Aspects of Analytical Chemistry”.
Dolores P 6 n ” M o is cwentty Professor of Analytical Chemistry at the University of Ctkdoba. Spain. She earned the Ph.D. degree in 1968 from the University of Seville, Spain. After 7 years as Assistant Professor at the University of Seville. she joined the Faculty of Sciences at the University of C W b a and since 1980 she has been a professor in the Department of Analytical Chemistry of this institution. Professor Pbrez-Bendlto’s research interests include trace analysis, molecular spectroscopy, and kinetic methods of determination with emphasis on differential rate methods and catalytic determinations with photometric and fluorometric monitoring. She has published extensively in these topics and is the coauthor of several textbooks and a monograph on “Kinetic Me* ods in Analytical Chemistry”.
Other applications of combined chemical and micellar catalysis include the determination of catalysts by an equilibrium method (A120, A121) that could be converted into an advantageous kinetic one. The analytical potential of this phenomenon for noncatalytic kinetic determinations has been shown by Koupparis et al. (A122),who developed a stopped-flow injection spectrophotometric method for the determination of hydrazines, hydrazides, amines, and amino acids based on the reaction between the analyte and l-fluoro-2,4dinitrobenzene,catalyzed by cetyltrimethylmonium bromide (CTBA). The method was applied to the determination of isoniazid, aspartane, and levodopa in commercially available pharmaceutical formulations (tablets). The surfactant was found to increase the sensitivity,as measured by the slope of the calibration graph, by a factor depending on the analyte concerned (e.g. the sensitivity for isoniazid was increased 28-fold). No explanation, however, was provided for the mechanism via which CTAB might act on the reaction rate. Some kinetic methods of analysis relying on electronic or numerical derivation of absorbance or fluorescence intensity with respect to time were also reported in the past two years. Chemical systems subject to an induction period (e.g. Landolt-type reactions) are among the few to which such derivative techniques are applicable. In this context, the analytical performance of the electronic derivation approach was assessed on the determination of iodide, Fe(II), molybdenum, and tungsten as catalysts for different indicator reactions by using the peak height of the second derivative (A123, A124). The increased accuracy and precision of the electronic derivation technique results in lower detection limits than in conventional kinetic methods. A quite slective empirical data-processing method based on numerical differentiation by use of the Savitzky-Golay algorithm was also reported (A125). The method involves parameters not directly related to the initial rate, but similar to those employed in derivative spectrometry (e.g. the distance between two peaks or the value of the derivative at a single time). The nth-order derivative curves obtained for the Cu(I1)-catalyzedhydroquinone-H202system and the Fe(I1)-induced pyridoxal-2-pyridylhydrazone-H202
system-both of which exhibit an induction period-testify to the substantially increased selectivity achieved in the determination of the metal ion concerned. Several methods for the kinetic determination of hydrogen peroxide both as catalyst and as substrate of different reactions have been reported. Thus, H202acts as a catalyst for the alkaline hydrolysis of aspirin, which is the basis for the kinetic spectrophotometric determination of this substance, by monitoring of the absorption at 290 nm of the salicylic acid produced at pH 10.5-11.0 (A126). The time required to perform each determination is 5-7 min and the limit of detection for H202is l X M. The method was applied to the determination of hydrogen peroxide in natural waters and was also subsequently employed in conjunction with a complexation reaction involving indophenol [determination limit (2.0 f 0.1) X MI, and with the Fe(II1)-catalyzedoxidation of o-dianisidine by IO4- in the presence of 2,2’-bipyridyl [determination limit, (2.7 f 0.7) X lo* MI (A127). Only one method for the kinetic determination of H20 as a substrate (oxidant) of a catalyzed reaction was reportec! in the last 2 years. It is based on the Fe(I1)-catalyzedoxidation of benzoic acid by H202,which yields hydroxylated products (OHBA) that are detected by fluorescence techniques (A128). This new Fenton-OHBA method was applied to the analysis of atmospheric samples and has the advantage of using inexpensive, stable, readily available chemical reagents that require no refrigeration, in contrast to the widely used enzymatic (p-hydroxypheny1)aceticacid method. The new approach is insensitive to the fairly low transition-metal concentrations often occurring in atmospheric samples. The calibration graph obtained was linear over the H202concentration range 10-8-10-5 M, and the detection limit was 2 X M. A series of papers on the use of a mimetic peroxidase/ metalloporphyrin complex/ homovanillic acid/H202fluorescent system for the determination of hydrogen peroxide was published between 1989 and 1991. By way of example, the kinetic figures of merit of the method based on the chelate of Mn(II1) with a,@,y,b-tetrabis(N,N,N-trimethy1ammonio)phenylporphyrin [Mn-T(4-TAP)P] are comparable to those of the method using horseradish peroxidase (HRP). Also, the method allows the convenient determination of H202 at concentrations down to 2.64 X M (A129). Replacing the previous chelate with the manganese tetrakis(sulfopheny1)porphyrin complex (Mn-TPPS,) allowed H202to be determined over the range 8.5 X to 2.5 X lo* M (A130). Other metalloporphyrins [Me-P, with Me = Mn(III),Fe(III), Co(III), Rh(III), and Pt(IV)] were also tested and their catalytic behavior compared with that of HRP in both enzymatic and kinetic determinations. As a result, a kinetic method for the determination of H202and traces of glucose in serum was developed (A131-AI33). Also, several methods for the determination of hydrogen peroxide based on different Mnporphyrin complexes and monitoring of the fluorescence of the ~-tyrosine/H~O~ system (A134),and on the chromogenic reaction of H202with 4-aminoantipyrine and phenol were reported (A135-AI37). Although most of these methods are not strictly kinetic in nature-measurements are made after a few minutes, once the analytical signal has stabilized-they warrant inclusion here because they could be transformed into kinetic methods with presumably appealing advantages. Very few kinetic determinations for substrates other than those mentioned above were reported in the reviewed period. In fact, only the determination of sulfite based on the oxidation of hydrogen sulfite to hydrogen sulfate by dissolved oxygen, catalyzed by 1,2,3,4thiazole-5-thiolate ion (AI%), and the continuous-flowdetermination of reserpine by oxidation with IO4-, catalyzed by Mn(II), were contributed in this context (A139). The determination of sulfite was done by monitoring the absorbance decrease at 313 nm (the observed rate coefficient, kob,was used as a measure of the sulfite concentration). The analyte was determined over the range 1.0 X to 1.0 X M at pH 7. On the other hand, the determination of reserpine was accomplished by monitoring the formation of its oxidation product at 385 nm. The method was applied to determine the analyte in pharmaceutical tablets. A relatively large number of kinetic methods for the determination of anions catalyzing various indicator reactions were contributed in the past two years. Thus, fluoride ion ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992
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KINETIC ASPECTS OF ANALYTICAL CHEMISTRY
Table I. Determination of Different Catalytic Species by Kinetic Methods Based on Primary Effects
species
indicator reaction
dynamic range or detection limit, ng/mL
chromium 1-naphthylamine + H202
+ H202 Bromophenol Red + H202
phenosafranin cobalt
Celestine Blue
copper
0-160
catalyzed by Cr(V1); photometric monitoring at 490 nm; pH 4.3 and T 80 O C ; RSD = 9.6% ( n = 10); fixed-time method (5 min) catalyzed by Cr(V1); photometric monitoring; HOAc/NaOAc buffer phoulmetric monitoring; ammonia buffer
0-42
photometric monitoring in an alkaline medium; use of rate constants to construct the calibration graph photometric monitoring
=
0-200
+ H202
diphenylcarbazone + dissolved atmospheric oxygen decomposition of Amido Black 10B by H202
comments
5-30
photometric monitoring; tiron used as activator; calibration graph of the form In (A1/&) vs [Co], where A, and & are absorbances at 1 and 6 min, respectively 1-amino-8-hydroxyl-[ @a few ng/mL photometric monitoring; tiron used as activator; hydroxyphenyl)azo] -3,6-naphother derivatives of thalenedisulfonic acid + H202 l-amino-8-naphthol-3,6-disulfonic acid tested; dyes with electron-releasing groups most sensitive reagents; same kinetic procedure used as in A6 carminic acid + H202 3.2 X photometric monitoring; Clark-Lubs buffer of pH 9.8; apparent activation energy, 70.25 kJ/mol; RSD = 3% hydroquinone + resorcinol + 4 x 10-1 reaction activated by ammonium ion; photometric monitoring at 485 nm; selectivity H202 improved by using a 2-thienylformylfluoroacetone/ benzene mixture 3-hydroxybenzaldehyde azine t 0.5-18 photometric monitoring at 465 nm; the method virtually specific for copper; ammoniacal K2S206 medium; initial-rate method; a plausible reaction mechanism for the catalyzed reaction put forward phenolphthalein + H202 0-12 photometric monitoring at 555 nm in a 0.1 M EDTA medium of pH 9.0 no interference from any of most common foreign ions; 40-fold excesses of Mn0,- tolerated trinitrobenzenesulfonate + S2103 to 3.0 x io' potentiometric monitoring by use of a trinitrobenzenesulfonateion-selective electrode; variable-time method; poor selectivity; method applicable to determination of carbohydrates; electrode also useful for determination of rate constants and activation energies Methylene Blue + H202 0-28 photometric monitoring; the activation energies of the catalyzed and uncatalyzed reaction were measured Rhodamine B + H202 0.008-2.4 (phot.) photometric and fluorimetric monitoring of 0.06-3.3 (fluor.) decoloration and decreasing fluorescence in an NH3-NH4F medium of pH 9.0; relative error less than 4.0% in both methods cysteine + O2 0-70 oxygen bubbled through an 02-saturated 60% DMF solution of Cu(I1) and cysteine for exactly 20 min; EDTA added to stop reaction and remaining cysteine determined photometrically with 2,2'-dithio-bis(5-nitropyridine) morin + H202or dissolved 0-10 (HzOz) photometric monitoring of absorbance decrease at atmospheric O2 0-140 (02) 409 nm; several kinetic methods applied oxidation of ferrocene 4 x 106 to 3 x 106 spectrophotometric determination with 1,lO-phenanthroline of Fe(II1) formed in oxidative decomposition of ferricenium ion hydroxylamine + dissolved 50-500 thermometric monitoring; initial-rate method; atmospheric O2 only serious interference posed by Fe(III), but can be overcome by using citrate p-hydroxyphenylglycine + photometric monitoring at 410 nm (pH 6-9) or at 520 nm (pH 1));an alternative method based H202 on the aerial oxidation of an azo derivative of the organic reagent also applied eosin + H 2 0 2 0.2-20 photometric monitoring of absorbance decrease at 515 nm and 90 0.2 "C in an NH3.H20-NH,CI buffer of pH 9.2 Briggs-Rauschen type new oscillating reaction between H20z/I03-, oscillating system malonic acid and Mn(I1) in acid medium; determination based on the final oscillating time; potentiometric monitoring with a Pt and an iodide electrode; the reaction catalyzed also by Cr(V1) and V(V)
