Size exclusion chromatography - Analytical ... - ACS Publications

Anal. Chem. 1990, 62, 441 R-461 MM. PHARMACEUTICAL

(MI) Reffner, J. Pract. Spectr4sc. 1986, 6,179-96 (Eng). (MM2) Nichds k # c r o ~ C .Anel. 1989, (14), 29-31. NN. MICROCHEMICAL ANALYSIS (“1) (”2)

OellY, J. 0. Mlcrosc~pe1989,37 (2), 139-166. Wills, 8. W o s c o p e 1989, 37 (3/4), 255.

00. ORaANIC ANALYSIS (001) Liu. M. Zhongceoyao 1988. 79 (3), 129-31 (Ch). (002) Bryant, W. M. D. M/cfoscope1988. 36 (3/4), 183-190. (003) KeHner, R.; Kuhnert-Brandstaetter, M.; Hanns, M. Mikrochim. Acta 1988, 3 (M), 153-65 (Eng). PP. ASBESTOS ANALYSIS

(PPI) Millette, J. Microscope 1988, 36(1), 71-77. (PP2) McCrone. W. Microscope 1989. 37 (2), iii-iv. (PP3) McCrone. W. Microscope 1989. 37 (3/4). 403-409. (PP4) McCrone. W. Am. Envkon. Lab. 1989, (9), 60-65. (PP5) McCrone, W. Microscope 1989, 37 (I), 49-53. (PP6) Lott, P. F. Microchem. J. 1989, 39 (2), 145-8 (Eng). (PP7) Tech Bull. RS-blp-T-565, Cargiile Labs Inc.. 6 pp. (PP8) Shaffer, S. A.; Fox, M. J. Microscope 1989, 37 (3/4), 282. (PPg) Hamilton, M. NAC J. 1989, 7 (2), 44-46. (PPlO) Hamllton. M. Microscope 1989, 37, 3/4), 283. (PPI 1) Cooke, P. M. Microscope 1988,37 (3/4), 226-227.

R

(PP12) Colberg. M. NACJ. 1989, 7(1).17-19. (PP13) Mullkr, W. NAC. J . 1988, 6(1), 37-39. (PP14) Chatfleld, E. Microscope 1989, 37 (3/4). 283-284. (PP15) Miles, L.; Hopen, T.; Kuksuk. R. Microscope 1989, 37 (3/4). 274-275. (PPl6) MacDonald, H.; Bedore, J. €CON 1989. (8). 63-66. Mlcroscope 1989,37 (314). 284-285. (PP17) Lippert. E. Microscope 1988, 36 (3/4). 351. (PPl8) Armstrong, J. A.; Gray, J. C. Microscope 1989, 37 (314). 272. (PPIQ) Stewart, I . €fA-560/S-88-011 1988. (PP20) Perkins, R. Microscope 1989, 37 (3/4), 278-279. (PP21) Weber, J. S.; Janulls, R. J.; C a h r t . L. J.; C3Hespie, M. B. Mlcmscope 1989. 37 1314). 276-277. IPP22) k g h T:’F. Mi&mcope 1989. 37 (3/4). 377-387. Mefford. D. M i c r o s m 1989. 37 (3/4). 279-280. ,. --, Harvey, B. Micros& 1989, 37 (3/4); 393-402. (PP25) McCrone, W. Microscope 1989, 37 (3/4), 403-409. (PP28) Laughlin, G. J.; McCrone, W. Microscope 1989, 37 (I), 9-15. (PP27) hentice. J.; Keech, M. Microsc. Anal. 1989, (lo), 7-12. (PP28) Am. Lab. 1989,(11). 112. (PP29) Boltin, W. R.; Clark, 9. H.; Detter-Hoskin, L.; Kremer, T. Am. Lab. 1989. (4), 15-25. (PP30) Ainsiie, V. H.; Hays, S. M. Microscope 1989,37 (1). 77-88. (PP3l) Millette, J. R.; Burris. S. 9. Microscope 1988. 36 (314). 273-280. (PP32) Sahie, W.; Larsson, G. Ann. Occup. . Mg. . - 1989, 33 (l), 97-111 (Eng). (PP33) Landgraf, K. F. Pharmarle 1988, 43 (I), 20-3 (Ger).

.

Kinetic Determinations and Some Kinetic Aspects of Analytical Chemistry Horacio A. Mottola Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078-0447

Dolores P6rez-Bendito Department of Analytical Chemistry, University of Cbrdoba, 14071 Cbrdoba, Spain

Harry B. Mark, Jr.* Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221

This review retains, basicall ,the organizational structure The papers reviewed have of previous ones in this series been selected from those that appeared since November 1987 and were available for the authors’ consideration through approximately November 1989. Attention to the general theme of this review series by the community of analytical chemists continues the trend advanced in the previous review. The Third International Symposium on Kinetics in Analytical Chemistry took place in Cavtat (by Dubrovnik), Yugoslavia, from September 25 to September 28,1989. A special issue of The Analyst (London) will be dedicated to the plenary, invited, and contributed presentations at this meeting, which blended scientific communication with the peaceful beauty of the Adriatic sea and the medieval enchantment of the surroundings. The Fourth International Symposium on Kinetics in Analytical Chemistry is scheduled to take place in 1992 at the Institute of Physical and Theoretical Chemistry, University of Erlangen-Nuremberg, in West Germany. Among the more than 4500 papers presented at the 1989 International Chemical Congress of Pacific Basin Societies (Honolulu, HI, December 17 to December 22,1989), 27 made up a symposium on Kinetics Aspects in Analytical Chemistry. Analytica Chimica Acta dedicated a special issue (Vol. 224,

6).

0003-2700/90/0362-441R$09.5Ol0

No. 2) to kinetics in analytical chemistry. Stanley R. Crouch (Michigan State University), who arranged this special issue, grouped the papers in four thematic sections: (1) kinetic studies, (2) instrumentation, (3) new measurements and data analysis techniques, and (4)kinetic determinations.

BOOKS AND REVIEWS A new monograph dedicated to kinetic methods of determination has been published (2);of particular interest in this monograph is Chapter 9 on the “analysis of real samples”. A very concise review of kinetic methods for trace analysis in biological samples has been prepared (3). The overview is organized around catalytic determinations (homogeneous and heterogeneous systems), methods using uncatalyzed reactions, and implementations in flow injection analysis. Kinetic determinations based on uncatalyzed reactions were reviewed (4) according to reaction type, primarily complexation reactions. Catalytic methods were discussed in Ja anese by Nakano and Kawashima (5) with focus on spectropIotometric monitoring. The kinetics of anodic dissolution of metals, a fundamental aspect of analytical techniques such as anodic stripping, has received a thorough discussion (6). 0 1990 American Chemical Society

441 R

KINETIC ASPECTS

OF

ANALYTICAL CHEMISTRY

naaclo A. Mmda. Professor 01 Chemishy. Oklahoma State University. was born in Buenos Aims. Argentina. and remived his undergraduate and graduate education at the University 01 BUBIIOS Aires. He earned Licenclate and Doctoral degrees from the University of Buenos Aims and dd predoctral Work with Professor Erne51 8. Sandell at the University of Minnesota (Minneapolis). He $Dent 2 vears a1 the UniversBv of Ariz-

-

sociate in Proles~orHenry Freirer'r re-~ Search group. After teaching for 2 yews at ,' the Universitv of the Pacific IStockton. CA). he joined OSU in the fall 01'1967. His &search 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 conllnuous-flow systems. chemically modified electrodes tor sensing in flow systems. analytical separations. and photochromism of metal chelates. He is the author of a recent monograph on "Kinetic Aspects of Analytical Chemisny".

Dolorea P6rez-BendHo is currently RolesSOT of Analytical Chemistry at the University 01 Ckdoba. Soain. She earned the h . 0 . degree in 1968 from the University 01 Seville. Spain. After 7 years as Assistant P~D1es.s~at the University 01 Seville. she pined the FacuRy 01 Sciences at the University 01 C6rdoba and since 1980 she has been a professor in the Department of Analytical Chemistry of this institution. Professor P6rez-BendiiO's reseerch interests include trace analysis. molecular spectroscopy. and kinetic methods of determination With e m phasis on differential rate methods and catalytic determinations with photometric and lluorometric 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".

I'

Harry 8. Mark. Jr.. Professor 01 Chemism. University 01 Cincinnati. received his B.A. degree from the University of Virginia in 1956 and his Ph.D. degree from Duke University in 1960. He was a postdoctoral research ~ssociateat the University 01 NaRh Carolina With C. N. Reillev) from 1960 to 1962 andat the California insliiute Of Technology [with F. C. Anson) from 1962 I O 1963. He was a member 01 the stall of the Depanment 01 Chemistry at the University of Michisan from 1963 to 1970, Visiting Prfessor of Chemistw at the Universite Libre de ~ r u x e ~ ~ a e1970. s . and pined the staff at the University of Cincinnati in 1970. He was L % lhe Dmanment Head from 1976 lo 1961. His research interests are in elec. trachemistry, surface Chemistry. kinetic methods of analysis. environmental analytical problems. and instrumentation. I n addition to research papers. he is the coauthor of the books "Kinetics in Analytical Chemistry". "Activated Carbon: Surface Chemistry and Adsorption from Solution". and "Simplified Circuit Analysis: Digital-Analog Logic". He is also a coeditor of the monograph series "Computers in Chemism and Instrumentation" and "Water Qually Handbook" and has been a member of the editorial board of AnaWical Chemisfv.AnsIy7ical Lepers. Chemical InsWmnlaflon. and Tabota.

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A c r i t i c a l evaluation of k i n e t i c asperts in t h e r m a l analysis has been presented (71. T h e a u t h o r s p o i n t t o t h e danger of rearhing meaningless conclusions w h e n oversimplified k i n e t i c e q u a t i m s a r e u s d a n d p h y s i c a l a n d c h r m i r a l sutiprocesses a r e ignored. K i n e t i c approaches t o d e t e r m i n a t i o n u s i n g flow i n j e c t i o n procedures have been reviewed (8). Fixed-time, variable-time, and initial-rate imnlementations and auolications in o w n and in closed-loop conhgurations are c o v e k d . A f e w appfications of f i x e d - t i m e determinations u s i n g stopped-flow mixing have been discussed (9)a n d some recently p u b l i s h e d applications of rate-based determinations u s i n g stopped-flow m i x i n g have also b e e n reviewed (IO). T h i s concise p a p e r focuses o n t h e w o r k carried o u t in t h e authors' l a b o r a t o r y (e.g., c o n s t r u c t i o n of a m o d u l a r stopped-flow unit a n d i t s use with d i o d e a r r a y and chemiluminescence detection), mentions applications with 442R

ANALYTICAL CHEMISTRY, VOL. 62, NO. 12, JUNE 15. 1990

clinical, pharmaceutical, food, agricultural, and environmental samples, briefly discusses an a l t e r n a t i v e t o t h e stopped-flow technique (continuous a d d i t i o n of reagent a t a constant rate), and presents t h e authors' views o n c o m i n g trends. A t i m e l y r e v i e w on c h e m i c a l l y m o d i f i e d electrodes h a s appeared (11). T h i s well-organized overview can be considered as a m i n i m o n o g r a p h on t h e topic, w h i c h is i n t i m a t e l y r e l a t e d to electrocatalysis. T h e r a t e of e l e c t r o n transfer a t glassy c a r b o n surfaces c a n b e e n h a n c e d by d i f f e r e n t p o l i s h i n g m e t h o d s a n d by h e a t or electrochemical t r e a t m e n t . These surface preparations have been described (12). P r i n c i p l e s and a p p l i c a t i o n s of time-resolved fluorescence i m m u n o a s s a y s h a v e been r e v i e w e d (13) a n d t h e same t o p i c overviewed (14). B i o l u m i n e s c e n t a p p l i c a t i o n s ( c l i n i c a l a n d b i o c h e m i c a l ) of luciferase and l u c i f e r i n were reviewed (15). A selective and b r i e f d e s c r i p t i o n of r e c e n t c o n t r i b u t i o n s to analytical chemiluminescence has been presented (16). Recent a n a l y t i c a l developments in solid-surface luminescence spect r o m e t r y h a v e b e e n discussed K i n e t i c determinations u s i n g fluorescence m o n i t o r i n g h a v e been reviewed, in Hungarian, by K a s a (18). "Stat M e t h o d s " for catalyzed a n d u n c a t a l y z e d reactions employing electrochemical sensors (e.g., pH-stat, potentiustat, ampernstat, a n d bioamperustat) and spectrophotometric and luminescence m o n i t o r s (e.g., ahsorptiostat, fluorostat, a n d l u m i n o s t a t ) w e r e r e v i e w e d (19). T h e a n a l y t i c a l p o t e n t i a l o f oscillating reactions has been examined (20);basic i n f o r m a t i o n a b o u t t h i s class of chemical p h e n o m e n o n is outlined. P a n t e l and W e i s z (21) r e v i e w e d c a t a l y t i c e n d - p o i n t d e t e c t i o n in t i trimetric determinations. T h e use of F o u r i e r - t r a n s f o r m i n f r a r e d reflectance spect r o m e t r y for t h e monitoring of r e a c t i o n r a t e s h a s been discussed (22). T h e r e v i e w covers a t t e n u a t e d total reflectance, e x t e r n a l reflection, a n d d i f f u s e reflectance spectroscopy. Time-resolved, relaxation, o r steady-state applications are n o t included.

(In.

A. KINETIC MErnoDs FOR DETERMINATION OF CATALYSTS T h e growth of t h e n u m b e r of a p p l i c a t i o n s to r e a l a n d s y n t h e t i c samples a n d t h e use of a u t o m a t i c techniques. p a r t i c u l a r l y flow i n j e c t i o n analysis, r e p o r t e d in t h e past review were also a t r e n d in t h e p e r i o d reviewed here. T n h l e I s u m marizes t h e most relevant features of t h e m e t h o d s for d i r e c t d e t e r m i n a t i o n of r a t a l v s u r r p n r t e d in t h e lnst 2 year.;. 1)ezpite t h e r e l a t i v e l y extensive use 111a u t w a t a l y t i r r e a r tions, t h e r e is a l a r k uf i n f o r m a t i o n a h o u t h o w t h e r a t e con. stants o f s u r h reartions ran he determined f r o m experimental dam. In t h i s respert. a n arcurate m e t h d f o r t h e obtainment of a u t o c a t a l y t i c r e a r t i o n rates was r e p o r t e d recently iAA:ii. It was applied lo t h e autocatal.vlic oxidation of dimethylamine h y p e r m o n g s n n t r i o n s in nn aqueous Solution. %me g e n r r a l i z n t i u n s a n d exnmples i l l u s t r a t i n g thc. changes in t h r inl l e c t i o n t i m e (;.e., the t i m e at the i n f l t c t i m point uf the kinetic r u r v e ) w i t h t h e i n i t i a l c o n c e n t r n t i i m s uf t h e i n r r t d i e n t s d a u t o c a t a l y t i c reactions of different r a t e laws ha;e also been r~. e= n o-r t ~ e d- (AR4). .~~ - ~~. ~ Trace amounts of a d v e n t i t i u u transition metals in hiiffered solutiuns c n n a r t as r a t n l y s t s f o r a n i i m h e r of o x i d a t i o n pro. cesses. T o full!. u n d r r i t a n d t h e r o l e t h a t these m e t a l s m a y play, t h e b u f f e r solution must be free from t h e catalytic metal. A s r o r b a t e ion has heen proposed for d e t e r m i n i n g c a t a l y t i r m e t a l s in t h i s t y p e of s o l u t i o n (A851,where i t is stable even a t ptl 7 a n d is a e r i a l l y o x i d i z e d i?a f i r s t - o r d e r r e a r t i o n w i t h a r a t e c o n s t n n t less t h a n 6 X 10- s-'; t h e calibration graphs f o r t h e aerial o x i d a t i n n of avcorhate are linear in t h e p r e w n c e of Cu a n d F e traces. A l t h o u g h t h e e n h a n c i n g effect of m i c e l l a r m e d i a on t h e reaction rate is c u r r e n t l y heing t h e suhject of extensive study. i t is r a t h e r s u r p r i s i n g t h a t s u r h m e d i a have n o t so far been used in r u n v e n t i o n a l k i n e t i r determinations. d e s p i t e t h e ahundant literature showing t h a t appropriate mirelles r a n c a t a l y r e c h e m i c a l reactions a n d have a great p o t r n t i a l in k i n e t i c analysis tA86'1. T h e role of micellar media in analytical r e a r t i o n r a t e m e t h o d s was r e r e n t l y discussed ( A K J on t h e hasis of t h e i i n r a t a l p e d a n d indiderataly7ed reactiun hetween Cr(lV1 a n d As{1111 in t h e presence o f d o d e c y l t r i m e t h y l . a m m o n i u m b r o m i d e ~DI'ARI,w h i r h was fvund t u increase

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

antimony phosphate + heptamolybdate + ascorbic acid cadmium Co(II1) + a,&y,&tetrakis(4-sulfophenyl)porphine

