Some Kinetic Aspects Relevant to Contemporary Analytical Chemistry Horacio A. Mottola Oklahoma State University, Stillwater, OK 74078 In the past few years, kinetics has been finding a place in textbooks in analvtical chemistry (1). The dominance of equilibrium-basedmethodology skems to be diminishing. I t
colorimetric determination of traces of metals ( 3 )have made room in their pages for mention of kinetic determinations. The second edition of the monumental Treatise on Analvtical Chemistry carries a chapter on the application of kmetics and catalysis to analysis (4) and an overview of catalytic methods has found a place in a heterogeneous collection of papers edited in memory of the late Anders Ringhom (5).The concepts which have dominated the textbook, however, are the kinetic methods of determination. Catalytic (including enzymic-based) determinations and the simultaneous determination of more than one species (differential rate methods) have become established as the main areas of kinetic-based analysis. These dominant aspects are reflected in the two monographs published on the suhject (6,7)and in more recent treatments of the suhject in contemporary analytical texthooks (81. , , Granted that analvtical chemistrv . as practiced . today is quite different from that of several years ago. Many times. and even for those involved in the teaching of this everchanging subdiscipline of chemistry, the change centers on instrumental approaches, and fundamental concepts appear overshadowed by the marvels of modern instrumentation. Textbooks. and bv extension courses, seem to emphasize ~~~
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or ignored. Kinetics gets a superficial treatment in most first semesters of- analvtical courses in connection with the erowth of me~~-~~~ ,.
Figure 4. SigmI-type profile (sample injection imo unsegmented flow) identifying S(rn8.x). qrnax), and qbas). [From reference (34with permission from Elsevier Publishing Go.]
iowed between repetitive injections (rate of determination). Thus, an a priori knowledge of the values of rate proportionality constants helps in-method development a i d &timization. Sometimes these constants can be extracted separately, but in some cases the isolation of such consecutive processes is difficult. Direct estimation of the values from signal nrofiles obtained when the consecutive nrocesses are
(51 Yatsirnirskii. K. B.. and Tokhonoua, L. P., in "Essays on Andytical Chemistry" (in Memory of Professor Andem Ringbom), w a d n e n , E. 1Editaii. Pergarno" P m 8 , Oxford. 1977. pp. 529-536. (61 Yatsirnirskii. K. 9 , "Kinetic Msthods of Analysi8.l)Pergsmon Press, Oxford, 1966. (7) Mark, Jr.. H. R.,Rech"itz, G.A..snd Gremke,R. A.,"Ki"efi~ in AndyuedChemisUy:. Wilcy-lnterscience. New Yolk. 1968. (8) Mark. Jr., H. B., in "InsVumentalAnalysis."Bsuu,H. H.,Christian,G.D.. andOIHeiUy (Editors), Allyn and Bacon, Bmion, Massaehusettn. 1978, PP. 628-558. (9) Nielaen. A. E.. "The Kinetics of Precipitation," The Maemillan Ca.. Now York, 1964. (101 Giddings, J . C., '"Dynamics of Chromatography? Part I, 'Principles and Theory: MarcelDekker. NeuYork, 1965. (11) Giddings. J. C., J . CHEM. EDUC.. 44.704(1967). 112) Huher. J. F. K.. in "Comprehensive AnslylicalChemistry~Vol.IIB. Wi1son.C. L.,and Wi1~on.D.W. (Editarsi,AmericanElseuier,NewYork,1968. (l?i Kuger. 8.L., Snyder. L. R., and Horvath. C. (Editmi, "A" 1ntraluCtion toseparation Science." Cheoter3. Wilev-lntersciscrencs. New York. 1973. Zh.,2,44 (1959). im. Acto, 17.761 (19611
~ d .~~h~ , wilpy & sc XI, h c . : ~ e wYork, 196l.~hapto;8:(bi Benson. S. w..''T~; New York. N.Y.. 1960. ChaoLer ~ o u .~. d ~..t of i.m chemical .s. .. ~ i .n2."~McGraw-Hill. t ~
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' 'icoi Chemistry, 2nd Ed.. John Wiloy & Sons, New York. N.Y., 155s. Analysis:
application to the determination of some phenothiazines by means of a transient redox effect in their oxidation by cerium(1V) has been discussed ( 3 4 ) . Conclusions Three rather specific areas of analytical chemistry-chromatography, flameless atomic absorption spectroscopy, and
other techniques or approaches can be scrutinized similarly to expose their kinetic nature. Exposure of students in analytical courses (from undergraduate sophomore to first-year
Bauer. H. H..
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1978.chapter i!I. Peaoh. R. LShields.: L. 0 ,Cairns. T., and MeWillism, I. G., '"Modern Melhods of Chemical Analysis: !2nd.Ed.. John Wiley &Sons. NevYork. N.Y., 1976,Chspter 26. Thiers. R.E.Co1e.R. Fl.,endKirsch, W. J., Clin Chem., 13,451 (19671. walker. w H. c., in " Continuous Flow Analysis: Theory and Practice," Furman, William 9. (Editor), MareelOekker Inc.,New York, N.Y., 1976, Chaptar7. S k e m . JI.. L ~ . , ~ m J. e Pulhol.. r 28, 811 (1957). h a n k , J. and are, IP. E., Camegie lnslitutiono/ Woshingtan, Yeor Book.72.1972,
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