*
410R
ANALYTICAL CHEMISTRY, VOL. 64. NO. 12, JUNE 15, 1992
type of sample
ref
river water containing industrial A1 Waste steel
A2
high-purity materials [NiCI,. Ni(NOA1 vitam'in BiZ-kter mineralization with KHSO,
A3
Chinese herbal medicines
A5
nickel chemical reagents
A6
A4
A7
river water; tea leaves; vitamin BIZ
A8
water, industrial wastewater; soil A9
drinking waters, wines, meats; alloys; brass plating baths
A10
waters
All
A12
biological samples
A13
human hair; aluminum and magnesium alloys
A14
A1L
A16 A17 waters
A18 A19
tap water; pure aluminum and aluminium alloys; pure NaCl
A20 A21
KINETIC ASPECTS OF ANALYTICAL CHEMISTRY
Table I (Continued)
indicator reaction
species iodine
dynamic range or detection limit, ng/mL
Ce(1V) + As(II1)
2-60
Ce(IV) + As(II1)
+ As(II1)
hexacyanomanganate
0.2
4,4’-bis(dimethylamino)diphenrl- 0 - 2 methane + chloramine T
iridium iron
1-naphthophthalein + IOL Methylene Blue
20
+ H20z
0.04-12
Rhodamine B + H202
0.04-150
decomposition of H202
0.5-273
2,6-dihydroxynicotinic acid HZ02
+
Dimethyl Yellow + H202 sulfanilic acid Neutral Red
+ NaI04
+ H2OZ
citrate + IO,‘ Thymol Blue
0-28
50-220 0-28
0.01-55.8
+ H202
hydroxylamine t dissolved atmospheric O2
0-3.2 10-500 3.5-150
lead
Alizarin Violet + K2S208
manganese Acid Chrome Blue K Ce(1V) + Iz
+ H202
salicylaldehyde + H202 Rhodamine B + KIO, sulfanilic acid
+ NaI04
dithionate + chloranilate
tiron
+ H202
oxidation with IO;
Cal-Red
+ H20,
0-1500 (initial-ratel e300 (fixed-time)
comments fluorimetric monitoring of formation of Ce(II1) at 360 nm (excitation at 260 nm); stopped-flow technique used to obtain wider linear calibration range and a higher throughput (120 samples/h); method compared with conventional kinetic counterpart modified Watkinson method for photometric determination of iodine in iodized eggs; RSD = 4.3-7.9% iodine exerts a promoting effect rather than a catalytic effect since Mn(1V) oxidizes iodide to inactive iodate; photometric monitoring at 387 nm; several species interfered flow injection spectrophotometric determination; 85 samples/h for an injected volume of 300 rL; RSD = 0.8-2.8%; iodine and iodate (at high concentrations) have same effect as iodide and must be removed with thioacetamide flow injection spectrophotometric method; 61 samples/h photometric monitoring of absorbance decrease at 668 nm in presence of 1,lO-phenanthroline as activator photometric monitoring at 560 nm; reaction accelerated by KSCN; fixed-time method (12 min) method based on the catalase-like activity of the [(trien)Fe(OH)2]+complex; fixed time method (2 or 5 min); several metal ions tolerated in 8-16-fold excesses; Mn(I1) interferes seriously photometric monitoring; reaction is catalyzed also by Cu(I1) and by V(V) if bromate is used instead of H2OZ;all three metal ions can be determined in presence of one another by using F to mask Fe(II1) photometric monitoring at 515 nm; highly selective method direct-injection thermometric method; 1,lO-phenanthroline used as activator; RSD = 6.6%; good selectivity photometric monitoring; fixed-time method (15 min); recoveries of 96.6% (rice) and 98.8% (flour) redox reaction induced by Fe(I1); potentiometric monitoring with periodate-selective electrode; citrate acta as both reductant and activator photometric monitoring; 2,2’-bipyridyl acts as activator catalyzed by the Fe(II1)-EDTA complex; thermometric monitoring; EDTA endows method with sensitivity and selectivity same as previous method but with photometric monitoring at 542 nm; flow injection technique photometric monitoring; several metal ions interfere but can be removed by masking
photometric monitoring at 575 nm; RSD = 5.9% redox reaction catalyzed by concurrent Mn(I1) in the presence of Cr2072-;iodine generated from KI, which is rapidly oxidized by Ce(IV) photometric monitoring at 500 nm; RSD = 1.2% 5-100 0.047-5.6 fluorimetric monitoring; 1,lO-phenanthrolineused as activator; pH 2.4 160 to 2.4 x lo3 very selective direct-injection thermometric method 500 to 5 X lo3 potentiometric monitoring with chloroanilate liquid membrane ion-selective electrode; RSD = 1 4 % ; variable-time method no sample pretreatment required in the absence of Cu(I1) and Cd(I1) flow injection method with photometric monitoring 5.5-38.4 using gradient dilution and stopped-flow mode; 40 samples/h; highly selective; RSD = 5.5% ( n = 6) 300 photometric flow injection method based on formation of permanganate; autocatalytic effect of Mn(I1) is enhanced by a permanganate confluent stream that accelerates reaction photometric monitoring of absorbance decrease at 0-8 630 nm; sensitive and quite selective, but subject to interference of V(V) 0-2
type of sample
ref
pharmaceuticals; table salt; milk A22
high-iodine eggs
A23
reagent-grade sodium arsenite: table salt
A24
natural waters; distilled and redistilled water
A25
A26 natural waters; reagent-grade HCI
A27
natural (river and lake) waters
A28 A29
lake water
A30
water; human hair and fingernails
A31 A32
flour and rice
A33
tap water
A34
natural and distilled water; chemicals water, beer, wine
A35 A36
water and wine
A37 A38
silicate minerals
A39 A40
natural waters natural waters; human hair; Mg alloys multivitamin complex
A41 A42
industrial seeds
A44
natural waters
A45
soils, plants, and rocks
A46
3 x 104 to 10”
ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992
A43
A41
411A
KINETIC ASPECTS OF ANALYTICAL CHEMISTRY
Table I (Continued)
species
indicator reaction photoactivated oxidation of S032-+ Rose Bengal (photosensitizer) oxidative coupling of 3-methyl2-benzothiazolinone hydrazone with NJN-dimethylanilinc by H202 Brilliant Green + KIO, N-methyldiphenylamine-4sulfonic acid + KIO, N,N-diethylaniline Malachite Green