0-1 x 106

cobalt

0.01

Nfi-diethylphenylenediaminesulfate +

HzOz

protocatechuic acid

+

0.5-16

0.005

HzOz tiron + HzOl hydrazine + HzOz catechol

3-120 2-1500

+ HzOz

permanganate decomposition quinalizarin + Hz02 Bromophenol Red

+

HZ02

copper

thiosulfate + Fe(II1)

hydroquinone

metol

2000-8000 0-50 0.2 0-400

+ HzOz

+ H202

permanganate decomposition hydroxylamine + HzOz

3000-12000

3-hydroxy-2-naphthoic acid + HzOz hydroquinone + HzOz

0.06-1.0

salicylic acid

+ H202

5-500

0-50 200-2oooo

iron(II1) + thiosulfate

0-180

indium

diphenylamine + KI04

0.6-16 0.03-1.5

iodine

4-amino-4’-methoxydiphenylamine + KI03 Ce(1V) + As(II1)

Ce(1V) + As(II1)

3.8-500

Ce(1V) + As(II1)

2-100

Ce(1V) + As(II1)

0-4000

Ce(1V) + As(II1) Fe(II1) + SCN-NOZ- + SCN

2-20

comment8 enhancing effect of antimony on the Molybdenum Blue reaction; flow injection method with photometric detection; 120 samples/h photometric (432 nm) and fluorimetric monitoring (fluorescence intensity at 644 nm) in the presence of imidazole, which also acta as a catalyst; fixed-time method photometric monitoring

type of sample

ref A1

wastewater

A2

A3

photometric monitoring; continuous-flow system with water (sea and river) in-line preconcentration and separation of cobalt from interferenta thermometric monitoring; only Ni and Mn interfere vitamin BIZin a collyrium thermometric monitoring; interfered by Mn and P b catalyst supported on y-alumina photometric monitoring; fixed-time method (15 min) urine, with mineralization of the sample thermometric monitoring; interfered by Ni, Ag, Pb, and Fe photometric monitoring; flow injection system; 120 samples/ h photometric monitoring; ammoniacal medium at 100 OC high-purity materials

A4

photometric monitoring of the absorbance decrease at 525 nm of the Fe(S20&- complex to yield Fe(I1) and S40& based on the use of a large excess of iron with respect to thiosulfate; fixed-time method (t = 0.5 min) photometric monitoring in the presence of an ammonia-fluoride buffer which acta as an activator; 3-fold excesses or iron are tolerated; uses the tangent method photometric monitoring; recoveries higher than 95% from water samples thermometric monitoring; interfered by Ni, Ag, Pb and Fe thermometric monitoring; RSD = 2.3%; interfered by Fe, Co, and Ni photometric monitoring; sensitive and selective method, only interfered by Fe(II1); a mechanism is proposed Photometric monitoring; flow injection analysis; recoveries between 92 and 104%; 24 samples/h photometric monitoring; the copper(I1) ion bound to the protein is not an effective catalyst for the system; good selectivity photometric monitoring at 525 nm; flow injection system; 40 samples/h; rather selective method; special problems encountered in designing an FIA manifold to implement a catalytic reaction are discussed photometric monitoring at 582 nm; interfered by a 20-fold excess of Au photometric monitoring at 540 nm; interfered by a 5000-fold excess of c u photometric monitoring; various digestion procedures and modifications to the sample pretreatment were assayed; samples were dry digested in a nickel crucible in the presence of KCl to reduce iodine adsorption fluorimetric monitoring; flow injection analysis; iodide and thiocyanate are separated from lysozyme by gel filtration chromatography; the method also allows thiocyanate to be determined uses a modular photometric stopped-flow system specially suited to routine analyses; the features of the proposed stopped-flow method are compared with those of ita conventional kinetic counterpart; good selectivity photometric monitoring at 446 nm of the red complex formed in the presence of brucine, which acta as an inhibitor of the redox reaction and as a color-forming reagent photometric monitoring in the presence of brucine; RSD = 3.8% (n = 6); recoveries of 95% for 45-440 ppb I in water photometric monitoring at 533 nm; overall relative error of 14.3%

metals, steels, and alloys and biological samples pepper bush, bovine liver, human urine) human and mouse muscle

All

river water and cabbage

A13

A5 A6

AI A8 A9 A10

A12

A8 plasma

A14

atmospheric aerosol samples A15 natural waters

A16

human blood serum

A17 A18

A26 A26 biological materials (alfalfa A19 meal, sheep and cow milk, sheep whole blood) and tap water A20

pharmaceuticals, table salt, and milk samples

A21

rain water

A22

sea water

A23

commercial acetic acid

A24

ANALYTICAL CHEMISTRY, VOL. 62, NO. 12, JUNE 15, 1990

443R

KINETIC ASPECTS OF ANALYTICAL CHEMISTRY ~

Table I (Continued)

species

indicator reaction Fe(II1)-SCN-

iron

+ NO,

rosaniline + aerial photochemical oxidation o-aminophenol + photolytic product bf antiraqiinone Tl(II1) + HzOz

dynamic range or detection limit, ng/mL 100

100-1oO0

comments

type of sample

photometric monitoring of the decomposition of the geochemical samples ferric thiocyanate complex by nitrite in an HN03 medium; the potential interference of over 40 ions was investigated photometric monitoring of the decrease in the dye chemicals of analytical absorbance upon irradiation with light of a reagent grade wavelength shorter than 360 nm RSD of 3.8% for a sample containing 0.5 pg/mL soil samples

0.1-1.4 (20 "C); the reaction is induced by Fe(I1); potentiometric 0.2-2.8 (15 "C) monitoring with a Tl(1)-selective electrode; a number of metals and nonmetal species are tolerated in 100-fold amounts and over 1.25-13 catalyzed by the Fe(II1)-triethylenetetraamine H202decomposition complex; thermometric monitoring; the reaction is catalyzed by a number of metal ions, none of which interferes in applying the method to petroleum products; only Mn(I1) poses as serious interference photometric monitoring of the absorbance decrease Arsenazo I + H202 1-4 at 500 nm; 2,2'-bipyridyl is used as an activator photometric monitoring at 514 nm; fixed-time N,N-dimethyl-p0-2.4 method (t = 5 min); highly selective and precise; phenylenediamine + the reaction is catalyzed by Fe(I1) and Fe(II1) HzOz chromotropic acid + photometric monitoring; optimization of the system for the determination of Fe(II1) through the H202 experimental design used; a virtually satisfactory statistical model is derived Indigo Carmine + Hz02 1-100 Photometric monitoring of the absorbance decrease at 540-640 nm; the reaction is catalyzed by Fe(I1) at pH 4.0 in the presence of tartaric acid as an inhibitor of the uncatalyzed reaction photometric monitoring; 1,lO-phenanthrolineis Sulfanilic acid + KIO, 11-55.8 used as activator; highly precise and selective fixed-time method ( t = 10 min) photometric monitoring at 400 nm; rather selective lead 4-(3,4-dihydroxyphenyl- 5-100 azo)benzenesulfonic method; coef of variation 5 6 % acid K2S208 manganese Pyrogallol Red + H202 0-32 photometric monitoring of the absorbance decrease at 540 nm; 2,2'-dipyridyl is used as an activator photochemical 0.5-131 the system is sensitized by riboflavin; the reaction oxidation of rate is increased by catalase and decreased by o-dianisidine superoxide dismutase o-dianisidine + Hz02 0.2-1.0 photometric monitoring at 440 nm; phenanthroline and tiron are used as activators; the effect of foreign ions is examined Malachite Green + 0.2-7 combination of ion-exchange separation and flow injection method; sample volume, 100 pL KIO, Malachite Green + 0.4-5.0 nitrilotriacetic acid is used as an activator; KIO, photometric monitoring at 615 nm; variable-time method; the interfering effect of Fe and Co and other metal ions is discussed Malachite Green + samples are acidified with HNO, and reacted with KIO, the indicator system at pH 3.8 for catalytic decolorization photometric monitoring at 615 nm in a flow Malachite Green + 0-2 KIO, injection system; pH 4.4, T = 50 k 1 "C; injected sample volume, 20 pL; reaction coil length, 2 m Malachite Green + 0.4-1.0 photometric monitoring at dl5 nm; nitrilotriacetic KIO, acid is used as an activator Malachite Green + a procedure for treatment of bronze samples is KIO, reported; fixed-time method (5 min) based on absorbance measurements at 620 nm; manganese recoveries ranging from 97 to 106% Malachite Green + 0.02 the reaction is carried out in the presence of KIO, nitrilotriacetic acid as activator and NaF as masking agent; large amounts of a number of metal ions pose no interference 3-(2-hydroxyphenylazo)- 0.5-9.1 photometric monitoring at 472 nm; initial-rate pyridine-2,6-diol + method; the most serious interferents are Sn(I1) and EDTA, while most anions cause no H2Oz interference N,"-diethylaniline + 0.02-1.0 photometric monitoring at 475 nm by the normal KIO, and stopped-flow injection modes; 40 and 25 samples/h, respectively

+

444R ANALYTICAL CHEMISTRY, VOL. 62, NO. 12, JUNE 15, 1990

ref A25

A27 A28

standard zinc and spring water

A29

petroleum products

A30

Dy, Gd, and Er oxides

A31

natural waters

A32 A33

river water, tartaric acid, and Ni alloy

A34

A35 NaCl and Pb-doped mercury A36 telluride semiconductor films well water A31 A38 A39 chemicals (HF, "OB, HCl, and Si and Ti samples) spring water

A40

mineral, spring, and tap water

A42

A41

A43 sea water

A44

ancient bronze ware

A45

waters (tap and spring)

A46

foodstuffs (coffee, rice, beer, and tap water)

A47

A48


Table I (Continued)

species

indicator reaction N,”-diethylaniline KIO,

+

decomposition of HzOz

HzPO2- + KI04

Bromophenol Blue KIOI

+

Eriochrome Blue Black R + HzOz in a basic medium aerial oxidation of Morin mercury

hexacyanoferrate(I1) t 2,2’-bipyridyl hexacyanoferrate(I1) + isonicotinoyl hydrazide a,@,y,b-tetrakis(4-sulfophenylporphine) + Co(I1) photoxidation of EDTA by iodine

molybdenum I-

+ HZOZ

I-

+ HzOz

I-

- B r 0 9 + ascorbic acid

nickel

decomposition of permanganate

osmium

Ce(1V) + As(II1)

o-naphtholphthalein + KIO, aerial oxidation of N-(l-methoxyphenyl)p-phenylenediamine 4-methylaminophenol + HzOz ruthenium

Methyl Orange + NaIO,

decomposition of the Co(III)-5,10,15,20-tetrakis(4-sulfonatopheny1)porphine complex by B r 0 9

dynamic range or detection limit, ng/mL

comments

stopped-flow injection method with photometric detection; RSD of 0.19 and 0.05 for a Mn concentration of 0.1 and 0.4 ng/mL, respectively thermometric monitoring; the influence of various 0.1-13 ligands [hydrazine, Tiron, triethylenetetraamine (TETA)] on the decomposition of HzOZwas studied; the Mn(I1)-TETA complex was chosen for the determination of Mn; only Fe(II1) interferes at low concentration levels stopped-flow reversed flow injection system; 0-5 nitrilotriacetic acid is used as an activator; most foreign ions do not interfere, but Co(I1) concentrations above 4 ng/mL cause a negative interference photometric monitoring at 578 nm; 0.640 1,lO-phenanthroline is used; pH between 3.0 and 4.6 photometric monitoring; the interfering effect of 27 0-1.6 species is reported; the species interfering at the lowest concentrations are Fe, Ni, and Zn (0.2, 0.4, and 0.5 ng/mL, respectively) fluorimetric monitoring; the method was also applied in the presence of Zr(1V) as activator; real samples were digested with HN03 in pressurized Teflon reactors 2 photometric monitoring; the color-forming reaction is enhanced by adding thiourea; coef of variation, 3.72 (n = 11); recoveries in the range 96-106% photometric monitoring of a ligand exchange 120-480 reaction; RSD = 0.74%; the effect of foreign ions is examined fluorimetric monitoring at 644 nm of the 0.4-8.0; fluorescence intensity of the direct formation of 12.0-24.0 the Co(I1) complex; fixed-time method; RSD = 6.9% and recoveries ranging between 93 and 105% amperometric monitoring by measuring the time 0.4+ 4-42 required for cancellation of the reduction current of iodine; two calibration graphs are used depending on the experimental conditions potentiometric monitoring of the iodide 0-320 concentration with an iodide-selective electrode; the potential can be monitored automatically; interfered by some metal ions; Fe and Cu are masked with EDTA 1-40 photometric monitoring; use of a flow injection manifold with ion-exchange separation to remove interferents, which are eluted to waste; RSD hexacyanoferrate(I1) + o-phenanthroline

silver

oxidation of reduced phenolphthalein by persulfate in the presence of a'-bipyridine oxidation of reduced phenolphthalein by ammonium persulfate in the presence of ethylenediamine Mn(I1) + (NH4)2S208

uranium

0.7-41.0; 0.1-2.5 (after preoxidation to Ru(VII1) Flow-injection spectrophotometric method; 2500-25000 EDTA is used as a general masking agent; NazBaY complex is added to the alkaline sulfide to inhibit the photochemical reaction between the dye and EDTA photometric monitoring of the system in the 2 presence of the Griess reagent, which reacts with the nitrite yielded photometric monitoring of the Fe(phen),2+ complex formed; the apparent activation energy of the catalyzed and uncatalyzed reaction is 64.15 and 96.89 kJ/mol, respectively; RS = 2.43% photometric monitoring at 550 nm of the red 0-115 product formed

0-60

30-150

decomposition of H20z in an alkaline medium

810-6400

vanadium chromotropic acid KBr03

+

1.2-1 30

chromotropic acid KBr03

+

5-80

0.4-200 (4-(4-diethylamino)-2hydroxyphenylazol-5hydroxynaph&alene-2,7disulfonic acid (Beryllon) + ascorbic acid Catechol violet + KBr03 0-4.8 0.05-2.0

0.032

ref A68

K4[Ru(CN)6].3H20complex A69 ores and pharmaceutical preparations

A70

wastewater

A7 1

geological samples

A72

drinking and waste waters

A73

photometric monitoring at 550 nm of the red product formed

environmental waters

A74

photometric monitoring at 540 nm of the permanganate formed in a phosphoric medium; tolerances to 30 ions are reported photometric monitoring of the ligand-exchange reaction; RSD = 0.69%; the effect of foreign ions was examined stopped-flow spectrophotometric method; the conditional reaction rate constant was calculated; selective method, 50-1000-fold excesses of NH4+,Ca, Al, Fe, Mo, PO4", S04z-, and F cause no interference thermometric monitoring of the system in an acid medium; RSD of 2.2% for 50 ppb of V; various ions do not interfere in 500-fold excesses photometric monitoring at 430 nm; pH 3.8, T = 30 OC; after 10 min, the reaction is stopped by adding NazCz04 photometric monitoring at 475 nm of the absorbance decrease of beryllon; the catalytic action can be stopped at any time by adding EDTA; a procedure for pretreatment of rocks and minerals is reported

LiC03

A75

rocks and minerals

A79

photometric monitoring with a,a'-bipyridyl as activator; a mechanism for the decolorization reaction is proposed flow-injection spectrophotometric method; Tiron is used as activator; V(1V) and V(V) can be determined at a rate of 30 samples/h

human hair and food

A80

natural waters

A81

waters

A82

photometric monitoring at 530 nm of the dye decolorization; the reaction is stopped after 3 min by rapid cooling; tolerances to 27 ions are reported

the reaction rate of both systems. The results of this study show the advantages of usin DTAB micellar systems in the determination of Ce(IV)-t!e substrate-in terms of sensitivity, selectivity, and detection limit and of iodide-the catalyst-with increased selectivity. Koupparis et al. studied and applied the catalyzed reactions of l-fluoro-2,4-dinitrobenzene (FDNB) with amino (A88) and phenol compounds (A891 by using a fluoride-selective electrode for the potentiometric monitoring of the halide released in the organic reactions involved. The two systems are catalyzed by cetylmethylammonium bromide (CTAB), the effect of which on 13 amino acids was studied and correlated with the structure of the amino acid. Cephalexin, 2-amino-2-thiazole, 446R

Ni slimes and Pt-group metal ore concentrates

photometric monitoring; the reaction is carried out in a 0.08 M HCl medium; the effect of various transition metal ions was studied thermometric monitoring; sulfuric medium

hexacyanoferrate(I1) + isonicotinoylhydrazide

oxidative coupling of NJV-dimethylaniline and 4-aminoantipyrine by BrOr Eriochrome Blue Black R + KBr03

type of sample

comments


A56 phosphoric acid and phosphate ores

A76

petroleum products

A77 A78

sulfamethiazole, dopamine, and 2-thiobarbituric acid can be determined at concentrations between lo-' and lo6 M by the initial-rate or the fixed-time method. CTAB itself and other surfactants can also be determined on the basis of their catalytic effect on the slow reaction between phenylalanine and FDNB. This kinetic catalytic method offers satisfactory performance in the determination of cephalexin, sulfamethiazole, and CTAB in pharmaceutical formulations (A88). Micellar catalysis was found to enhance the rate of reaction of various phenol compounds assayed by factors between 37 and 290. Phenol, acetamino hen, isoxsuprine, nylidrin, isoproterenol, and metaramino were determined kinetically at concentrations in the range 7 X 10% X lo4 M; acetamino-

P


phen was also assayed in commercial formulations (A89). A new indicator reaction for the catalytic determination of iodine based on the oxidation of As(II1) by hexacyanoferrate(II1) in a ueous sulfuric acid was reported by Sriraman ey studied the catalyzed reaction and put et al. ( A M ) . forward a mechanism for the steady-state and preequilibrium processes involved, which they contrasted with the well-known mechanism of the classic Ce(1V)-As(II1) reaction. This new reaction allows the determination of iodine and iodide at concentrations between 12 and 60 ng/mL by monitoring the absorbance of unreacted hexacyanoferrate(II1)at 415 nm. The system offers definite advantages over the Ce(1V)-As(II1) reaction. The oxidation of N-methyldiphenylamine-4-sulfonic acid in weakly acidic solutions has been exploited for the catalytic spectro hotometric determination of metals of the Pt family such as% and Ru (A91)in a study that included the oxidation of organic compounds by various agents (e.g., iodate) in sulfuric acid. The ubiquitous Ce(1V)-As(II1) system was recently used for the first time for the kinetic determination of Cr(III), a catalyst for this reaction (A92). The optimum ex erimental conditions r uired are typical of a pseudo-fit-or er process, with the A S ~ I concentration ) in excess over that of Ce(1V) at a fixed concentration (0.1 M) of sulfuric acid. The absorbance of the system is monitored at 430 nm and application of the fixed-time method allows the determination of Cr(II1) in the range 10-40 pg/mL. The determination is only interfered by Ag and Mn, while relatively large excesses of Fe, Cu, and Zr are tolerated. The determination of the substrate of a catalytic reaction has been addressed by several authors. Thus, hydrogen eroxide has been determined by a flow in’ection method Eased on its reaction with Stilbazo, catalyzed Ly Co(I1) (A93). A 90 pM solution of Stilbazo containing 0.5 pg mL Co(I1) and a buffer of pH 11.9 were each fed into the IA system at a flow rate of 1.0 mL/min. The resulting mixture was then mer ed with a water stream flowing at a rate of 2.0 mL/min whi$ acted as a Sam le carrier into which the H202solution (390 pL) was injecteland driven to a 3.5-mm reaction tube thermostated at 30 OC. By measuring the absorbance decrease at 503 nm, hydro en peroxide can be determined in the range 0.1-10 pg/mL. i n ion-exchange column was placed immediately after the sample injection port to remove potentially interfering heavy metals. A sampling rate of 30 and 75 samples/h was achieved with and without the ion-exchange column, respectively. The ferric complex of triethylamine (TETA-Fe3+),which is known to emulate the activity of the enzyme catalase, replaced peroxidase in a sensitive nonenzymatic method for the determination of hydrogen peroxide and organic hydroperoxides (tert-butyl and linoleic hydroperoxide) in the presence of the TETA chelate by wing homavanillic acid as a hydrogen donor (A94). By the catalytic action of the complex, homovanillic acid is oxidized to its fluorescent dimer, the rate of change of the fluorescence being recorded at 425 nm (Aex = 315 nm). By using the initial-rate method, Hz02can be determined a t concentrations as low as 0.034 pg/mL and the organic hydroperoxides in the range 0.312-0.0312 mg/mL. The method is equally applicable to the determination of substrateenzyme systems yielding H202,viz., glucosqlucose oxidase, which allows the carbohydrate to be determined at concentrations below 10 pg/mL. The method was applied to the determination of hydrogen peroxide and glucose in plasma. A novel spectrophotometric method for the determination of eroxydisulfate ion using the o-dianisidine-peroxydis d t e - c o per(I1) indicator reaction (A%) involves monitoring the absoriance at 450 nm at 30- or 60-s intervals for 8 min. The response is linear between 1.6 pM and 0.1 mM S20z- and the method is interfered by nitrate ion. A few kinetic methods for the determination of inorganic anionic catalysts have been described. Thus, bromide can be determined spectrophotometrically over the concentration ran e 1 13 pg/mL on the basis of its catalytic effect on the 1-3’-azo)-1-naphthol by oxifation of 4-(l’-H-l’,2’,4’-triazol bromate in an acid medium (AMY. The reaction rate is monitored by measuring the absorbance decrease a t 415 nm and applying the initial-rate method. By using the same system but peroxydisulfate instead of bromate, As(II1) can be determined in the concentration range 1.6-12.9 pg/mL-it

TI

B

4

is another catalyst for the oxidation of azo compounds-by monitoring the absorbance at 490 nm. The selectivity of both methods is somewhat poor. The Pyrocatechol Violet-hydrogen peroxide system has been used in the kinetic spectrophotometric determination of bromide ion, which exerts a catalytic effect on the reaction, by using a conventional and a flow injection manifold. By wing the conventional kinetic a proach (A97),bromide can be determined at concentrations &tween 0.004 and 0.3 pg/mL in a HCl/H#04 medium by monitoring the absorbance at 550 nm and applying the fixed-time method (t = 2 min). The effect of bromide ion is considerably enhanced by chloride ion, the activating effect of which was taken into account by the proponents of the method in uttin forward a mechanisms for the reactions involved. TEe metiod is not interfered by most ions commonly occurring in natural waters, except iodide, and was applied to the determination of bromide in river and pond waters. Its FIA counterpart was found to be less sensitive (A98). The calibration graph was linear over the range 0.01-0.6 pg/mL and the sampling rate was 45 samples h for an in’ected volume of 500 pL. The method was also appiied to the determination of bromide ion in river, lake, hot spring, and sea water, with satisfactory results in every case. Piezoelectric quartz crystals were not used in kinetic analyses until very recently. In fact, one such crystal was used as a detector for iodine in its bromide-catalyzed oxidation to iodate by permanganate in a sulfuric medium (A99). After the iodine is extracted into toluene, the resulting frequency change caused by iodine adsorption on the crystal electrode varies linearly with the bromide concentration over the range (0.5-5) X 10-l2M according to the equation

[Br-] = f11.2 - (Af/Zl.5)] x 10-l2 M where A i is expressed in hertz. Chloride ion also appears to exert a catalytic effect on the reaction, but the frequency change is about 300-400 times smaller than that caused by bromide at the same concentration. The method was applied to the determination of bromide ion in water samples. The catalytic action of nitrite on the oxidation of pyridine-%aldehyde 2-pyridylhydrazone in an acid medium was exploited for the determination of the anion in water (AI&?). The reaction was monitored spectrophotometrically at 372 nm and the method allows the determination of nitrite in the concentration range 0.04-4 pg/mL with an RSD of 1.5%. While large amounts of nitrate and ammonium ions do not interfere with the method, Cu, Pb, and electroactive species cause disturbing effects. Another catalytic method for the determination of nitrite reported in the reviewed period is based on the oxidation of Fe(I1) by dissolved oxygen in its presence (AIOI). The catalytic reaction is stopped by adding urea and the Fe(II1) yielded is measured by the thiocyanate method. The calibration ra h run is linear in the range 0.02-0.5 pg/mL. The metiofwas applied to the determination of nitrite in foods and waters with satisfactory results in all cases. The catalytic activity of phosphate ion on the mutarotation of D-glucose was studied in a flow injection system in order to determine the coefficient of mutarotation (k, + kz) (AI02), which was obtained from the integrated form of the rate equation

- Peq/Po - 8,) = (kl + k2)t where Bo, Pt, and Peqare the concentrations of the P anomer -1n

(Pt

a t time zero and t and at equilibrium, respectively, and are proportional to the phosphate concentration. The coefficient of mutarotation for the a conformer is about 30% larger than that of the @ conformer. Phosphate traces have been determined by catalytic reduction of Mo(V1) to isomolybdate blue by ascorbic acid in the presence of antimonate-tartrate in a sulfuric medium with hotometric monitoring at 600-700 nm. The method was appied to the determination of phosphorus(V) contents in the range 5 X 10-‘-5 X l P % in high-purity acids (A103). New applications of the iodine-azide system Ting different detection methods were also reported in the rewewed period. Thiamine was determined spectrophotometrically in pharmaceutical preparations by the fixed-time method (t = 11min) (A104). Cystine was determined photometrically in human


447R


blond hair, shee wool, and gelatine on the basis of its catalytic effect on the idne-azide system by monitoring the decrease in the absorbance of iodine at 350 nm and applying the initial-rate and fixed-time methods (A105). Another alternative to the catalytic determination of cystine involves the electrogeneration of the substrate, iodine, by applying a current of 0.8 mA to the generating system and recording the changes in the current of the indicator system for 6-8 min. The latter current is inversely proportional to the amount of catalyst present ( A I M ) . Based on similar principles is a coulometric method proposed for the determination of nanogram amounts of thiourea, glutamine, sulfide, and thiosulfate (A107). Sulfur(I1) compounds (sulfide, thiourea, pyrrolidine-l-carbodithioate, dithizone, and benzothiazole) have also been determined by direct-injection enthalpimetry using the iodine-azide system in nonaqueous media ( A I M ) . The calibration graph, reflecting the resistance changes measured by a thermistor, was linear for concentrations of the different substances in the range 0.5-200 pg. Flow injection analysis with photometric detection and automatic titration techniques have also been used in the determination of mercaptopyrimidines (e.g., thiouracils and thiobarbituric acid) by the iodine-azide reaction, which is induced by these compounds. The detection limit achieved by the FIA technique was 1 ng in 10 pL of sample injected into the reactant stream. The iodine-azide reaction induced by 2-mercaptopyrimidines and 30 homolo ues was investigated; the reaction conditions and the sutstituents on the mercaptopyrimidine ring were found to strongly influence the inducing properties (A109). A photometric flow injection method was used for the determination of sulfide, thiosulfate, and thiourea also based on the iodine-azide system (A110). Under optimal flow conditions, the detection ranges for sulfide, thiosulfate, and thiourea were 0-1 x 0-8 X lo-*, and 0-1.0 X M, respectively. The determination of thiosulfate was not interfered by thiocyanate as the latter did not catalyze the reaction under the experimental conditions used. A kinetic method also based on the iodineazide system was developed to determine the coefficients of partition of thiobenzamide and its 4-methoxy, 4-methyl, 4-ChlOr0, and 4-nitro derivatives in a water/l-octanol medium (A111). By measuring the decrease in the absorbance of iodine at 350 nm, concentrations of the above-mentioned com ounds in the range 0.5-3 pM were determined by the fixextime method ( t = 2 min), with an RSD less than 2%. The determination of organic compounds based on catalyzed reactions usually involves modified catalytic effects or indirect methods. Primary catalytic effects have scarcely been exploited for the determination of organic species, most of which act as bearers for inorganic catalysts. Thus, organic compounds containing iodine have been determined on the basis of their catalytic effect on the Ce(1V)-As(II1) system. The catalytic activity of different compounds of this type (thyroxine (TS, triiodothyronine (TJ, .diiodothyronine, diiodotyrosine, iodotyrosine, triiodoacetic acid, and N-iodosuccinimide) was found to be related to their structure. Several methods based on the measurement of the time required for the potential to change by 15 mV, which was inverse1 proportional to the concentration of the compound, were Lveloped (A112). Stopped-flow photometric and kinetic fluorimetric methods-based on the measurement of the rate of formation of fluorescent Ce(II1)-have also been developed for the determination of T, and T4 thyroid hormones in pharmaceutical preparations (A113). A microassay for the determination of iodide and its application to the measurement of the extent of iodination of proteins and the catalytic activity of iodo compounds was reported by O’Kennedy et al. (A114). The method is based on the iodide-catalyzed reaction between Ce(1V) and As(II1). This rapid assay uses reagents sparingly, is suitable for use with a photometric microplate reader, allows large numbers of samples to be processed simultaneously, and overcomes problems derived from the use of radiolabeled compounds for measuring the extent of iodination. The method was used to determine the conjugation of an iodine-containing hapten to ovalbumin and human serum albumin and to study the relative molar catalytic activity of thyroxine and 4-iodophenol among other compounds. Organic compounds containing metals can also be determined in a similar way. Thus, one flow injection fluorimetric 448R


method for the determination of amino acids relies on the accelerating effect of the Cu(I1)-amino acid complex on the aerial oxidation of phenyl-2- yridyl ketone hydrazone. With this system, L-histidine can \e determined by its enhancing effect on the catalysis of Cu(I1) on the aforesaid reagent. The calibration gra h is linear over the range 1.26 X 10-’-12.6 X lo-’ M L-histi&ne. The method can be extended to other amino acids including L-cysteine, m-serine, L-alanine, Lglutamic acid, glycine and L-arginine (A115). The fungicide Maneb (manganese ethylenedithiocarbamate) has also been determined by the catalytic effect of the manganese it contains on the Malachite Green-periodate indicator system in the presence of NTA as activator. The stopped-flow technique was used for mixing sample and re ent, and the decoloration of Malachite Green was monitoredsotometrically at 615 nm. The initial reaction rate was found to vary linearly with the Maneb concentration over the ran e 1 90 ng/mL (RSD = 1.3%). The method is almost spec& i d was applied to the determination of the pesticide in formulationsand its residues on grain (A116). Several methods based on the primary catalytic effect exerted by an organic compound itself have been reported. One such method was developed as a students’ laboratory experiment intended for the determination of trace amounts of acetonitrile and oxalic acid in the classroom environment (A117). Acetonitrile is determined by its catalytic effect on the destructive oxidation of Catechol Violet by hydrogen eroxide, which is monitored through the decreasing absorgance at 450 nm. The calibration graph is linear over the M. Oxalic acid is determined in much range 5 X 104-5 X the same way, by its catalytic effect on the oxidation of ferroin by Cr(VI), which is measured by monitoring the absorbance at 510 nm. Another method based on a primary catalytic effect allows the photometric determination of amines and nitrosamines (methyl, dimethyl, and trimethylamine, diethylamine, and diethylnitrosamine) at the nanogram per milliliter and picogram per milliliter level, respectively. It is based on their catalytic effect on the oxidation of 1,2,4-triacetoxybenzene (Pyro all01 A) by hydrogen peroxide (A118). The method was usef to investigate the destruction of nitrosamines (dimethylnitrosamine) in drinking water. Dialkyl (e.g., dieth 1) esters of P(OH), catalyze the oxidation of ophenyleneJamine by hydro en peroxide (A119). Under the optimum experimental confitions, the reaction rate, determined by measuring the absorbance at 435 nm 20 min after mixing the reactants, is linearly related to the analyte concentration over the range 1-10 mM. Catalytic fluorometric methods allow the determination of riboflavine and riboflavine 5’-phosphate at the nanomolar level (A120) and of diaminoacridines (acriflavine, rivanol orange, acridine yellow, and proflavine) (A121) at micromolar concentrations. The methods are based on the measurement of the rate of photoreduction of these compounds by EDTA in the presence of the Fe(II1)-1,lO-phenanthrolinesystem, with spectrophotometric monitoring of the ferroin yielded. The methods were applied to the determination of the abovementioned compounds in pharmaceuticals (vitamin Bz, acriflavine, and rivanol), foods, and rat tissues. Some organic compounds can be determined by indirect catalytic methods. Such is the case with adrenaline and noradrenaline, which were determined in pharmaceuticals on the basis of their reaction with a chloroform solution of iodine under buffered conditions (pH 5.5) (A122). The iodine yielded, the concentration of which was roportional to that of adrenaline present in the sample, actexas a catalyst in the oxidation of arsenite by Ce(1V). The system was monitored photometrically at 375 nm and application of the initial-rate method permitted the determination of adrenaline and noradrenaline in the ranges 5-25 pg and 3-30 pg, respectively (RSD = 2%).