mercury
+ KIO,
+ KIO,
dynamic range or detection limit, ng/mL
drinking water
A48
2-30
flow injection method with photometric detection at 590 nm; 1,lO-phenanthrolinc a n d citrate used BS activators; 10 samples/h photometric monitoring at 460 nm photometric monitoring; 1,lO-phenanthrolinc IS used as activator; relative error 55-8% (without thermostating) flow injection method with in-valve ion-exchange preconcentration microcolumn; up to 15 samples/h flow injection stopped-flow method with photometric detection using nitrilotriacetic acid as activator; RSD arabinose > galactose > xylose > glucose, which is consistent with their power to cam oscillations in their Mn(II)-catalyzed reactions with bromate. The reaction rate constants for the Br2-Mn(III), Brz-saccharide, Mn(III)-saccharide, and Mn(111)-Br- systems were calculated (the former two were much smaller than the latter). The kinetics of the potentially oscillatory reaction between oxalic acid and permanganate was studied by Keki and Beck (On, who concluded that it meets the mechanistic criteria for oscillating reactions. However, the measured oscillatory changes in the absorbance were found to arise from the formation of colloidal and coagulated MnOz rather than from chemical events. Phosphomolybdenum blue complexes were among the systems whose formation kinetics were most frequently studied in this context. Thus, the effect of the acidity and molybdate concentration on the kinetics of formation of the phosphoantimonyl molybdenum blue complex were examined (08).The [H+]/[Mo]ratio was found to be a crucial parameter that not only influences the form of the final reduced complex, but also plays a key role in controlling the reaction kinetics. The study was aimed at determining the optimum conditions for the flow injection determination of phosphate by the phosphoantimonyl molybdenum blue method. Below are some comments on the kinetics and/or mechanism of reactions catalyzed by transition metal ions and noble metals, some of which involve the decomposition of HzOz and/or are of biological interest. Reactions Catalyzed by Transition Metal Ions. Manganese(E1) is known to be oxidized to Mn(II1) by Cr(V1) in the presence of excess oxalate, with which it forms a com lex This consecutive reaction pathway, however, had not yet !een studied. The kinetics of the Mn(II)-cataly& reaction between chromic acid and oxalic acid was recently studied to elucidate such a pathway (09). The absorbance of the mixture of Cr(VI), oxalate, and Mn(I1) at 480 nm was found to increase with time to a maximum, after which it decreased. This variation was ascribed to the consecutive steps k,
A-I-C
k~
The maximum absorbance was directly roportional to [Cr(VI)l0;also, while k, varied with [Mn(IIYloand [C2042-]~, k,
KINETIC ASPECTS
was not affected by the former concentration. The paths represented by k, and k, were proposed to account for the experimental resulta obtained. The inhibition of the peroxidase-like activity of manganese tetrakis(sulfopheny1)porphyrin (Mn-TPPS4) by pyridine and some other substances was examined in the fluorescence reaction between homovanillic acid and H202, and the inhibitory effect of the spin-trapping species was found to be irreversible (010).The constanta for the competitivelylinear reversible inhibitors pyridine and o-chlorophenol were determined by applying the Michaelis-Menten equation with H202as substrate. The mechanism for the peroxidase-like activity of Mn-TPPS4 was found to be analogous to that of the reaction between chavicol and hydrogen peroxide, catalyzed by Mn(11)-tetrakis [4-(NJVJV-trimethylammonium)phenyl]phorphyrin [Mn-T-(4-TAP)P], which proceeds as follows (01I): k
MP
+ Hz02& (MP)S + H 2 0 k2
(MP)S + AH (MP)S’
+ AH A* + A*
(MP)S’ + A* MP
-
+ HzO + A*
k7
A-A where MP is a peroxidase-like metalloporphyrin such as Mn-T-(4TAP)P, AH is a substrate such as chavicol, and (M)S and (MP)S’ are the enzyme-substrate complexes formed in the process. Chavicol was proposed as a new substrate in conjunction with H202 and horseradish peroxidase for the catalytic fluorescence determination of blood glucose (012). The Fe(I1)-catalyzed oxidation between copper and another metalloporphyrin, viz. meso-tetrakis(4-methoxy-3-sulfopheny1)porphyrin was studied and used for the determination of iron at the nanogram per milliliter level (013). Some reactions involving Fe(III) complexes as catalysts were also investigated. One such reaction was the decomposition of Hz02catalyzed by the Fe(II1)-diethylenetriaminepentaacetate complex (Fey), the rate law of which was found to be given by (014)
[FeY(OH)2-[OOH]-
k2
[H+l
where kl and k2 were obtained at different temperatures. A substitution-controlled mechanism was proposed to account for the formation of the violet peroxy intermediate. The results were compared with previously reported data for the Fe-EDTA complex, which differs in its overall anionic charge as a result of its different number of negatively charged carboxylate groups. Thii supposedly influences the readiness with which the complexes can undergo substitution by nucleophiles such as HOO- or its conjugate acid. The catalytic behavior of the Fe(II1)-8-quinolinol complex in the chemiluminescence reaction between luminol and hydrogen peroxide in reverse micelles was studied (015). Uptake of the complex by the micelles and its subsequent decomposition within them apparently take place very readily. New contributions to the study of the arene hydroxylation mechanism based on observed kinetic regularities in the oxidation of monosubstituted phenols by Fenton’s reagent were reported by Mitnik et al. (016). A scheme for the process was proposed to account for the stepwise conversion of Fe(1II) (the catalyst) into various complex forms. The reaction appears to take place in the coordination sphere of Fe(II1). The nonenzymatic conversion of adenosine diphosphate (ADP) into adenosine triphosphate (ATP) was found to occur readily in the presence of Fe(III) and acetyl phosphate (017). This is of great biological interest, yet it remains unclear how Fe(II1) ions catalyze the phosphorylation of ADP. A comprehensive study of the decomposition kinetics of 1-meth 1-1-phenylethyl hydro eroxide (cumene hydroperoxide, 8HP) catalyzed by Co(& naphthenate was reported (018).a-Cumyl alcohol, acetophenone, and di-a-cumyl peroxide were obtained as decomposition producta at 25 OC. Both
OF ANALYTICAL CHEMISTRY
the disappearanceof CHP and the formation of each product were studied kinetically. Kinetic evidence for the occurrence of an intermediate in the H (11)-catalyzed formation of metalloporphyrins was reporte~! by Tabata and Miyata (019). The heterodinuclear metalloporphyrin including mercury(I1) [and Zn(II)] was kineticall determined to react via a two-step pathway, as confiimedrby the rate equation obtained and the changes in the absorption spectrum on reaction of Hg(II)-porphyrin with aquo zinc(I1). Schiff base formation reactions between aromatic aldehydes and o-dianisidine in the presence of acetic acid and SnC14as catalysts were also studied kinetically (020). Two of three possible pathways for these reactions are catalyzed by the acid and the other by the stannic chloride. In the SnCh-catalyzed pathway, the aldehyde seems to be first complexed b the chloride and then attacked by a 2:l o-dianisidine-&C14 complex to form a carbinolamine that subsequently forms the final reaction product. The rate law for this mechanism was found to be consistent with experimental resulta. Some analytical implications of the kinetics involved were discussed. Finally, the Se(1V)-catalyzedoxidation of -hydrazinebenzenesulfonic acid to its diazonium ion anfsubse uent conversion into a yellow azo dye by couplin wiA mphenylenediamine was studied by Lin and Ding f021), who concluded that only part of the diazonium salt produced is coupled to form a measurable colored dye and that chloride ion is involved in the redox reaction between Se and C10 -, which is required for the catalytic cycle of selenium to &e completed. Reactions Catalyzed by Noble Metals. The Ag(1)-catalyzed oxidation of the tris(1,lO-phenanthro1ine)-Fe(II1) complex by peroxydiphosphate (pdp) was studied kinetically by monitoring the disappearance of the complex at 510 nm (022), and a mechanism accounting for the determined rate law was proposed. Silver appears to exert its catalytic effect through a complex with pdp, for which water and Fe(phen)P also compete. The Ag(1)-pdp complex undergoes an intramolecular conversion to a Ag(I1)-pdp complex that finally interacts with the substrate in the rate-determining step of the process. The kinetics and mechanism of various ruthenium-catalyzed reactions of analytical interest were also studied. One such reaction was the oxidation of the hydroxy acids tartaric, lactic, malic and citric by N-bromosuccinimidein a perchloric medium containing mercuric acetate (023). The reaction rate is first order in the oxidant and zero order in the substrate; it is decreased by H+ ions and increased by low Ru(II1) concentrations, but independent of the ruthenium concentration at higher concentrations of this catalyst. A mechanism consistent with the kinetic results obtained was proposed. The kinetics and mechanism of the oxidation of triphenylphosphine (PPh3) by potassium hydrogen mono eroxysulfate in a water-dioxane medium, which is c a t a y lz dby aquo ro lenediaminetetraacetatoruthenate(II1) [PDTAR U ~ I & ~,was ~ ~ studied ;by Khan et al. (024). The kinetics of oxygenation of this complex (complex 1)to [ (PDTA)Ru’(O)]- (complex 2) by KHSOs were studied photometrically by monitoring the appearance of the characteristic oxo peak at 393 nm and pH 6.0. The time course of the oxygen atom transfer from complex 2 to PPh3 was also investigated. Activation parameters for both reactions were calculated and a mechanism was proposed. Ruthenium(I1) complexes containin 2,2’-bipyridine and 2,2’-bipyrazine catalyze the photoinducefoxidationof ascorbic acid to hydrogen peroxide by molecular oxygen (025). The formation of Hz02and the disappearance of ascorbic acid were monitored polar0 a p h i d y during continuous irradiation of the reaction megum with visible light. The [ R u ( b ~ z ) ~ ] ~ + complex (bpz = 2,2’-bipyrazine) was found to be the most efficient photocatalyst of the four Ru(I1) complexes tested. Ruthenium red, a di-p-oxo-bridgedruthenium complex, and its oxidized form, ruthenium brown, were assayed as potential hom eneous redox catalysts for the oxidation of water to O2 by CeyIV)in sulfuric and perchloric acid (026). In both media, Ce(1V) oxidizes ruthenium red to ruthenium brown, which is decomposed irreversibly by excess cerium to producta that yield three weak absor tion bands at 390,523, and 593 nm. Only in HC104 do the fecomposition products appear to act as a stable catalyst for production of 02.Spectral evidence ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992
417R
KINETIC ASPECTS OF ANALYTICAL CHEMISTRY