B. KINETIC METHODS BASED ON ACTIVATION OR INHIBITION OF CATALYSIS The use of methods based on the modified catalytic reaction rates implemented by addin activating or inhibitory substances allows kinetic methois to be extended to the determination of species that normally exhibit no catalytic properties. Methods for the determination of catalysts relying on


the presence of an activator were included in the preceding section. Inhibitory substances, on the other hand, are chiefly used in catalytic titrations. Hence this section deals with the kinetic determination of activators and inhibitors. Phosphorus-containin com lexones can act as activators n(Ilf-cad oxidation d of o-dianisidine or inhibitors on the M by KIOI. Thus, nitrilotrimethylenephosphoricacid (NTPA), eth lenediaminotetramethylenephosphoricacid (EDTPA), a n 8 diethylenetriaminopentamethylenephosphoric acid (DTPPA) exert inhibitory effects, the magnitude of which increase with the dentate number, while iminodimethylenephosphoric acid (IDPA) enhances the catalytic activity of Mn(I1) in the reaction. These substances can be determined at concentrations on the order of lo-’ M by a kinetic method. Also, the activatin effect of IDPA has been exploited in the determination of dn(I1) by monitorin the absorbance at 440 nm and applying the fixed-time metiod t = 1 min). The detection limit thus achieved was 5 X 10- (BI). Activation. Methods relyin on the activating effect of metal and nonmetal ions on cadyzed reaction were reported in smaller numbers than those involving organic compounds in the reviewed period. A kinetic fluorometric method for the determination of zirconium(IV) was proposed by Medina et al. (B2).It is based on the activating effect of this ion on the Mn(I1)-catalyzed aerial oxidation of Morin. The reaction is monitored by measuring the fluorescence decrease at 417 nm. Under the optimized experimental conditions used, the calibration graph is linear up to 250 ng/mL of Zr(1V) and the RSD is less than 3%. The method is interfered by Be, Cu, and Mg. The activating effect has been exploited to unprove the selectivity of the kinetic fluorimetric determination of Mn(I1) by about 50% [detection limit, 0.26 ng/mL Mn(1I)I. The optimum conditions for the photometric determination of micro amounts of phosphorus-containing complexones were studied on the basis of their activating effect on the oxidation of o-phenylenediamine by hydrogen peroxide, catalyzed by Ti(IV) and Mn(I1) (B3). Several methods were also developed for the determination of hydroxyethylydenediphosphoric acid in air, urea, and water. The enhanced fluorescence of the 1,1,3-tricyano-2-amino1-propene (TRIAP)-Cu(II)system resulting from the presence of’ histidine and pilocarpine has been exploited for the determination of histidine in the range 10-5-104 M (B4)and of pilocarpine between 2 and 125 pg mL. The method was successfully applied to analysis or the two analytes in ophthalmic solutions (B5). The accelerating effect of the two substances was kinetically studied and various kinetic methods (fixed time, initial rate, variable time) were tested. Flavonoids exert an activating effect on the aerobic oxidation of 2-hydrox a hthaldehyde thiosemicarbazonein the presence of Mn(IIywgich acts as a catalyst. The reaction is monitored spectrofluorimetricallyby measuring its initial rate at the excitation and emission wavelengths of the resultin oxidation roduct. The reactivity of 14 flavonoidswas studiei and fount! to be related to their structure. Very sensitive methods (e .,the calibration raph was linear between 0.25 and 12.5 1.1 quercetin) were evelo ed, as were determinations of the flavonoids in tea and red!wine using fecalase and hesperidinase (B6). Inhibition. Several contributions to the kinetic determination of nonmetal and metal ions were reported over the reviewed period. Thus, a kinetic catalytic method for the determination of iodide with the Ce(1V)-As(II1) system (B7) bearing more than a passing resemblance to the braked catalytic titration mode was proposed. It involved the addition at a constant speed of a given volume of a mixture of inhibitor and substrate [Hg(II) and Ce(IV), respectively] over the catalyst and an excess of the other component of the indicator reaction [iodide and As(III),respectively]. D the addition step, the reaction develops while the c a t a l y s z l w k e d . The extent of reaction development is monitored by measuring the absorbance of unreacted Ce(1V) a t 318 nm. Ideally, .the reaction is stop d after a stoichiometric amount of inhibitor has been adderHowever, if further Hg(I1) is added at that point, the absorbance due to Ce(1V) remains constant and is inversely proportional to the initial iodide concentration. While in the catalytic titration mode the iodide concentration must be relatively high since the substrate must be rapidly consumed, even in the vicinity of the equivalence point-where

6

d

if

d

the catalyst is almost completely blocked-this methods allows smaller amounts of iodide (between 0.05 and 220 ng/mL) to be determined over various ranges depending on the Hg(I1) concentration and addition speed used. A novel kinetic method for the determination of trace chloride based on the oscillatin reaction between bromate, malonic acid, and Ce(1V) as iniicator system was reported (B8). The chloride ion prevents the regeneration of the catalyst, which in turn decreases the amplitude and increases the period. Such a decreased amplitude and the chloride concentration are linearly related over the range 104-104 M. The method was applied to the determination of trace chloride in human serum. The well-known indirect catalytic method for determination of fluoride based on the zirconium-catalyzed oxidation of iodide by sodium perborate was modified by using a lower perborate concentration and omitting ascorbic acid with no loss of sensitivity or accuracy (B9).Fluoride was also determined by an indirect photokinetic method based on the inhibitory effect of the halide on the Fe(I1)-catalyzed photoxidation of thionine. The rate of the reaction was monitored by measuring the absorbance decrease at 600 nm after irradiation for a preset time. The calibration raph was linear over the range 38-228 ng/mL and the methodi was successfully applied to the determination of fluoride in mineral waters

(BIO).

A kinetic thermometric method for the determination of Hg(I1) based on its inhibitory effect on the iodide-catalyzed reaction between Ce(1V) and arsenite was developed and contrasted with its cold vapor atomic absorption s ctrometric counterpart ( B l l ) . Though somewhat more la#kious and time consuming than the standard method, the proposed method was less ex ensive to implement and allowed the determination of HglI) in the range 2-10 ng/mL by injecting 1mL of an iodide solution containing 800 ng. The use of the reduction-aeration preconcentration technique allowed mercury to be determined at the nanogram per milliliter level in sea and drinking water. Mercury vapor was also determined in air b the iodine-azide reaction, induced by sodium diethylditgiwarbamate (DDTC) (B12).After the sampling and sample pretreatment, 1.25 Mg of sodium DDTC was added to the mercury solution and the H -DDTC complex formed was extracted into CC1 . Unreactec! DDTC was determined coulometrically with t i e iodine-azide system. The method allowed the determination of mercury at concentrationsbetween 0.01 and 0.05 ng/m3 in air. The Pd(I1)-catalyzed reaction between Pyronine G and HzPOf was exploited for the determination of arsenite, which acts as an inhibitor. Under the optimized experimental conditions used, As(II1) was determined over the range 6.2-62.6 ng/mL. The method was also applied to the determination of arsenite as an impurity in various chemicals (B13). Ma nesium ion inhibits the formation of the blue product of thehn(I1)-catalyzed oxidation of succinimide dioxine. This effect was used for the determination of the alkaline earth at concentrations between 0.5 and 8 Fg/mL by flow injection analysis with photometric detection at 695 nm (B14). Nitrilotriacetic acid and NaOH were used as masking agents for other alkaline-earth metals and up to 150 rg/mL Ca and Sr and up to 300 Mg/mL Ba ions did not interfere the determination of 5 p /mL Mg ion. The RSD of the method, which was satisfactorivy applied to the determination of magnesium in drinking water and common salt, was 2%. Few methods for the determination of organic compounds as inhibitors of metal-catalyzed reactions were reported over the reviewed period. One such method is based on the inhibitory effect of codeine on the catalytic decomposition of which was used for the hydrogen peroxide by Co(I1) (B15), determination of the inhibitor in pharmaceutical preparations. The effect of codeine was enhanced by the presence of 5% ethylene glycol. The reaction was monitored spectrophotometrically and the method allowed the determination of codeine in the range (0.8-2.4) x lob M. Diamorphine, morphine, and papaverine interfered at concentrations above that of codeine. However, 2-fold excess of diomin and thebain, 3-fold amounts of caffeine, and 4-fold concentrations of noscapine were tolerated. Another method involving the use of organic compounds as inhibitors was developed for the determination of 8-quinolinol, which inhibits the Cu(I1)-catalyzedoxidation ANALYTICAL CHEMISTRY, VOL. 62, NO. 12, JUNE 15, 1990

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of 4,4-dihydroxybenzophenonethiwmicarbazone b hydrogen peroxide (B16).Quinolinol forms a chelate with 8u(II), and the rate of ap earance of the absorbance at 415 nm of the oxidation p r o h c t generated in a reaction catalyzed by unreacted copper is roportional to the concentration of 8quinolinol. The caIbration gra h is linear over the ran e 8 x 10-'-4 X 10" M, and the RgD achievable is 2%. !'he method compares favorably in terms of sensitivity with other recently reported photometric methods.

C. TITRIMETRIC METHODS WITH CATALYTIC END-POINT INDICATION Catalytic thermometric titrations for indication purposes have been discussed in an overview of titrations in nonaqueous solvents including fundamental studies and titrations of organic substances (Cl).Zhang and Gu devised and studied the performance of a spectrophotometric titrator consisting of a spectrophototitrating unit, a calculation unit, a constant-speed burette, and a potentiometric recorder (C2). The most significant specifications of this device are as follows: titration rate, 0.2-5 mL/min; drawing rate, 5 mL/min; absorption detection sensitivity, 10.0005absorbance units (in the ran e 0-0.4 units); photometric spectral range, 380-800 nm. TEe instrument was satisfactorily tested on catalytic precipitation (titration of Ag(1) with standardized KI) and catalytic complex formation reactions (titration of Ca(I1) with standardized EDTA). The above authors also reported a direct titrimetric method for determination of metal ions with EDTA using a ligandexchanpe reaction-rarely used in catalytic titrations-for indication purposes (C3). The Ni-trien/Cu-EDTA system, which is catalyzed by trace amounts of EDTA, is the basis for the determination, in which the Cu-trien yielded is used as indicator and is monitored spectrophotometrically at 550 nm. The method allows the determination of Cu, Ni, Zn, Pb, and Ca at the micromolar level in buffered borax solutions of pH 10.0. The proponents of the method also reported a study on the factors influencing the abrupt chan es observed in the catalytic titration of metal ions with EbTA by the ligand-exchange reaction used. The slope of the abrupt portion of the titration curve (tan8)was used to characterize the rate of the indicator reaction. An approximate theoretical equation relating tan 8 linearly to the initial concentration of Ni-trien, the speed of EDTA addition, and the rate constant of the reaction between EDTA and Ni-trien was derived to account-satisfactorily-for the experimental results (C4). Various metals can be determined with indirect catalytic end-point detection. Thus, Cr(II1) can be determined at concentrations between 2 and 20 mg by reaction with excess EDTA and subsequent back-titration with a standard Cu(I1) solution, the indicator reaction being the Cu(I1)-catalyzed decomposition of hydrogen peroxide, the end-point of which is detected biamperometricall (C5). Manganese, cadmium, and lead were also determine$ by a semiautomatic catalytic photometric titration method using EDTA as inhibitor of the Cu(I1)-catalyzed aerial oxidation of dimedone diguanylhydrazone. The method was applied to the determination of P b in brass ((26). The total hardness of drinking water has been determined by a semiautomatic catalytic titration method based on the oxidation of salicylaldehyde guanylhydrazone by hydrogen peroxide in the presence of Mn(I1) as titrant-catalyst and DCTA as inhibitor of Ca and Mg (C7). In the above-mentioned organic redox titration methods, metal ions are usually determined indirectly, using the catalyst as titrant. However, a different approach known as catalytic titration by substrate inactivation has been applied to the direct photometric titration of mercury (C8). This metal inhibits the oxidation of 4,4'-dihydroxybenzophenone thiosemicarbazone (DBPT) by hydrogen peroxide in the presence of Co(II), a catalyst for this reaction. DBTP is used to titrate a solution containing the mercury, the oxidant, and the catalyst. The calibration curve obtained by plotting the titrant volume added against the Hg(I1) concentration is linear over the mercury concentration range 0.03-0.7 pM. The method was satisfactorily applied to the determination of inorganic and organic mercurials (phenylmercury derivatives) in pharmaceutical preparations after pretreating the samples. Mixtures of cystine and cysteine have been resolved by using 450R


this catalytic titration mode on the basis of their counterinhibitory effect on mercury. The experimental rocedure involves two titrations only differing in the aadition of hydroxylamine in one of them and was applied to the determination of the two amino acids in urine (C9). Silver sulfadiazine was determined in harmaceutical reparations (Dermazin cream) with no samp e pretreatment gy a catalytic end-point method using the iodide-catalyzed Ce(1V)-As(II1) system in a sulfuric medium. The course of the titration was monitored by catalytic controlled-current potentiometry with a glassy carbon indicator electrode and the results obtained were contrasted with those found by classical otentiometry using a silver or gold indicator electrode. T i e RSD was less than 0.9% for 0.7 mg of Ag (i.e., 2 mg of sulfadiazine) (C10). Finally, barbital and phenobarbital were determined by a catalytic thermometric titration method using a nonaqueous solvent. Each substance was dissolved in 1:l DMF/acrylonitrile and titrated with KOH in isopropyl alcohol, with a 2 "C/min temperature increase as the end-point. The recovery was 100% in both cases (C11).

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D. KINETICS AND MECHANISMS OF SOME CATALYZED REACTIONS OF ANALYTICAL INTEREST Oscillating chemical reactions are arousing a growing interest from chemists, physicists, biologists, and engineers on account of their usefulness in solving engineering and industrial problems such as those posed by the operation of chemical reactors or biotechnological systems. In addition, these reactions have aroused the interest of biologists since the model certain biochemical and even biological rocesses sucg as the development and spread of spatial oscilLtions in different media. On the other hand, the use of the flowthrough technique in conjunction with continuous mixin allowed a large number of new oscillating reactions to be f o w i and Belousov-Zhatbotinksi (BZ) reactions and other already known oscillating reactions to be studied in greater detail. Yatsimirskii recently reviewed oscillating chemical reactions in terms of their basic features and prospects for use in analytical chemistry (01). The bromate-cerium-oxalic acid oscillating system, a representative example of BZ reactions, was simulated (02) and assumed to be controlled by bromide hydrolysis. A radical chain reaction between HBrO and oxalic acid and the formation of HC02- on reduction of the Ce(1V) were assumed to occur. Under certain conditions, the oscillating behavior was consistent with the experimental results. The dispro ortionation of hydrogen peroxide catalyzed by the iodateio&e pair in a sulfuric medium is another example of a recently elucidated oscillating reaction (03). The time evolution of the process and some kinetic parameters were reported. Another recently reported oscillatin reaction involves the permanganate-nitrite-formic acid-met%anol oscillator, which contains nonhalogen compounds and is the first example of nitrogen-based oscillators studied so far ((04). The singular properties of this system were discovered while mixing aqueous solutions of the above reactants in a well-stirred continuous-flow tank reactor. The authors sug ested that, on the onset of the process, permanganate was rAuced to m anew dioxide by formic acid; in a second step, the dio%e was reduced by nitrite ion; finally, manganous ion was oxidized to permyanate, thereby establishing an autocatalytic process which mig t be the key mechanism of the system insofar as autocatalytic reactions play an essential role in chemical oscillation. Decomposition of H2OP Several kinetic studies on the decomposition of hydrogen peroxide catalyzed by various metal-li and com lexes were re orted over the reviewed period. bhus, Rizfalla et al. stu8ed the kinetics of the decomposition of H202catalyzed b ethylenediaminetetrakis(methylenephosphonate)iron(III)$5).The observed rate law, which included the acid dissociation constant of the aquo complex, and a mechanism in which the aquation of the ternary hydroxo complex was the rate-determining step were also reported, as were some kinetic and thermodynamic parameters, which were contrasted with previously reported data on the catalysis by structurally related Fe-EDTA species. The


same authors performed a kinetic study of the reaction between hydrogen peroxide and the l-hydroxyethylyldene-1,ldiphosphonate-iron(II1) complex in a KNO medium and reported various data of analytical interest (b6) The rate of decomposition of hydro en peroxide by the Fe(II1)-EGTA complex was investigate8 under different experimental conditions (pH, temperature, water-miscible solvents, and HzOz,iron complex, and acetate ion concentration). The rate law and a detailed reaction mechanism were reported (07). On the other hand, further studies on the kinetics and mechanism of the decomposition of hydrogen peroxide catalyzed by the copper-imidazole complex were also reported (08).The kinetics of the process, linked to the rate of evolution of oxygen, revealed the involvement of a ternary Cu(11)-imidazole perolro complex in the rate-determinin step. The e uilibrium constant of the coordination of hyfrogen peroxiae to the cupric ion and the acid dissociation constant of the coordinated HqOzligand were found to be 1.7 M-' and 2.1 x lo4 M, respectively. The ternary complex underwent an intramolecular electron transfer (k = 4 s-') to yield the Cu(1) species, which then reacted with hydrogen peroxide or dioxygen to restart the catalytic cycle. A comprehensive mechanism based on the kinetics of evolution of oxygen and the electrocatalytic behavior of the copper-imidazole complexes under a dioxygen atmosphere was proposed. Systems of Biological Interest. Reactions between ferrous complexes and hydrogen peroxide (Fenton reactions) have been reported to be a source of hydroxyl radicals, which are harmful to living cells. However, there is only indirect evidence that hydroxyl radicals can form under normal biological conditions. A stopped-flow spectrophotometric study of the intermediates yielded in the reaction between ferrous 01 aminocarboxylate complexes [Fe(II)-EDTA, Fe(I1)ETSA, and Fe(I1)-HEDTA) and Hz02in the presence of various scavengers (ethanol, formate, benzoate) provided direct evidence of the occurrence of a non-hydroxyl radical intermediate in some of the systems considered (09). The immediate implication of this finding in connection with biological systems is that Fe(I1) eroxo or ferry1 complexes may cause oxidative damage at t i e bindin site rather than via short-lived, indiscriminate hydroxyl ragcal intermediates. A mechanism for each of the processes involved was proposed. The abilit of scavengers to reveal the roduction of hydroxyl radi& in the iron-catalyzed Haber-Geiss reaction was recently investigated and four methods of determination for such radicals were evaluated (010). The catalytic and immunochemical properties of the ferritin-horseradish peroxidase (HP) conjugate were also studied (011). The kinetics of the oxidation of o-dianisidine at 15-37 "C by the conjugate showed the rate constant to be 1.75 times larger than that of the reaction catalyzed by the enzyme alone at 40-65 "C. The conjugates were stable in the acid medium used. The ferritin-HP conjugate can be used for immunoenzyme assays of ferritin. Reactions Catalyzed by Transition-Metal Ions. Although great endeavors have been devoted to the elucidation of the mechanism via which a-amino acids are oxidized by ermanganate ion in strongly acid media, there is a relative Pack of information about the same process in neutral and alkaline media. As a result, mechanistic reports on this type of reaction are normally limited to the pathway via which the cationic form of the amino acid is o x i d e , while the reactivity of the zwitterionic and anionic forms is normally ignored. In order to gain a better understanding of the oxidation mechanism, Brillas et al. (012) undertook a kinetic study of the reaction between 2-threonine and permanganate ion in a neutral aqueous buffer. The results showed this reaction to be autocatalyzed by colloidal MnOz,.which was stabilized in solution by adsor tion of phosphate ions on its surface. The rate constants of 10th the noncatal ic and the autocatalytic reaction pathways were determine by integral and iterative methods, so was the contribution of the zwitterionic and anionic forms of the amino acid to the rate of the noncatalytic oxidation. The mechanisms proposed for the two reaction pathways were quite consistent with the kinetic results reported. The kinetics and mechanism of the autocatalytic oxidation of Fe(phen) and F e ( b p ~ ) ~by%HN03were studied by Barna et al. (0135,who applied the general mechanism of autocatalytic nitric acid oxidations to fit single experimental curves