suggests that the active catalyst may be a hydrolyzed polymeric Ru(1V) species. The rate of the catalyzed reaction is roportional to the initial concentration of ruthenium red or rown. Reactions Catalyzed by Other Species. As noted earlier, Schiff base formation reactions between aromatic aldehydes and o-dianisidine catalyzed by acetic acid may proceed via two different pathways (020). One of them involves the reaction of the aldehyde with a solvated proton, i.e. in specific acid catalysis. Depending on the acidity of the medium, free or monoprotonated o-dianisidine attacks the carbonyl carbon to form a carbinolamine intermediate that is then dehydrated to the final product. One other acid-catalyzed reaction worth mentioning in this context is the oxidation of 2,4-dichlorophenoxyaceticacid (2,4-D) by ammonium nitrate in an aqueous medium, the kinetics and mechanism of which were studied by Leavitt and Abraham (027),who determined the kinetic constants involved from a proposed pathway involving the simultaneous oxidation of 2,4D and decomposition of the oxidant by best-fit analysis of the results. They used the determined rate expressions to develop a mathematical model that was employed to calculate the temperature at which the conversion of 2,4-D would be maximal. Finally, the fluorescence of the Ltyrosine/HzOz/horseradish Deroxidase svstem was also investigated. Although tvrosine does not behive exactly like homo&nillic acid as mbstrate for peroxidase, both could be determined enzymatically over the same concentration range and with identical sensitivity, so the former can indeed replace the latter for this purpose. In fact, one immediate a plication was the determination of glucose and tyrosine in uman serum (028).
E
K
E. KINETIC DETERMINATIONS BASED ON ELECTRODE REACTIONS AND PROCESSES AND ASSOCIATED KINETIC ASPECTS Above a given applied potential the response at some chemically modified electrodes has been observed to be smaller than at the corresponding unmodified one ( E l ) . This behavior has been kinetically explained by considering that the modifer provides a chemical path that competes with the normal response at the surface. Electrocatalysis at galvanostatistically pretreated (treatment at controlled anodic current for a few minutes followed by treatment at controlled cathodic current) glassy carbon electrodes has been studied (E2). The studies were conducted in presence of catechol, hydroquinone, and ascorbic acid. Jiang and Dong (E3)examined the electrocatalytic behavior of HzOZoxidation at a cobalt protoporphyrin-modified pyrolytic graphite electrode. The effect can be used for the determination of HzOz at the M level. Hexacyanoferrate ions do not act as electrocatalysts, and the current response is smaller a t the pretreated surfaces. The electrocatalysis is described as resulting from adsorption of the analytes and the presence of oxygen-containing electrocatalytic centers on the pretreated surface. Conclusions are based on cyclic voltammetric, chronoamperometric, chronocoulometric, scanning electron microscopic, and X-ray photoelectron spectrometric studies. The response of low-surface-area electrochemical sensors has been observed to be kinetically controlled (E4). This was concluded as part of a study of NO reduction at gold electrodes with differing geometries. T i e rate-controlling step was proposed as NOz/Au(adsorbed) NO(g) + AuO(s)
-
that completes the catalytic cycle coupled to the following electrode process: AuO(s) + 2 H++ 2e- Au(s) + HzO(l) Applications, in continuous-flow systems, of electrodes modified by ruthenium containing polymers have been discussed by Barisci et al. (E5). The complex described in the paper is [ R U ( ~ ~ ~ ) ~ ( P V P ) where ,C~]C bpy ~ , = 2,2’-bipyridyl and PVP = poly(4-vinylpyridine); it was applied to a glassy carbon surface in the form of a methanolic solution that was allowed to dry in the dark. The surface did not exhibit long-term stability when used for detection of nitrite ion and various dithiocarbamate metal complexes. Satisfactory detection was achieved, however, within the same day of preparation. Electrocatalysisat fiis made from clay colloids and 418R
ANALYTICAL CHEMISTRY, VOL. 64, NO. 12, JUNE 15, 1992
dialkyldimethylammonium surfactants with incorporated metal phthalocyanine mediators has been reported (E6). Stable catalytic currents were observed for a t least ten days after film preparation in the reduction of trichloroacetic acid. Pilocarpine (2.5 X to 8.0 X lo4 M) can be determined by means of an induced catalytic polarographic prewave of nickel(I1) ( E n . A mechanism for the electrode reaction was proposed and the differential-pulse polarographic determination of pilocarpine described. The feasibility of determining molybdenum down to 6 X pg/mL by using the Br03catalytic wave that develops in the Mo(VI)/pyrocatechol BrOy system has.been demonstrated by Toropova et al. (E8{ Vakhobova et al. (E9)have investigated the effect of ultrasonic vibrations on the catalytic polarographic waves of hydroxylamine in the presence of the complexes of Mo(V1) and W(VI) with pyrocatechol. The interference of molybdenum in tungsten determination is suppressed in the Mo:W ratio range of 1:l to 1:3. Determination of titanium(1V) at picomolar levels (limit of detection about 7 pM) has been made exploiting the catalytic effect of chlorate on the electrochemical reduction of titanium(IV) (EIO).The effect enhances the sensitivity of titanium determination by cathodic strip ing voltammetry and makes the approach applicable to anJysis of river water for titanium. Saraswathi et al. ( E l l )determined chromium at microgram per milliliter levels using a catalytic current developed at a droppin mercury electrode and due to Cr(V1) in the presence of sor!ium pentamethylenedithiocarbamate (ammonium chloride/ammonia buffer, pH 8.00). The method was applied to the determination of chromium in Ocimum sanctum leaves and stainless steel. The polaroaphic determination of 2-mercaptobenzothiale (104-10-5 , an electrochemically inactive species that in presence of Co(II) produces a catalytic hydrogen wave, has been described
5)
(E12).