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and all concentration dependences. The mechanism proposed was supported by the good agreement between the experimental results and those obtained by numerical integration of differential rate equations derived from the reaction scheme. Pentacyanoferrate coupling reagents are known to significantly accelerate the reaction between ammonia and hypochlorite (Berthelot reaction), which is of great analytical interest for the determination of ammonia. However, no descriptive mechanism has so far been proposed for this reaction. Harfmann and Crouch (014) studied the steps seemingly involved in the Berthelot reaction in the presence and absence of coupling reagents. The first step, involvin the interaction between hypochlorite and ammonia to yield p$H2C1,was found to be of second order, with a rate constant of 3.2 X 106L mol-' 8-l. The formation of benzoquinone chlorimine, yielded upon reaction between phenol and NH,Cl, in a second step was first evidenced; the rate of this step was found to be affected by the presence of pentacyanoferrate compounds, in the absence of which it was the rate-determining step. This type of compound has little or no effect on the Berthelot reaction involving chlorimine and phenol, which yields indophenol blue. The Fe(I1)-catalyzed photoreactions of aldo- and ketohexoses (015)and the TiC1,-catalyzed photoreactions of aldohexoses (016) were inter reted in terms of photoinduced electron transfers within a cKelate of iron or titanium ion with the carbohydrate molecule. A detailed study of the kinetics and mechanism of the autoxidation of 2-mercaptoethanolto 2-hydroxyethyldisulfide, catalyzed by the Co(II)-4,4',4",4''-tetrasulfophthalocyanine in an aqueous medium was reported by Leung and Hofmann (017). The active catalytic site was a dimer bridged to 2merca toethanol. Hydrogen peroxide and 2-mercaptoethanol radicays were identified as reaction intermediates. This catalytic autoxidation of 2-mercaptoethanol and other mercaptans by the cobalt complex can be exploited for the selective determination of this type of malodorous, hazardous compound occasionally occurring in waste water. The kinetics and mechanism of the uncatalyzed and Hg(11)-catalyzed oxidation of aspartic acid by Chloramine T was found to take place via a complex formed between the mercury and aspartate ion, which potentiates the catalytic action of the metal (018). The negligible salt effect encountered pointed to a mechanism involving a neutral molecule and an anion in the rate-determining step. Rate laws consistent with the experimental results were reported. Reactions Catalyzed by Noble Metals. The use of oxidants other than potassium peroxydisdfate in Ag(1)-catalyzed reactions is far from frequent. However, the kinetics and mechanism of the silver-catal zed oxidation of L-alanine, L-valine, and L-leucine b Ce(fV) in a nitric medium were studied in depth (019). Jhis reaction is first order in Ce(IV) and the amino acid, and its rate increases linearly with the Ag(1) and "OB concentrations-added KNOB exerts a moderate retarding effect. The plots of k versus the amino acid concentration and of their respective reci rocals have a zero intercept in the case of leucine and valine, \ut the curves run for alanine have a nonzero intercept, which is indicative of a Michaelis-Menten relationship and hence of the formation of a complex between Ag(1) and the amino acid in the initial

st?? omparatively few contributions to the study of Os- and Ru-catalyzed reactions were re orted over the last 2 years. One such contribution describexthe kinetics and mechanism of the Os(VII1)-catalyzed oxidation of alkanals by hexacyanoferrate(I1)(020). The study of the kinetics of oxidation of ethanal, propanal, and n-butanal by hexacyanoferrate(II1) in a sodium carbonate-bicarbonate buffer in the presence of Os(VII1) showed the reaction to be zero order in the oxidant, first order in the alkanal and Os(VIII), and a fractional order (-0.5) in the alkali. The results su gested that the anion of the alkanal hydrate was involved in t8e oxidation process. The authors evaluated a number of thermodynamic parameters. The kinetics and mechanism of the Ru(II1)-catalyzed oxidation of organic sulfides and tri henylphosphine by Nmethylmorpholine were studied in fepth by Kuriacose et al. (021),who found the process to be first order in the catalyst and the oxidant. The order in the substrate, however, varied between a fractional number at low concentrations and zero at sufficiently high concentrations. A spectro hotometric study revealed the formation of a 1:l complex I! etween the ANALYTICAL CHEMISTRY, VOL. 62, NO. 12, JUNE 15, 1990

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substrate and the catalyst. A mechanism consistent with the experimental findings was put forward and verified. The oxidation of water to molecular oxygen, which involves the transfer of an overall four electrons, is of great relevance as it provides a means of converting luminous energy into chemical ener -converting solar energy into that of chemical fuels seems to% the most promising alternative to its storage. In this respect, the use of water as an electron donor (e.g., water oxidation) is of crucial significance,as is photosynthesis in nature. On the basis of studies reported so far, it seems logical to think that polynuclear complexes [e.g., those of Ru(II)] are the only serious candidates for use in water oxidation processes which, as stated above, involve the exchange of four electrons. However, Kaneko et al. ( 0 2 2 ) found that mononuclear ruthenium ammine complexes catalyze oxygen evolution in the presence of Ce(1V) via water oxidation, both in a homogeneous and in a heterogeneous state. The electrochemical properties of these ruthenium ammine complexes allow them to be used as two-electron oxidants in water oxidation. The oxy en evolution was confirmed by using the H2**0isotope in t e reaction medium. The water oxidation process was found to be influenced by the ionic strength of the medium, and the O2yield was found to increase with the medium acidity. Heterogeneous catalysis with the Ru complex adsorbed in kaolin clay was as effective as the homogeneous catalysis. A reaction mechanism was put forward and discussed. A study of the hydroformylation of 1-hexene with homoeneous rhodium catalysts was reported by Hanson and Davis $023). Atwood (024) recently reviewed the use of organoiridium complexes as models for homogeneous catalyzed reactions. On the other hand, the kinetics of oxidation of mono-, di-, and trichloroacetic acid by Chloramine T in the presence of Ir(II1) as a catalyst in acid media was also recently studied ( 0 2 5 ) . Both the Ir(II1)-catalyzed and the uncatalyzed oxidation reaction were studied in depth and the reaction order in each reactant was determined. The process was f i t order in Ir(III), while the influence of the salt content and the solvent used was negligible. A plausible mechanism and rate laws consistent with the experimental results were given for the catalyzed and the uncatalyzed rocess. Reactions Catalyzed by &her Species. Oxalic acid was found to behave anomalously in its reaction with bromate ion in the presence of Ce(II1) as a catalyst in a perchloric-sdfuric . the other hand, the HgBr+ and H Br2 acid medium (026)On species formed were recently shown to hinder the autoca ytic reaction between bromate and Ce(II1) and hence the occurrence of oscillations. A kinetic and mechanistic study of this process in the presence of mercury acetate was reported. In the presence of Hg(I1) as a bromide scavenger, the reaction was found to be second order in bromate and the acid and 0.4 and zero order in Ce(II1). However, the kinetic behavior of oxalic acid was anomalous: its reaction order was -0.7,0, and 1.4. The chemistry underlying the phenomena involved was discussed by the authors. Finally, Subba Rao et al. ( 0 2 7 ) studied the kinetics of oxidation of benzeneazodimethylaniline and Methyl Orange by chromic acid in the presence of 1,lO-phenanthroline and 2,2’-bipyridyl. The spectrophotometricdata obtained revealed the reaction to be first order in both reactants. The reaction was catalyzed by H+ ions, the reaction order of which was unity in both cases. 1,lO-Phenanthroline was found to exert a stronger catalytic effect than 2,2’-bipyridyl. The former, though not the latter, was found to respond to a Michaelis-type kinetics, which is a rare occurrence in chromic acid oxidations. A plausible mechanism accounting for the catalytic behavior of the two ligands was proposed. E. KINETIC DETERMINATIONS BASED ON ELECTRODE REACTIONS AND PROCESSES Conventional electrochemical detection in continuous-flow systems (includingchromatography), altho h certainly made under dynamic conditions, is not discuss8 in detail in this part of the review. More coverage can surely be encounter in the reviews on chromatography and electroanalytical determinations. The bulk of this section emphagizes electrocatalysis, an area that is experiencing renewed impetus as a result of increasing interest in chemically modified electrodes and biosensors.

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The electrode kinetics of poly(o-phenylenediamine), poly(N-methylaniline), and poly(N-ethylaniline) films, deposited on basal-plane pyrolytic graphite surfaces by oxidative electropolymerization,has been reported by Chiba et al. (El). The rate of charge transfer through the films in chemically modified electrodes of this type determines their usefulness as electron-transfer mediators (or catalysts) in anal ical applications. The c clic voltammetric responses o f t ese films were similar to d o s e observed for reversible, simple redox processes at a solution/uncoated interface. A plication of normal pulse voltammetric measurements led t i e authors to concur that (1) heterogeneous electron transfer at the electrode/film interface obeys the Butler-Volmer equations and (2) homogeneous charge transport within the film can be described by Fick’s laws of unidirectional diffusion. Of incidental interest to this type of chemical modification of conducting surfaces is a review on electrodepositionof polymer coatings by Beck (E2). The effect of counterion concentration, temperature, and sweep rate on the cyclic voltammetric response of multilayer tetracyanoquinodimethane and poly(vinylferrocene) polymer-coated electrodes was reported by Inzelt and Bacskai (E3). Oxidative electro olymerization of tris[5-amino-1,10phenanthroline]iron$I) at carbon paste, glassy carbon, and platinum electrodes has been discussed by Nyasulu and Mottola (Ed). The polymerization carried out in acetonitrile solutions produces stable films with competitive charge transfer kinetics across the film and with little configurational change. These characteristics ointed to the Fe(II)/Fe(III) immobilized centers so obtainetfas useful sensing surfaces for electrocatalytic detection/determination of oxidizin and reducing species. Such usefulness for the detection of r$02(g) was demonstrated by Bonakdar et al. (E5). The olymercoated lassy carbon electrodes were compared wit carbon paste ekctrodes modified by direct admixing of perchlorate cation salts of tris[4,7-diphenyl-l,lO-phenanthroline]iron(nII) (E5),described earlier by Hynes et al. (E6). Electrocatalysis at these modified surfaces bearing immobilized Fe(II)/Fe(III) centers was discussed, and the detection of H S(g), C1 (g), and S02(g)reported, by Bonakdar and Mottola ?En.Tkese applications performed in continuous-flow systems and without debubbling before detection show that the continuous “bathing” of the sensor surface with sup orting electrolyte, under predominantly laminar flow con&ions, ensures the presence of an unbroken film of ions to support electrical mi ation and satisfy electroneutrality requirements. A glassy cagon electrode was modified with a mixed nickel-iron cyanide film and was used for a very selective electrocatalytic detection of Fe(II1) after liquid chromatographic separation (Ea). Electropolymerized films of bis(viny1terpyridine)cobalt(I1) on glassy carbon surfaces exhibit catalytic activity for the reduction of carbon dioxide and oxygen (E9). The predominant product of carbon dioxide reduction is then formic acid. Reduction of oxygen gives water as predominant product at high polymer coverage and hydrogen peroxide at low cov-

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er?:balt in aqueous solutions in the 104-10-4 M range was determined at carbon paste electrodes admixed with 1,lOphenanthroline in batch systems using cyclic and differential pulse measurements (EIO). The upper concentration limit is controlled by the kinetics of charge transport within the carbon paste. A few papers have been published exploiting, for deters, catalytic waves at mercury drop electrodes. minative pur coupled catalytic hydrogen discharge with Wang et al. interfacial accumulation of the catalyst to enhance the sensitivity of some voltammetric measurements. The approach was illustrated with the determination of platinum but can also be applied to that of organic species showing adsorption-dependent electrocatalysis. A method for the determination of 10-6-104% platinum and osmium in sulfite ores in the presence of large amounts of palladium has been proposed by Medyantseva et al. (El2). The method extracts the metals into naphthalene with sodium 2-methyl-&mercaptoquinoline, dissolves the extract in a dimethyEormamide/buffer (pH 2.75) medium, and uses the catalytic hydrogen currents polarographically obtained for the determination. Lipoic acid and lipoamide adsorb on a hanging mercury drop electrode and give a catalytic hydro en wave in ammonia buffer (pH 8-9.5) containing Co(I1) $13). This has been

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utilized to determine these biochemicals in aqueous solutions in the 2-10 nM concentration range. Molybdenum(VI) at the 10-6-10-8 M level has been determined by a catalytic polaroraphic method in a salicylaldoxime/bromate ion/acetate uffer system (pH 4.7) (E14).The method was applied to steel samples after removal of iron by solvent extraction into ethyl ether from about 6 M HCl. Chromium(V1) and chromium(II1) have been determined in natural water samples exploiting the kinetic effect of NOzon their polarographic waves at a pH of 9.0-9.2 (E15). Electrocatalysis resultin from homogeneous electron transfer between an electro e-generated anion radical of an inert nickel or cobalt chelate and a chlorinated organic substrate (e.g., methoxychlor, chlorophos, chloroform, and dichloroethane) in dimethylformamide has been proposed for the indirect determination of the chlorinated species at the 10-s-10-6 M level (E16). Electrodeposition of platinum particles into polyaniline films on laas carbon electrodes results in surfaces of catalytic activity for txe reduction of h drogen and the oxidation of methanol (E17). Electrocata$sis a t spectroscopic-quality a hite modified b adsorption of methylene blue, thionine, Beydola blue, and pienazine methosulfate has been described (El&?).Batch and flow evaluation of the resulting surfaces for sensing myoglobin and hemoglobin is presented. Adsorption-based polarographic catalytic currents permit M (E19). determination of Co(I1) down to a limit of 3 X These currents are observed in s stems containing Co(I1)nioxime-NO;; nickel and zinc can tolerated in large excess. Electrocatalyticoxidation of polyhydroxy compounds has been observed at a glassy carbon surface modified by deposition of a Cu C1-containing crystalline species (E20). Nanomolepicomo e quantities can be detected.

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F. APPLICATIONS OF LUMINESCENCE The Februar 15,1988, issue of Analytica Chimica Acta

(FZ)is totally fiedicated to the Proceedings of the 2nd International Sym osium on Quantitative Luminescence Spectrometry in 8iochemical Sciences. Most of the papers in this issue have angles of analytical interest with kinetic im lications. !he use of chemiluminescence to distinguish between free Cr(II1) and Cr(II1) bound to chelate-forming carboxylate ligands such as oxalate, citrate, phthalate, salicylate, and tartrate has been demonstrated by Huizenga and Patterson (FZ).Reaction rate coefficients for metal chelate formation are reported and complexation with humic acid discussed as well as a correlation of reaction rates with the nature of the complexing ligand. Postcolumn chemiluminescent detection coupled to liquid chromatxyphy has received some attention; examples of such efforts fo low. Hara et al. (F3) have combined a microbore affinity chromatography column with a chemiluminescence detector for protein. The chemiluminescent postcolumn detection utilized the l,lO-phenanthroIine-HzOz-Cu(II)system. The minimum detectable (injected)quantity for human serum albumin is about 15 ng. Koerner and Nieman (F4) used an indirect postcolumn chemiluminescence detection in the high performance liquid chromatographic ion-exchange se aration of amino acids, reversed-phase separation of catecho amines, and ion-pair separation of gentamicin C components. The Cu(I1)-luminol-H202 reaction is the basis for detection of a decrease in chemiluminescence as a result of the Cu(I1)-analyte interaction. The same authors (F5) used the luminol chemiluminescence to detect the H202 produced by @-Dglucose resulting from glucosides chromatographically separated via reversed-phase HPLC. The separated glucosides (phenyl glucoside, p-nitrophenyl glucoside, and salicin) passe two enzyme reactors se uentially located before the chemiluminescent detection. %he first enzyme reactor hydrolyzes the glucosides using immobilized @-glucosidase;the second reactor, with immobilized glucose oxidase, is responsible for the formation of hydrogen peroxide. Copper(I1) stimulates cathodic subband ap electrochemiluminescence generated by a symmetric doube-step potential (sequential positive and negative pulses with intermittent and 2,2'-bizero-potential steps) in the presence of H202

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pyridine and at an oxide-coated aluminum electrode (F6). This allows a very selective (interferencefrom other metal ions is reported as nonexistent) and sensitive determination of Cu(I1) with a limit of detection in the 5 x lo* M level. Petrea et al. (F7) have illustrated the advantages of timeresolved detection in immunoassays with fluorescent probes. The long fluorescence lifetime of rare-earth metal chelates improves detectability in detection based on fiber-optics technology. Microgram and submicrogram per liter concentrations of seven lanthanides (Sm, Eu, Gd, Tb, Dy, Ce, and Tm) in aqueous solutions have been determined by laser-induced time-resolved fluorescence measurements (F8). Evaluation of solid supports for use with room temperature phosphorescence has received special attention. A comparative study of room-temperature phosphorimetry of polyaromatic hydrocarbons with or anized media and pa er as supports has been published (F97. The authors conclu& that measurements in organized media offer analytical advantages but recognize that their ap lication is limited to compounds of rather low polarity. Pur& and Hurturbise (FIO)compared parameters of analytical interest in the determination of benzo[flquinoline, -aminobenzoic acid, phenanthrene, and 4-phenylphenol a i o r b e d on a variety of surfaces using room-temperature luminescence measurements. Filter paper appeared to be the best inert support overall. Lon and Su (F11)have evaluated a polyamide and crystalline cefiulose as inert supports for analytical applications of room-temperature phosphorimetry. The room-temperature phosphorescence, the room-temperature fluorescence, and the low-temperature hosphorescence of biphenyl and some polychlorinted bip enyls have been reported by Khasawneh and Winefordner (F12,F13). Analytical ap lications of the room-temperature phosa phorescence oPcarbary1 (1-naphthyl-N-methylcarbamate, widely used insecticide) adsorbed on Whatman No. 1 chromatographic and Whatman No. 40 filter paper previously treated with water followed by UV exposure to reduce background have been discussed by Campiglia and de Lima (F14). Enhancement of room-temperature phosphorescence of polyaromatic hydrocarbons adsorbed on paper by anionic surfactants has been reported by Ramis Ramos et al. (F15). Cationic surfactants totally quench the emission of radiant power. Selective enhancement was also observed on treating the filter paper with cyclodextrins (F16-18). Burrell and Hurturbise (F19) reported on the room-temperature fluorescence and phosphorescence of benzo[fl quinoline and benzo[h]quinoline adsorbed on silica gel TLC plates submerged in chloroform/n-hexane. Protection from collisional deactivation was observed. Anthracene at nanogram levels can be determined by room-temperature phosphorescence on Whatman No. 1 filter paper impregnated with thallium(1) lauryl sulfate (F20). The long alkyl chains in the lauryl sulfate seem to prevent quenching by oxygen. The attractive features of phosphorescence and delayed fluorescence species as alternatives in room-temperature luminescence immunoassays have been addressed by Glick and Winefordner (F21). Pace and Maple (F22) illustrated the analytical merits of laser-induced phosphorescence in the multicomponent determination of halogenated aromatic hydrocarbons. The spectrometric measurement is preceded by sample preparation in low-temperature, vapor-deposited parent molecule matrices. A minimum detectable quantity of about 0.8 pg for 1,4-dichloronaphthalene is reported. Simultaneous oxidase enzymatic and chemiluminescence reactions carried out by use of hexadecyltrimethylammonium bromide in a reversed micellar system has been shown to enhance the determination of amino acids and glucose (F23). A chemiluminescence detector for sulfur-containingspecies in supercritical fluid chromatography based on the gas-phase reaction between fluorine and organosulfur com ounds has been proposed by Bornhop et al. (F24). Since the &orescence emission of pyrene overlaps that of its inclusion complexes with cyclodextrins, Nelson et al. (F25) made use of time-resolved emission spectroscopy in a study of such complexes. The enhancement of fluorescence lifetimes and increase in formation constant values by alcohols are reported. Table I1 com iles additional selected determinations based on chemi- and gioluminescence. An increased interest in the determinations of inorganic species and in continuous-flow sample/reagent(s) processing can be observed.

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T a b l e 11. Selected Determinations Based on Chemi- a n d Bioluminescence determined species

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determination of pg/mL concentrations. Continuous-flow system based on the luminol chemiluminescence trigered by Br, generation: Hz02 BrO< Br- in acidic medium determination in water samples based on enhanced luminol chemiluminescence. Continuous-flow system with in-line membrane separation (microporous PTFE tube) to eliminate metallic interferences. Determination time: 3 min/sample; limit of detection: about 0.04 F/mL free chlorine in aqueous systems determined by the chemiluminescence of the reaction between hypochlorite and lophine. Limit of detection about 75 pg/L as C1,. Flow injection system with gas diffusion membrane determination in tap water. Continuous-flow system using xanthene dye ClZ chemiluminescence continuous-flow method using chemiluminescence from the reaction of Cr(V1) 2,4,5-triphenylimidazolewith H202in basic medium. Limit of detection 20 ng/mL. Determination in water samples. Chromium(V1) is separated from interfering ions (e.g., Cu(I1) and Cr(II1)) with activated alumina chemiluminescence of Cu(II), CN-, and dissolved O2 enhanced by using uranine in a Cu(I1) and free CN80% 2-propanol-20% water medium. Mechanism of chemiluminescence discussed. Application to the analysis of tap and river water samples as well as tomato leaves electrochemiluminescence of luminol. Determination at subnanomole level. H2Oz Continuous-flow processing lead intensification of the luminescence produced in the reaction between H 2 0 2and Pb(I1) 4-diethylaminonaphthal hydrazide. Limit of detection: 0.02 ng/mL. Determination in spiked tap water. Kinetics of the reaction discussed luminol chemiluminescence in basic medium. Limit of detection: 5 X IO4 M NO< luminescence quenching of the tris(4,7-diphenyl-l,l0-phenanthroline)ruthenium(II) 0, (dissolved and in the gas phase) perchlorate immobilized on a silicone rubber. Quenching quantitated either by lifetime or intensity measurement. chemiluminescence from reaction with indigo-5,5’-disulfonate. Linear concentration 03 (as) range: 0.025-410 ng/mL. Limit of detection: 0.006 ng/mL. Mechanism of chemiluminescence discussed selective determination based on the chemiluminescence of the reaction between S27,7,8,8-tetracyanoquinodimethaneand S2- sensitized by Rhodamine B in alkaline medium containing dioctadecylmethylammonium chloride bilayer membrane aggregates in acetonitrile. Minimum detectable auantitv: 0.05 ng. - Continuous-flow s;&em (240 injections/h) chemiluminescence of Ce(1V) in a continuous-flow system. Sulfite determination in SOz(g) and sulfite ions the 0.3-3 pg/mL range. Emission enhanced with 3-cyclohexylaminopropanesulfonic acid. Method applied to determination of SOz(g) in air luminol-H202 chemiluminescence (pH 7.5-8.5). Determination at the fraction of aliphatic peroxy acids Fg/mL level based on the measurement of maximum luminescence signal M level using coimmobilized (on bioluminescence measurement at the glucose-6-phosphate, glucose-I-phosphate, BrCN-agarose) multienzyme preparations (bacterial luciferase, NADsH2:FMN oxidized nicotinamide adenine nucleotide oxidoreductase, glucose-I-phosphate dehydrogenase, and phosphoglucomutase) Br-

+

G. KINETIC METHODS BASED ON UNCATALYZED REACTIONS The Koenig reaction used in the determination of low concentrations of pyridine. is based on breaking down p idine (e.g., with cyanogen bromide and phosphorus trichlor& and coupling the glutaconic aldehyde derivative formed with an aromatic amine to form a polymeric dye. Cassasa.9 et al. ( G I ) have shown that a kinetic (initial rate) approach to measurement and the use of 4,4’-diaminostilbene-2,2’-disulfonic acid as coupling agent removes disadvantages observed with equilibrium-based measurements. Kinetics of the now classical Jaff6 reaction for creatinine determination has received attention b several research groups in the past and seems to be periockally revisited. Two recent reports of this kind concern analytical implications (G2)and application to the kinetic determination of creatinine in human serum (G3). Both include chemometric evaluations. A kinetic determination based on the direct dependence of the length of an induction period and As(II1) concentration in the periodate-bromide reaction has been pro osed by Alekseeva and Kurtova (G4). The induction periozappears + 2Br- + 2H+ = Br2 + IO3because the direct reaction (IO4+ H20). does not. take place until the As(II1) is consumed in + As02- = IO3-+ AsO,-). Rethe periodate oxidation (IO4action rate detection was accomplished amperometricallyand a limit of detection of 0.03 pg/mL is reported for As(II1). Using a fluoride-selective electrode for potentiometric reaction rate monitoring, Athanasiou-Malaki and Koupparis (G5) study the kinetics of some hydrazines, isoniazid, and The sodium azide reactions with l-fluoro-2,4-dinitrobenzene. 454R

ANALYTICAL CHEMISTRY, VOL. 62, NO. 12. JUNE 15, 1990

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F31 F32 F33 F34 F35 F36 F37

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information collected was used to develo initial rate and fixed-time determination of these species. xpplication to the determination of hydrazine hydrochloride, procarbazine hydrochloride, isoniazid, and rimactazid in harmaceutical tablets o r capsules is reported. The same autiors studied the effect of various surfactant species on the reaction of 1fluoro-2,4-dinitrobenzenewith amino compounds also using a fluoride ion selective electrode for reaction rate monitoring (G6). They concluded that satisfactory micellar-catalyzed determinations of cephalexin, sulphamethizole, and cetyltrimethylammonium bromide in pharmaceutical preparations can be performed. Sucrose in the presence of other carbohydrates in the 0.014.10 M range was determined by a fixdetermied-time procedure (30-min hydrolysis time) (0, nation being based on the monitoring, with a periodate-selective electrode, of the reaction between periodate and the monwccharides produced in the hydrolysis. The method was ap lied to analysis of milk products and soft drinks. !he reaction between ascorbic acid and Mn(CN)5N02-in basic medium has been used in conjunction with the method of tangents for the determination of ascorbic acid at 4 x lo4 to 6 X M levels (G8). The method was applied to the determination of ascorbic acid in pharmaceutical sam les and or? and lemon juices. The kinetics of the reaction getween has been studied Tc( 11) and 1,3,5-triphenyl-A2-pyrazoline by Grases et al. (G9).Technetium can be determined by a rate method in the 0.01-1.2 mgL-’ range. The reaction of vanadate ion with 1,8-diamino-4,5-dihydroxyanthra uinone-2,7-disulfonic acid has been used to determine vana\ium (2.5-50 pg mL) by spectrophotometric monitoring and use of the met od of tangents (GIO). De-

i,


termination of nonvolatile V(V) in two crude oil samples is illustrated and the results are com ared with those obtained by applying the ASTM method. 8yanide concentrations in the 0.1-1.3 mg/L range have been determined by spectrophotometric monitorin (348 nm) of the redox reaction between CN- and Mn(CN7 NO< ions ( C I I ) . Large amounts of SCN- can be tolerated. $h'e method was a plied to the determination of cyanide in commercial KS N reagent. Propanolol, a fl-adrenergic blocking agent, has been determined in drug formulations by a fixed-time procedure (CI2). Oxidation of propanol01 by dichromate at 90 "C in 5 M sulfuric acid, reaction quenchin after 20 min reaction, and absorbance measurement of Cr(III$at 590 nm were used. The determination of tantalum in the presence of niobium exloiting differences in rates in a li and exchange reaction has !,en pro osed by Yamada et al. (bI3). Determination at the 10-s-10 M level was accomplished using 4-(2-pyridylazo)resorcinol and oxalate, tartrate, citrate, or nitrilotriacetate as com eting ligand. A logarithmic extrapolation approach was u s e f for the determination of tantalum. Stopped-flow mixing has been frequently used in rate determinations based on uncatalyzed reactions. Phosphate concentrations in the range of 5 rg/L to 1 mg/L have been determined by a fixed-time procedure using stopped-flow mixing by Kana a and Hiromi ( G I 4 ) . The method is based on monitoring t e color formation of the ion pair between 12-mol bdophosphate and Malachite Green. Determination of t o t s phosphate in a variety of food products (noodles, vinegar, yogurt, butter, honey, mayonnaise, and ketchup) is illustrated. The same authors reported a combination of solvent extraction (for preconcentration urposes) and stopped-flow kinetic monitoring of 12-molyb8ophosphate for the determination of orthophosphate at sub-microgram per liter concentrations (CIS). Extraction is into isobutyl alcohol and reduction effected with stannous chloride. The stopped-flow measurement requires only half a second; sample preparation for measurement requires, however, about 1 h. The formation of a 1:l compound between the oxidation roduct of theophylline and Ce(IV), the-oxidant, was followed Euorometrically after stopped-flow mixing and has been used for the determination of theophiline in commercial pharmaceutical tablets and solutions ( C I 6 ) . Campi and Ingle ( G I q determined aluminum by following the rate of formation of its complex with 2,4,2'-trihydroxyazobenzene-5'-sulfonic acid. The fluorescence of the complex was used for monitoring; a limit of detection of 0.1 ng/mL is reported. The procedure was applied to the determination of aluminum in standard spinach leaves and river water. Carbaryl and its hydrolysis products and mixtures of them have been determined by a method based on the rate of couplin with 1-naphthol and diazotized sulfanilic acid (GI8). Stoppedi-flow mixing and spectrophotometric monitoring was used. Simultaneous determination made use of initial rates measured under different experimental conditions. PBrez Bendito et al. (CI9) determined uric acid in serum and urine using stopped-flow mixing and fluorometric monitorin of the reaction between allantoin and N(CH,)C(NH )-C!(CN)2. Allantoin forms in the reaction of the uric acid with H202 (basic medium) present as a coreagent. The linear range for determination is 0.08-3.00 mg/L and the extra olated limit of detection is 0.03 mg/L. Reactions are Carrie out at 40 "C and calibration graphs pre ared plotting initial rates versus uric acid concentration. earmona et al. (C20) used stopped-flow mixing to determine acetaminophen by spectrophotometrically following the formation of tris[l,lOphenanthroline]iron(II) at 510 nm resulting from acetaminophen oxidation by tris[ l,l0-phenanthroline]iron(III). The approach was applied to the analysis of pharmaceutical samples for their acetaminophen content. Hydrolysis of carbofuran yields carbofuran phenol and this product when reacted with diazotized sulfanhc acid forms a chemical species absorbing photons a t 470 nm. Following the rate of color formation after stopped-flow mixing allows determination of carbofuran in the 1-40 pg mL range (C21). Carbofuran in soils was determined by t is approach. Employing stopped-flow mixing and photometric monitoring, Gutierrez et al. (G22) determined butylated hydroxyanisole in commercial oil samples (sunflower, corn, and olive oil). Initial-rate and fixed-time approaches were used with about the same analytical figures of merit found for either

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approach. Micrograms er milliliter concentrations of Lcysteine were determinedy! using stopped flow and following the analyte oxidation by 2,6-dichloroindophenolin a slightly alkaline medium (G23). As many as 80 samples per hour can be processed by the proposed method, which is rather selective for L-cysteine. Twenty four primary and secondary amines were determined by using a fluoride-selective electrode to monitor the amine reaction with l-fluoro-2,4-dinitrobenzene(G24). Initial-rate and fixed-time a roaches were used for determinations in the 10-3-104 g r a n g e . Bromate in bread was determined by an initial rate approach based on the reaction with di-2-pyridyl ketone 2-quinolylhydrazone ((225). The reaction produces a colored and fluorescent product that can be used for reaction monitoring. Determination in bread is better performed with spectrophotometric monitoring and after sample preparation involving freeze-drying under vacuum for 48 h and aqueous extraction.

H. DIFFERENTIAL RATE METHODS As with rate determinations using uncatalyzed reactions, differential rate determinations in the past 2 years have been sustained by an im etus provided b stopped-flow mixing. Gutierrez et al. (HIPhave used initidrate measurements to simultaneously determine phenylhydrazine and hydrazine. Stopped-flow mixing and monitoring of the absorbance of the product of the reaction with p-(dimethylamino)benzaldehyde was used. Since the products exhibit different wavelengths for maximum absorption, detection was conveniently performed with a diode-array spectrophotometricunit. The same authors applied the method of proportional equations to resolve mixtures of histidine and 1-methylhistidine (H2). They used stopped-flow and fluorometric detection with initial rate and fluorescence amplitude measurements as discriminating variables. Also the same authors reported the simultaneous determination of spermine and spermidine (H3)using stopped-flow mixing and spectrophotometric detection (490 nm) of the colored roduct formed in the reaction of the amines with 1,2-napht!mquinone-4-sulfonate. Initial-rate measurements and the absorbance when the system is at equilibrium permitted formulation of the differential treatment of data. Mixtures in the 20:l to 1:20 ratio range were successfully analyzed at the microgram per milliliter level. The simultaneous determination of 1-and 2-naphthols by rate measurements at different times of reaction (5 s for 1-naphthol, more than 80 s for 2-naphthol) has been reported (H4). Stoppedflow mixing and spectrophotometric monitorin of the colored product of the coupling reaction with diazotize8 sulfanilic acid were used. Optimum times for measurements were derived by error analysis. The fast oxidation of paracetamol and oxyphenbutazone by tris[2,2'-bi yridineliron(I1) in acid medium has been used for the indivixual drugs as well as simultaneous (differential rate) determination of these analgesics (H5). Stopped-flow mixin and spectrophotometric monitoring was applied again here. %his differential determination made use of a modified linear graphical approach roposed by Worthington and Pardue (H6). Kuroda et al. (h7)have implemented open-loop and closed-loop continuous-flowsystems for the simultaneous determination of Fe(II1) and total iron in aqueous solutions. The rate of Fe(I1) oxidation (by dissolved oxygen) accelerated by UV radiation and the formation of a colored complex between Fe(II1) and Tiron (the disodium salt of 1,2-dihydroxybenzene-3,5-disulfonate)are used to discriminate from Fe(II1) to total iron. Quintero et al. (H8) have described a simultaneous determination of propoxur and carbofuran in mixtures using linear graphical extrapolation (H9). A study on the kinetics of complexation of cobalt(I1) b by Arias et 3-(1H-1,2,4-triazol1-3-azo)toluene-2,6-diamine (HIO) led to the dYevelopment of a differential reaction rate method for the determination of Cu(I1)-Co(II1) and Co(111)-Ni(I1) in mixtures. The single-point method based on empirical calibration curves was used and the method was applied to the analysis of hydrofining catalysts and steels. Loripillo et al. ( H I I ) have proposed an interpolation method applicable to the resolution of binary mixtures in which synergistic effects are in operation. The approach is based on a graphical interpolation proposed some years ago (HI2). The feasibility and difficulties encountered in implementing

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differential rate determinations based on competin processes have been addressed by Cummings and Pardue (fiI3). The reactions of methem lobin with cyanide and hemoglobin with hexacyanoferrate(I1f serve as examples since they show opposite directions of signal change with time at 630 nm, the wavelength usually used to monitor the reactions. Fluorescence monitoring of thiochrome resulting from oxidation of thiamine and its pyrophosphate ester by merc.ury(I1) for the dlfferential rate has been used by Gonzalez et al. (H14) determination of the parents compounds. Logarithmic extrapolation was used to determine mixtures in the range 4:l to 1:15 of thiamine to pyrophosphate ester. The method was ap lied to the analysis of synthetic multivitamin samples. The ingvidual determination of the pyrophosphate ester in commercial pharmaceutical samples is also reported. Wentzell et al. (H15) use the linear K h a n filter to analyze differential kinetic data and re ort the advantages of its use. The reaction of amino acids wit 2,4,6-trinitrobenzenesulfonic acid was used to illustrate the point.