Magyar et al. (E13) described a differential- ulse polarographic method for the determination of W(V$using a catalytic adso tion wave. The complex formed by W(V1) and 7-iod~&%hy~oxyquinoline-5-sulfonic acid at pH 0.5 is strongly adsorbed on Hg(1). The adsorbed complex is reduced by the polarographic current and oxidized very fast by hydrogen ions. Since the redox process takes place within the double layer, the process is not diffusion limited and enhanced currents are observed. The limit of detection is reported to be at the M level. Molybdenum(V1) interferes seriously and requires separation from W(VI). The rate of anodic stripping evolution deposited on a gold electrode (IO, I- system) has E i r u y t o determine Hg(I1) in the 0.4-1. pg/mL range
6
(E14). Copper oxide particles in a carbon paste preparation have been used for the amperometric detection of carbohydrates, amino acids, aliphatic diols, alcohols, amines, and alkyl POlyethoxy alcohol detergents (E15).Electrocatalysis is operative in the detection process.
F. APPLICATIONS OF LUMINESCENCE There is no exaggeration in stating that luminescence-based methods, involving measurements under dynamic conditions, have experimented a radical increase in use in the past two years, to which the content and coverge of this section testify. The December 1,1989, issue of Analytica Chimica Acta ( F l ) was totally devoted to the Proceedings of the 3rd International Symposium on Quantitative Luminescence Spectrometry in the Biochemical Sciences. Most of the papers in this issue are of analyticalinterest with kinetic implications. The inaugural issue of the Journal of Fluorescence appeared in March 1991 with Joseph R. Lakowicz as Editor-in-Chief and Susan M. Rinehart as Assistant Editor; the journal is published by Plenum Press. Nakashma et al. (F2)have synthesized eight aryl oxalates each containing an alkoxy grou and evaluated them as reagents in peroxyoxalate chemiruminescence. Bis[2-(3,6dioxaheptyloxycarbonyl~-4bromophenyl] oxalate provided the highest chemiluminescence intensity. Kinetic information on the chemiluminescence emission produced during the hypochlorite oxidation of some tertiar amines in presence of Rhodamine B he^ been reported (17351 The information is part of a paper describing the determination of a nonionic surfactant in aqueous environmental samples by a continuousflow procedure. Mechanistic pathways describing the quenching of peroxyoxalate Chemiluminescenceby substituted
KINETIC ASPECTS
amines have been discussed (F4). No evidence for amine quenching of fluorescence was found. The quenching of the response can be utilized to determine amines but, as is generally the case for determinations based on inhibitions, the linear range of calibration curves is limited. Manganeae tetrakis(sulfopheny1)porphine increases the rate of oxidation of luminol by HzOzand this permits the determination of HzOzand glucose at limits of detection quoted as 5.5 X 1O-eand 2.7 X lo4 M, respectively ( F a . The behavior is compared with that of horseradish peroxidase, for which the manganese complex behaves as a mimetic enzyme. Cationic micellar hexadecyltrimethylammoniumhydroxide and nonionic micellar polyo ethylene(23)dodecanolenhance the light emission producedTy the reaction of lucigenin with catecholamines (3'6). These improve the limits of detection for catecholamine as much as 10-fold. Room-temperature phosphorescence on solid supports continues to receive attention. Caffeine and theophylene have identical room-temperature phosphorescence emissions but caffeine can be extracted into chloroform from aqueous phase at pH ca. 9.0; the two phases can then be analyzed by roomtemperature phosphorescence on Whatman No. 1fiter paper &9 support (M). Ra"and Hurturbise (F8)demonstrated that covolatilization of 1- and 2-naphthol with ethanol and water from fiiter paper previously treated with cyclodextrins can be prevented by treatment with NaCl or NaBr solutions. The retained naphthols can then be determined by roomtemperature phosphorescence at the subnanogram level. The same authors reported on changes in phosphorescence lifetime and other luminescence parameters as a function of temperature (F9).Changes are related to Young's modulus values and to a theoretical model that relates the changes bonding in cellulose. Also the same authors interactions of a single analyte adsorbed on two different type of matrices (fiiter paper and sodium acetate); the analyte used was p-aminobenzoate (FIO). The application of room-temperature phos horescence after paper electro horesis has been illustratef by Cheng and Vo-Dinh (FIIIpolyaromatic compounds electrophoretically separated were detected. Richmond and Hurtubise (FI2)have investigated the use of j3-cyclodextrin (j3-CD)INaClmixtures as solid supports in room-temperature fluorescence and phosphorescence measurements. Spectra obtained with a 30% P-CDINaCl mixture showed more fine structure than when fiter paper was used as a solid sup rt. According to the same authors (8'13)the luminescence cKacteristics of an analyte adsorbed on @-CD/NaCl are determined by the specific properties of this matrix and the ease with which the analyte can be accommodated by it. Considerations about the kinetics of luminescence for luminophon adsorbed on filter paper have been offered (F14). The paper discusses equations that relate radiative and nonradiative rate coefficients to preexponential factors and activation energy terms. Electrogenerated chemiluminescence has found use in analytical determinations (I);Vitt et al. have examined the effect of electrode material on such chemiluminescence of luminol (F15).The determination of N02(g) by luminol chemiluminescence has been evaluated by Kelly et al. (F16). Some amino alcohols (ethanolamine, diethanolamine, and triethanolamine) have been separated by ion-pair chromatography and then indirectly detected by their inhibition of the copper(I1) or cobalt(I1) enhancement of luminol chemiluminescence (FI7). Very sensitive determinations are possible by means of the chemiluminescence produced by reaction of Si, Ge, Al, and Cu atoms with F or volatile fluorine-containing compounds (e.g. SFGand NFJ in laser-generated plumes (F18).Picogram amounts of Si can be detected and the chemiluminescence signals are linearly correlated with amounts over two orders of magnitude. Amino-substituted polycyclic aromatic hydrocarbons have been determined in a continuous-flow system by usin photoinitiated chemiluminescence of peroxyoxalate (FI9f Imidazole was used to enhance the luminescence, and this permits detection of picrogram quantities of the analyte. Different aspecta of background chemiluminescence in peroxyoxalate chemiluminescenceused in chromatographic postcolumn detection have been discussed by Mann and Grayeski (F20).