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I. KINETICS I N SOME SEPARATION PROCESSES Field-flow fractionation, a chromatography ty e of separation a proach, is now well established as an anJytical tool. has illustrated a dynamic theory of field-flow Davis fractionation in annular channels. River- and Cooper (12) reported on several kinetic aspects of ion exchange at a macroporous strong-base resin (DOWEX MSA-1) for gold, silver, zinc, and copper cyano complexes. Significantly different diffusion behaviors among the tested metals was indicated from the values of the kinetic parameters calculated with the aid of a mathematical model applied to the experimental data. Another mathematical model, for the time-dependent behavior in countercurrent extraction, has been presented by Wilson (13). The model leads to the conclusion that the effluent organic phase approaches steady-state concentration faster than the effluent aqueous phase. The rates of ultrasonic extraction of adsorbed, residual, and total strontium into aqueous solutions and from river sedimenta have been studied by Ackay et al. (14). Flame atomic absorption was used for strontium determination and recoveries from a certified reference material (pond sediment) are reported. The bulk of publications in the past 2 years dealing with kinetics in separations resides in studies on solvent extraction. Fast mass transfer kinetics in solvent extraction has received the attention of Amankwa and Cantwell (15)with a detailed discussion on instrument band-broadening effects. Kim and Tondre (16) have manipulated the rate of complexation of Ni(I1) and Co(I1) ions by effecting a microemulsion environment with a cationic surfadant and Kelex 100 as extractant. Coulombic repulsions result in the need of only 2 min for Co(I1) extraction but 1.5 h for the extraction of Ni(I1). uently, these ions can be kinetically septyated. Kinetics of Pd( ) extraction with o-xylene bis(diethy1dithiocarbamate) or dithizone from aqueous solutions of low chloride concentration and into chloroform have been reported by Ohashi et al. (17). Implications of the separation of Pd(I1) for analytical purposes are considered in the paper. Kokusen et al. (18) discussed the kinetics and mechanism of Ni(I1) and Co(I1) extraction by 5-(octyloxymethyl)-&quinolinol into chloroform. On the basis of differences in extraction rates the authors proposed a kinetic separation of the two ions. The use of 1,lO-phenanthroline modifies the rates of Co(I1) and WIT) extraction with dithizone. It masks the nickel extraction but promotes the extraction of cobalt and thus allows rate-controlled separation (19). Pyridine bases promote the extraction of Co(I1) and Ni(I1) with dithizone (110). 4-Methylpyridine was found to exert a pronounced effect but 3-methylisoquinoline and pyridine a lesser one. The extent of promotion parallels the basicity of the heteroc cles tested. Inaba and Sekine (111)have usedYthermodynamic (equilibrium) information to explain different aspects of the rate of solvent extraction of iron(II1) with trifluoroacetylacetone into carbon tetrachloride. The resence of lipophilic amines or quaternary ammonium salts enfiances the rate of Pd(I1) extraction from hydrochloric acid solutions into dialkyl sulfides. The transient formation

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of ion pairs between the protonated amino or quaternary ammonium salt and PdC1,2- or PdC1, is considered to be responsible for the enhanced extraction (112). The species present in the organic phase is Pd(R2S)2C12,R2S being the dialkyl sulfide extractant; the enhancement can then be considered as a catalytic effect. The catalytic effect of tetrahe tylammonium chloride, thiourea, thiocyanate, and iodide on t i e extraction of Pt(I1) with diphenylthiourea into chloroform was reported in a study of the kinetics of the extraction process (113). Cantwell and Freiser (114)studied the kinetics of ion-pair extraction of tetrabutylammonium picrate from the aqueous phase and into chloroform. Kinetic control of the extraction sequence of lanthanide complexes with ion0 hores has been reported by Chan et al. (115). Significant differences in the rate of extraction ofkhter and heavier lanthanides were found in studies involving mixtures of La and Yb or La and Eu at pH 7.5 and using as extractant theonykrifluoroacetone (3.3 X lo4 M) in benzene. The ionizable macrocyclic ligand used was 1,7-diaza-4,10,13trioxacyclopentadece-N,"-diacetic acid. The same authors revisited the same extraction system using chloroform as or anic solvent this time (116). For binary species involving on! thenoyltrifluoroacetone as ligand, the rate of extraction is Jictated by the rate of dissociation of the macrocyclic complexes in the aqueous phase in relatively slow processes. For mixed-ligand complexes rates are high and independent of dissociation in the aqueous phase. The effect of chloride concentration (in aqueous solution) on the rate of zinc extraction by trilaurylammonium chloride into toluene was studied by Aparicio et al. (117). Increasing chloride concentration results in an increase in extraction rate. The rate of extraction of Cr(II1) from aqueous solutions (as its complex with acetylacetone) and into carbon tetrachloride has been reported (118). The data are interpreted to indicate as rate determining step the 1:l complex formation in the aqueous phase. Several observations on the effect of tubing configuration (e.g., straight or coiled) on solvent extraction in flow in'ection systems have been analyzed by Lucy and Cantwell (1193. The focus of their contribution is a detailed consideration of the role played by secondary flow phenomena in the extraction process. The same authors also addressed in depth si nal broadening in the same approach to solvent extraction $20).

J. MISCELLANEOUS KINETIC ASPECTS OF ANALYTICAL INTEREST The rate of protein-protein interaction in solution of the type encountered in immunoassays can be conveniently monitored with a piezoelectric sensor coated on one of its sides with protein (J1).The feasibilit of a kinetic approach for the determination of immunogrobulins usin centrifugal mixing and turbidimetric monitoring has been femonstrated by Skoug and Pardue (J2). Differences in the kinetic characteristics of the antigen-antibody reaction make it possible to evaluate re 'ons of excess antibody as well as excess antigen and re ions orequivalence. Carlson et al. (J3)have also used centri ugal mixing and analysis of the "absorbance" versus time of turbidimetric measurements to determine recombinant human tissue-type plasminogen activator. Several theoretical considerations on the application of head-space chromatography to the investigation of reaction kinetics in solution have been discussed by Marinichev and Ioffe (54). The equilibrium constant for Q+Y-(organic phase) + X-(aq) + Q+X-(organic phase)+ Y-(aq)

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is termed the selectivity constant for the pair of ions X- and Y-. A kinetic approach to the determination of this t e of constants (in the context of phase transfer catalysis) hasyeen proposed (J5). The approach and values listed in this publication are of interest in solvent extraction and liquid-liquid chromatography. Souaya and Iskander (J6)reported on the kinetics of metal exchange between Cu(I1) and the europium(I1) complex with ethylene glycol bis(Zaminoethy1 ether) tetraacetate, a exchange reaction of interest in differential reaction rate methods and liquid chromatography. A novel application of continuous-flow processing was presented by


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Caiiete et al. (J7).A detailed stud of the kinetics of ion-pair extraction of tris[l,l@phenanthro ineIiron(I1) cation with 23 anionic counterions is presented with analytical implications regarding the individual and simultaneous kinetic determinations of the anions. Paraquat in the (1-27) X lob M levels has been determined by following the rate of its photoreduction in the presence of EDTA and Acridine yellow as sensitizer (J8).The rate was polarographically monitored by following the limiting current of p-benzoquinone produced during the photochemical reaction. Application to the determination of paraquat in herbicides, waters, flowers, spiked soil, and blood sera is reported. Improved selectivity in the spectrofluorimetric determination of free and conjugated indole-3-acetic acid has been remrted bv initial rate measurement of indole(a)-Dvrone -formation ( ~ 9 ) : The kinetics of nickel(I1) ion complexation by 8-hydroxyauinoline in aaueous solutions of DH 4.6-5.4 and in the tem6erature range 15-50 OC has been reported by Li and Smith (JlO).The rates are first order with respect to nickel ion and reversed first order with respect to hydrogen ion concentration. The rates were foIlowed spectrophotometrically after stoped-flow mixin Uskg the same approach, Boumezioud and Fondre studief the kinetics and mechanism of the same reaction but in basic aqueous solutions (JII). The determination of SO2in air by measurement of the time required to decolorize paper strips of equal length impregnated with iodine starch has been proposed by Petrishcheva et al. (J12). It is of interest to note that the same basic approach was used in 1885 by C. Wtiz and F. Osmond for a semiquantitative determination of vanadium, exploiting its catalytic effect on the formation of aniline black from mixtures of chlorate and aniline (J13). The rate coefficients for the and HSO - in aqueous soreaction between NO and S032lutions of pH 5.3-13.0iave been determined by Clifton et al. (J14). The results and mechanistic interpretations by the authors point to the formation of a long-lived ihtermediate when a large concentration of SO 2- is resent. This intermediate may play a role in luminol%~asec!NO~ detectors since it can react with luminol and lead to chemiluminescence. Methods using continuous flow for sample/reagent(s) transport and manipulation are inherently kinetic in nature. The increasin use of such methods increases the importance of understaniin flow phenomena in such situations. To improve this un erstanding, Sioda and Curran (J15)have anal zed the effect of the parabolic flow velocity distribution resu ting from laminar flow. Their paper addresses the influence of the radial position of a given fluid element and the effect of distribution of mass transfer. The authors hope that the model advanced by them “will help to unite...various flow analytical techniques, each of which is independent on the basic physical law of parabolic flow velocity distribution in a circular tube”. Since the effect of the kinetics of chemical reactions on the response si nal obtained in flow injection systems was f i t demonstrad (J16),a few contributions have appeared devoting atbntion to this fact. Recently Van Veen et al. (JI7) have discussed the optimization criteria for a singlebead-string reador in a flow injection system processing chemical s ecies reacting in a consecutive (series) reaction pattern. T e dynamic processes in unsegmented continuous flow (physical and chemical) combine to produce the dispersion that characterizes the shape of the transient peaks in flow-injection procedures. Brooks et al. (J18)have applied moment analysis (second moment) to describe peak shape and dispersion in a single-line manifold. They used an exponentially modified Gaussian model. Rate measurements for reactions occurring on the millisecond time scale by addition of one of the reactants at a constant rate to the species to be determined have been proposed by Marquez et al. (J19). Determination of chlorine and oxchlorine species by flow injection analysis depending on inetic considerations has been described by Gordon et al. (520). Their pa er is of interest with regard to water disinfection and in t i e li ht of analytical requirements imposed by the Safe Water %rinking Act of 1986. Bostros and Huber (J21)have studied the kinetics of the electrochemical oxidation of three- and four-carbon alcohols, glycols, and glycerol at a nickel electrode. Correlation between the rate coefficient for heterogeneous anodic reactions and the inductive substituent constants is presented. 1,3-

.

i

7

R

f

Propanedial can be determined with a limit of detection of 0.2 pM and relative standard deviations (for six replicates) of about 1.5%. Ruslin and Miaw (J22) used a kinetic approach to estimate the formal standard redox potential ( E O ’ ) for a series of polychlorinated and polybrominated biphenyls in N,N-dimethylformamide. Eo’ was estimated from the change in Gibbs free energy for the reaction between the halobiphenyl species and an electrochemically generated reducing agent. Values of the free energy change were extracted from the equilibrium constant for electron transfer, which in turn was estimated from rate coefficients of electron transfer. Uncertainties in values of Eo’ are reported as f0.05 V. Amatore, Wightman, and co-workers have extended their studies on electrochemical kinetics at microelectrodes (J23). Their recent contribution aims at the understanding of voltammograms obtained at low ionic strength by discussion of migrational effects on steady-state or quasi-steady-state voltammograms. Carrier-containing liquid membranes are of interest, for instance, in ion-selectiveelectrode develo ment. Yoshida and and Pb2+transfer Watanabe (J24)have studied the rate of by neutral macrocyclic carriers such as dibenzo-18-crown-6, dicyclohexano-18-crown-6,18-crown-6,and polynactin with a membrane system. The process is diffusion limited and the rate of ion transport depends on the extractability of the metal ion itself. Deviations from equilibrium conditions ex lain the decrease in ion selectivity of ion-selective electrodes Eased on neutral carriers (525). The kinetics of sodium ion complexation by 18-crown-6of interest in ion-selective electrodes and membrane separations have been studied by Hase et al. (J26) who report on the reaction path and the rate coefficients for the reaction. Wunsch and Seubert (J27)have addressed certain kinetic aspects of the Karl Fischer reaction in methanol. Their exrimental observations confiim previous studies on the topic. he Berthelot reaction is extensively used for the determination of ammonia; Harfmann and Crouch (J28)have studied in detail the kinetics of this reaction and clarified several aspects of its mechanistic operation. Several analytical procedures are based on the oxidation of 2,6-dichloroindophenol. Stopped-flow mixing and spectro hotometric monitoring have been employed by Konidari an8Karayannis (J29) to follow the reaction of this species with dithionites, a potential interference in analytical procedures based on such oxidation. The paper reports on the kinetics and mechanism of the reaction. Micellar catal is by dodecyltrimethylammonium bromide in the Sandell-Gthoff reaction Ce(IV)-As(II1)-iodide] was reported by Rubio and PBrez Ben ito (J30).Analytical aspects of micellar catalysis to improve rate determinations are also discussed. Parry and Harris (J31) modified a olycrystalline silicon attenuated total reflection (ATR) suistrate by controlled oxidation to coat it with a silicon diode layer. This layer was used as a model interface to study chemical modification of silica or glans by ATR-FT-IR spectrometry. Part of the studies focused on the kinetics of silane binding to the model surface. The slow reaction with diphenylchlorosilane was monitored by following absorbance changes with time at 2175 cm-’ (Si-H stretching), 2137 cm-’ (Si-H absorption), and 3070 cm-’ (C-H vibrations). Time-resolved signals have been used to uncover errors involved in the direct determination of traces of Cd, Co, Cr, Ni, T1, and Pb in urine by nonflame atomic absorption (J32). Contrary to other claims, the authors conclude that peak height should be preferred to area measurement. Time-resolved laser fluorometric detection has been applied by Kawabata et al. (J33) to detection of proteins after high-performance liquid chromatography. The minimum amount of bovine serum albumin that can be detected is reported as 2.3 pmol. 1-Anilino-8-naphthalenesulfonatewas used as fluorescence probe. Laserna et al. (J34)have shown that the simultaneous (but independent) use of constant-energy synchronous luminescence spectrometry (CESL) and time-resolved phosphorimetry (TRP), although a more complicated technique to apply, may result in improved spectral selectivity. The authors recommend, however, that the analytical chemist try f i t CESL and then TRP, before attempting the combination approach. Reporting on the effect of temperature on the luminescence

8.

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6


45713


properties of benzo[flquinoline adsorbed on filter paper, Ramasami and Hurturbise (535)analyzed in some detail the role of rate coefficients for phosphorescence and for the radiationless transition from the triplet state. An area of increasing interest is the mathematical treatment of data mainly to improve reliability of the extracted information from rate measurements. Using a first-order kinetic model, Pardue and McNulty (536)demonstrated the usefulness of a predictive value approach to evaluate the kinetic response of an ion-selective electrode. This approach can be used for the determination of ammonia using an ammoniaselective electrode. A very useful statistical analysis of exponential-like deca data observed in luminescence and kinetic experiments has teen authored by Marshall (J37). Both single-ex nential and multiex onential data are considered. A criticaEvaluation of extenxed Kalman filtering to compensate for within-run temperature changes in kinetic determinations has been provided by Corcoran and Rutan (J38). The same authors proposed earlier a Kalman-filter-based approach for estimation of kinetic parameters without a precise control of temperature (539). The approach was evaluated with computer-generated data and with experimental data from the reaction between lycine and ninhydrin. Rutan et al. (J40)compared the extenfed Kalman filter and Marquardt’s gradient expansion algorithms for nonlinear least squares. Neither algorithm has advantage for the detection of model errors; the Kalman filter, however, overestimates zero-order rate coefficients substantially more than the Marquardt algorithm. A new algorithm for multipoint calculation of reaction orders, rate coefficients, and initial and final values of the measured signal has been proposed (J41). Although the results are less rehable than those obtained from nonlinear curve-fitting methods, the proposed algorithm can be used with reaction orders close or equal to one where the nonlinear approach fails. The same authors also presented a new algorithm for error-compensated kinetic determinations not requiring prior knowledge of reaction order or rate coefficients (J42). Initial-rate, two-point, fixed-time rate measurement at t = l/k (k = first-order or pseudo-first-order rate coefficient) and multipoint curve fitting methods of data handling have been com ared by Bacon and Pardue (J43).The comparison was appied to the JaffB reaction for creatinine determination. Good precision and linearit was observed with all the compared approaches. The autgors conclude, however, that application of the multipoint curve fittin predictive method should otentially result in improved refiability. Thomas et al. (J447compared integration of rate data with fixed-time (single point) kinetic determinations. It is decided that enhancement of s -to-noise ratios is affordable by integration. According to lskens et al. (J45),application of Simplex optimization in the estimation of rate coefficients from concentration versus time curves may result in unreliable information. A practical case is briefly discussed to illustrate the point. Interest in extending the linear range of calibration plots beyond the Michaelis-Menten constant value in substrate determinations based on enzyme-catalyzed reactions has received some attention in the past years. Lunding et al. (5461, for instance, have proposed lots of (IR),m - (IRIblank,with IR = initial rate, versus [ ( d ) - (IRlb k]/[s] to extract values of the apparent rate coe!!$ient for #e catalyzed path, k , and the Michaelis-Menten constant, K . Then lots of -!IR)p,k]/(kd yersus [SI/(< +?SI) can e! used as call ration p ots with linearity considPerably extended beyond [SI = K,. Hwang et al. (J47)described the use of competitive spectrophotometry to obtain rate coefficients for enzyme-catalyzed reactions. They introduced an equation describing the action of an enzyme on a substrate in the presence of another substrate. The equation can be transformed to give linear plots from which the maximum initial rate and the Michaelis-Menten constant can be extracted for the second substrate. A mathematical treatment of eneral interest in the timeresolved spectrofluorometric fetermination of inorganic s ecies was given by Berthoud et al. (548). A family of calitration graphs measured at different times through the atomization step in a graphite furnace has been proposed by Leyon and Holcombe (549)to extract analytical information even at high analyte concentration. The data ensemble is

P

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458R


obtained from the falling portion of the ical transient signal away from the peak value. The approac circumvents problems of nonlinearity in calibration curves resulting from self-absorption and facilitates calibration without the need for time-consuming dilutions. It also minimizes instrumental adjustments. Extrapolation of a first-order vaporization-rate expression permits direct determination of chemical species in metallurgical samples by electrothermal atomic absorption spectrometry (J50). The approach is illustrated with the determination of lead in different samples (tin, copper, and steel). Rate coefficients of atomization, ionization, recombination, and vapor plume ex ansion in an inductively coupled plasma have been estimate: from the zeroth and first moments of the resulting transient signal (J51). Sunner et al. (J52)used a gas-phase kinetic scheme to model experimental data of the fast atom bombardment mass spectra of glycerol and diethanolamine mixtures. In the past it had been customar to review publications that described instrumentation anlcomputer systems that were not specifically for analytical kinetic uses. As this literature has become so extensive and is comprehensively reviewed elsewhere, it has been decided to omit this section from this year’s review.

tyR

ACKNOWLEDGMENT D. PBrez-Bendito gratefully acknowledges research support from the Spanish Government in the compilation of this review. LITERATURE CITED GENERAL, BOOKS, AND REVIEWS (1) Mottola, H. A.; P6rezSendYo. D.; Mark, H. B., Jr. Anal. Chem. 1988, 60, 181R-200R. (2) P6rez&ndYo, D.; Silva, M. Klmtlc Methods in AnaEyrical Chemistry; Ellis Horwood: Chichester, 1988. (3) Vinjamoori, D. V. In Ouantitative Trace Ana&& of Bidogical Materials; McKenzie, H. A., Smythe, L. E., Eds.; Elsevier: Amsterdam, 1988, Chapter 17. (4) Tabata, M.; Nakano, S.; Kawashima, T. Bunseki 1988, (9, 347-354. (5) Nakano, S.; Kawashima, T. Bun&/ 1987, (5), 317-324. (6) Kiss. L. Kinetics of Elecirochemlcal Metal DlssoMion; Elsevler/Akademia Kiado: Budapest, 1988. (7) Pokol, 0.; Vahgyi. 0.CRC Crlt. Rev. Anal. Chem. 1988, 79. 65-93. (8) Luque de Castro, M. D.; Valcarcel, M. Trends in Anal, Chem. 1989, 8 . 172- 177. (9) Hlrornl, K.; Karaya, K. Anal. Sci. 1988, 4 , 445-454. (10) P&ez-Bendito, D.; Sllva, M.; Gomez-Hens, A. Trends in Anal. Chem. 1989, 8 , 302-308. (11) Abruiia, H. D. Coord. Chem. Rev. 1988. 86, 135-189. (12) Kamau, G. N. Anal. Chlm. Acta 1988, 207, 1-16. (13) Diemandis, E. P. Clin. B h h e m . 1988. 27, 139-150. (14) AIRhan, H.; Stenman, lJ.-H. Am. Blotech. Lab. 1988, 6(6), 8-13. (15) Krlcka, J. Anal. B h h e m . 1988, 775, 14-21. (16) Grayeski, M. L. Anal. Chem. 1987, 59, 1243A-1256A. (17) Hurturbise, R. J. Anal. Chem. 1989. 61, 889A-895A. (18) Kasa, I. Mgy.Kem. Lapja 1988, 43, 209-218. (19) Pantel, S. Anal. chim. Acta 1987, 799, 1-14. (20) Yatsknirskli, K. 8. Zh. Anal. Khlm. 1987, 42, 1743-1752; J . Anal. Chem. USSR (Engl. Transl.) 1987, 42, 1373-1381. (21) Pantel, S.; Weisr, H. Anal. Chlm. Acta 1987, 202, 1-24. (22) Miller, M. P. Appl. Spectrosc. Rev. 1987, 23, 329-345. A. KINETIC METHODS FOR DETERMINATIONOF CATALYSTS

(Al) Lacy, N.; Christian, G. D.: Ruzlcka, J. Anal. Chim. Acta 1989, 224, 373-381. (A2) Xu, J.; Huang, X.; Fu. 0.; OU, Q. Fenxl Hwxue 1989, 77, 146-148. (A3) Zhang. 2.; Wing, Y.; Zhou, W. Fenxi SMyanshi 1987, 6 . 34-36. (A4) Yarnane, T.; Watanabe, K.: Monoie. H. A. Anal. Chim. Acta 1988, 207, 331-336. (A5) Marc& R. M.; Caluli, M.; Borrull, F.; Cerd. V. Thennochim. Acta 1987, 777, 89-95. (As) Cald, M.; Mar&. R. M.; Homs, N.; Ramirez de la Plscina, P.; Borrull, F. Thermochim. Acta 1988, 730,241-248. (A7) Alekslev. A.; Anplova, M. Mlkrochlm. Acta 1987, 11, 243-247. (A8) Bonull, F.; Cerda, V. Thennochrrm. Acta 1989, 737, 283-268. (A91 Yuan, Y.; Wang, Y.; Qu, K. FenxlHuexue 1989. 77, 65-67. (A10) Chen, G.; Zhang, 2.; Lu, S. Fenxi Shiyanshi 1988, 7 , 12-15. ( A l l ) Fukasawa, T.; Kawakubo, S.; Tan, L. Anawst 1987, 772, 1247-1251. (A121 Smknova, E. 8.; Sbel’tsova, E. D.; Narycheva, I.A.; Dolmanova, I . F. Vestn. Mask. Univ. Ser. 2 : Khlm. 1987, 28, 482-465. (A13) Men, R.; Llu, S.; Du, H. Jilin Daxue Zkan Kexue Xuebao 1987, 7 , 79-83. ._ (A14) Bargallo, I.;Borrull, F.; Cerd, V.; GuasCh, J. 7Mnnochim. Acta 1987, 117, 283-289. (A15) Casassas, E.; Izqulerdo Ridorsa, A.; Pulgnou, L. Talanta 1988. 35, 199-203.

KINETIC ASPECTS (A16) Yuan, Y.; Qu, K. Halyang Yu Huhao 1988, 79, 157-163. (A17) Casassas, E.; Pulgnou, L.; Izqulerdo Ridorsa, A.; Pedrob. M. J . of PhetITMc. & Blamed. Anal. 1988, 6 , 781-786. (A18) Kawakubo, S.; Katsumata, T.; Iwatsuki. M.; Fukasawa. T.; Fukasawa, T. Analyst 1988, 173. 1827-1830. (A19) Ayiannidis, A. K.; Voulgaropoulos, A. N. Analyst 1988. 773, 153-157. (A201 Tanaka. A.: Imasaka, Y.: Hayashi. K.; Deauchi, T. Bunseki Kagaku ’ 1087, 36, 811-814 (A21) OUt6fTez, M. C.; G6mez Hens, A.; P&ez Bendko, D. Analyst 1989, 174, 89-92. (A22) Wang, 2.; Zheng. 2.; Gong, 0. Fenxi Huaxue 1989, 77, 83. (A231 Wang, 2.; Zheng, Z. Haiyang Xuebao 1988. 6 , 249-250. (A24) Bochanova, V. P.; Baralei, N. N.; Zuboya, V. E.; Kleschev, N. F.; Metkubva, I.A.; Morgunova, E. T. Zavod. Lab. 1988, 5 4 , 3-4. (A25) Llu, 2.; Xiao, Y. Yankuang Ceshi 1988. 5 . 193-195. (A26) Bilenko, 0. A.; Mushtakova, S. P. lzv. Vyssh Uchebn Zaved. Khim. T e k h d . 1988, 3 7 , 52-55. (A27) Pbez Ruiz, T.; Martinez Lozano. C.; T o d s Martinez, V.; Baiidn del Valle, J. An. O i h . 1988, 6 4 , 84-88. (A28) Men, R.; Liu, S.; Yu, Y. Fenxl Huaxue 1987, 75, 77-79. (A29) Yang. S.; Tong, H. Huaxue Xuebao 1987, 45, 711-714. (A30) Calull. M.; Marc(. R. M.; Torres, J.; Borrull, F. Thennochim. Acta 1988, 127, 73-79. (A31) Chen, 0.; Huang, Y.; Hu, Y. Fenxi Huaxue 1988. 76, 230-232. (A32) Hirayama, K.; Unohara, N. Anal. Chem. 1988, 60, 2573-2577. (A33) Simeonov, V.; Themelis, D.; Stratis. J. Fresenius 2. Anal. Chem. 1988, 337, 39-41. (A34) Origor’eva, L. A.; Dodin, E. I.; Kazazis, V. M. J . Anal. Chem. USSR (Engl. Transl.) 1987, 42, 1747-1750. (A351 Aleksiev, A.; Stoyanova, A. Anal. Lett. 1988, 2 7 , 1515-1532. (A36) Matat, L. M.; Mlzetskaya. 1. B.; Olelnik, N. D. Zh. Anal. Khim. 1988, d.9 , i m u m n--. R (A37) Cheng, G. Fenxi Huaxue 1987, 75, 920-922. (A38) Beyer, W. F., Jr.; Fridovich, I. Anal. Biochem. 1988, 770, 512-519. (A39) Ushakova, N. M.; Dolmanova, I . F. Vestn. Mosk. Univ. 2 : Khim. 1887. 2 6 . 466-470. (A40) Z i n g , C.; Kawakubo, S.; Fukasawa, T. Anal. Chhn. Acta 1989, 217, 23-30. (A41) Wang, 2.; Zheng, 2.; Hu, X. Fenxi Huaxue 1987, 75, 145-147. (A42) Zhao, H. Huanjing Huaxue 1987, 6 , 76-78. (A43) Kawakubo, S.; Fukasawa, T.; Iwatsuki, M.; Fukasawa. T. J . Flow l n ~ t i o nAnal. 1988, 5 , 14-22. (A441 Wang. 2.; Zheng, 2.; Hu, X. Haiyang Xuebao 1987. 9 , 391-396. (A45) Cheng, D.; Zhao, M.; Li, H.; Liu, C. Lihua Jianyam. Huaxue Fence 1988, 2 4 , 240. (A461 m n g , 2.; Wang, Y.; Hen, L. Fenxl Huaxue 1989, 77, 160-163. (A47) Tarin. P.; Blanco, M. Analyst 1988, 773, 433-436. (A48) Zolotov, Y. A.; Shpigun, L. K.; Koiotyrkina, I.Y.; Novikov, E. A.; Bazanova, 0. V. Anal. Chim. Acta 1987, 200, 21-33. (A49) Kolotyrklna, I. Y.; Shpigun, L. K.; Zolotov, Y. A. Zh. Anal. Khim. 1988, 43, 284-288. (A5O) Calull, M.; Marc(, R. M.; Ram& de ia Piscine, P.; Homs, N.; Torres, J.; Borruli, F. Thermochm. Acta 1988, 725, 319-325. (A51) Yuan, Y.; Wang, Y.; Qu, K. Fensi Huaxue 1988, 76, 315-319. (A52) Zhang, 2.; Li, 8. Fenxi Huaxue 1988, 76, 334-336. (A53) Zhan Z. Huaxue Shli 1989, 7 7 , 4-7. (A54) Hernkdez Her&ndez, F.; Medina Escriche, J.; Ldpez Benet, F. J. Anal& 1988. 16. 523-525. (A55) Fang, G.; Tang, Z. Fenxi Huaxue 1987, 75. 46-49. (A561 Rao. K. M.; Reddy. T. S.; Rao, S. 8. Analyst 1988, 173, 983-985. (A571 Xu, J.; Yang. H. Xiamen Daxue Xuebao Ziran Kexueban 1988, 2 7 , 548-552. (A58) %nchez Pedreiro, C.; Sierra, M. T.; Sierra, M. I.; Sanz, A. Analyst 1988, 113, 145-148. (A59) Yu, 2.; Li, Y. Fenxi Huaxue 1987, 75, 841-843. (A60) Pessenda, L. C. R.; Jacintho, A. 0.; Zagatto. E. A. G. Anal. Chim. Acta 1988, 214, 239-245. (A61) Manchobas, R. M.; Slat, A.; Borrull, F.; Ramirez de la Piscina, P.; Homs, N. Themmhim. Acta 1989, 742, 107-115. (A62) Borrull, F.; Torres, J.; Cerd, V. Analyst 1987, 772, 1453-1455. (A631 Borruli. F.; Cerd, V. Themmhlm. Acta 1987, 721, 367-372. (A641 He, X.; Cai, Y.; Gong, H.; Hu, Z. Huaxue Tongbao 1988, 70, 41-42. (A65) Mushtakova, S. P.; Kraskova, T. P.; Gumenyuk, A. P.; Romanova, E. A. Zh. Anal. Khim. 1988, 43, 2014-2017. (A66) Svbba Reo. P. V.; Vijayasree, M.; Saradamba, G. V.; Ramakrishna, K. J. Ind&n Chem. Soc. 1988, 6 3 , 743-746. (A67) Kawamura, K.; Igarashi, S.; Yotsuyanagi, T. Chem. Lett. 1987, 7 7 , 2217-2220. (A68) Zhitenko, L. P.;pysev, A. P. Zh. Anal. Khim. 1988, 43, 483-485. (A69) b u U , F.; Ramirez de la Piscine. P.; Homs, N.; Torres, J. W m o chh. Acta 1968, 127, 209-216. (A70) Mart-krez Lorano, C.; Pirez Rulz, T.; T o d s , V.; Abeliin, C. Analyst 1989. 714, 715-717. (A711 Lened. N. B.; Pantaler. R. P. Zh. Anal. Khim. 1988, 43, 452-457. (A72) Zhang. 2.; Zhou, W.; Wen, Y. Gaodeng Xuexiao Huaxue Xuebao 1987, 8 , 407-412. (A73) Jiang, 2.; Liang, A.; Dai, G. Huanjing Kexue 1987, 8 , 703-705. (A74) Dei, 0.; Jlang, Z. Gaodeng Xuexiao Huaxue Xuebao 1987, 8 , 703-705. (A75) Wang, M.; Chen, 0. Fenxl Shlyanshi 1988, 7 , 22-23. (A76) Mlbvanovlc, G. A.; Wheta, M. A.; Vassilios, A. Microchem. J . 1988, 37, 263-267. (A771 Mar&. R. M.; Calull. M.: Torres. J.: Borrull. F. Anaht 1988. 773. ’ 505-508. (A781 thao, H.; Ll, H.; Qlu, 2. FenxlHuexue 1088, 76. 480. (A79) Zhu, Y.; Shao, J. Fenxi Huaxue 1987, 75, 885-869.

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OF ANALYTICAL CHEMISTRY

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DIFFERENTIAL RATE METHODS

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