OF ANALYTICAL CHEMISTRY
A method for estimation of the relative contribution of static and dynamic luminescence quenching has been pro osed by Carraway et al. (F21).The method is illustrated wit oxygen quenching of the luminescence of tris[ 1,lO-phenanthrolinelRu(I1) adsorbed on a silica surface. The quenching ability of water, oxygen, and air of the room-temperature fluorescence and phosphorescence of the protonated forms of benzomquinoline, benzo[h]quinoline, and a-naphthoflavone adsorbed on filter paper has been investigated (F22).Water was found to be the most efficient quencher, and fluorescence to be less sensitive to quenching than phosphorescence. The detection of particulate polycyclic aromatic hydrocarbons (e.g. in aerosols and in nondispersed NaCl particles coated with the hydrocarbons) by laser-induced time-resolved fluorescence has been described (F23).Table I1 compiles additional selected determinations based on chemi- and bioluminescence.
E
G. KINETIC METHODS BASED ON UNCATALYZED REACTIONS A kinetic approach with potentiometric monitoring for the determination of ascorbic acid, biotin, pyridoxine hydrochloride, and thiamine hydrochloride has been proposed (GI). The reaction of the analyte with N-bromosuccinimide was monitored, the rate of Br- production being followed with a bromideselective electrode. The approach was applied to the analysis of pharmaceutical preparations. Several papers have been published describing the use of continuous addition of reagent to a sample containing the analyte of interest. Thiamine at the nanomolar level has been determined by a reaction rate method using continuous addition of re ent ((32).The oxidation of analyte by hexacyanoferrate&) produces a product whose fluorescence was used to monitor the reaction. Initial-rate treatment of the rate information allows processing of 100 samples per hour with com etitive limits of detection and sensitivity. Continuous axdition of reagent has also been used to determine sulfonamides [ (3-30) X lo4 M range] the absorbance of azo dye produds being monitored (G3).The azo dye results from reacting the sulfonamide with 1-naphthol in acetate buffer (pH 4.15) and continuously adding nitrite ion as developing agent. Calibration curves were based on initial-rate measurements. Continuous addition of reagent has also been applied to the determination of zineb (a zinc-containing dithiocarbamate-type pesticide and fungicide) (G4). The method is based on the acidic decomposition of zineb and complexation of the liberated zinc with 2-carboxy-2'-hydroxy5'-(sulfoformazyl)benzene (zincon). The absorbance of the zinc complex with zincon was monitored at 620 nm. The determination is possible at microgram per milliliter levels and at a sample rate of 140 samples/h. The determination of zineb in vine and olive leaves was reported. A nonenzymatic reaction-rate alternative for the determination of urea in serum has been proposed (G5). It utilizes stopped-flow mixing and reaction with biacetyl in presence of thiosemicarbazide and iron(1II). Initial-rate measurements from absorbance-time data (530 nm) were used to prepare calibration curves. Fluorimetric monitoring of the quinogaline formed from dehydro-L-ascorbicacid and o-phenyle"ine has been used to determine L-ascorbicacid after its oxidation by mercury(I1) (G6).Initial rates were estimated with a fixed-time computational method. The approach, reported to have a limit of detection of 0.02 pg mL, was applied to the determination of ascorbic acid in m tivitamin pills and a fruit juice. On the basis of satisfactory recovery tests of added creatinine, Gutierrez et al. (G7) recommended determination of this analyte in serum and food products (dehydrated soup and meat extract) by an initial-rate method. Stopped-flow mixing and photometric monitoring at 500 nm were used to follow the reaction with picrate ion in basic medium. The kinetics of chemical and biolo 'caloxidation of sulfide in aqueous solutions has been r e p o J ( G 8 ) . The studies were conducted at 25 "C and with phosphate buffers of pH 8.0. The uncatalyzed chemical oxidation has only about 75 the rate of the biological oxidation at relatively low sul ide concentrations (
