Cf. Hogan et Rj. Forster, Mediated electron transfer for electroanalysis: transport and kinetics in tin films of [Ru (bpy)(2)PVP10] (ClO4)(2), ANALYT CHIM, 396(1), 1999, pp. 13-21
Thin films of the redox polymer, [Ru(bpy)(2)PVP10] (ClO4)(2), deposited on
electrode surfaces are effective mediators for the oxidation of oxalate, bp
y is 2,2'-bipyridyl and PVP is poly-4-vinylpyridine. The effects of systema
tically Varying the electrode rotation rate, the film thickness and the ele
ctrode potential, on the modified electrode rate constant reveal that the c
atalytic current is limited by the kinetics of the cross-reaction and that
the reaction takes place throughout the layer (Lk mechanism). The rate cons
tant for the cross-reaction of the Ru3+ centres with oxalate is 3.1 x 10(2)
M-1 s(-1). Diffusion of the analyte through the layer is relatively unimpe
ded and a value of 3.3 x 10(-6) cm(2) s(-1) is observed for the diffusion c
oefficient. In sulphuric acid electrolyte, charge transport through the fil
m is a diffusion Like process and the charge transport diffusion coefficien
t, D-CT, as measured by both cyclic voltammetry and chronoamperometry is 2
x 10(-11) cm(2) s(-1). This charge transport rate is independent of the con
centration of sulphuric acid as supporting electrolyte indicating an open p
orous layer structure in this medium. The application of the layers for amp
erometric detection of oxalate is demonstrated using a flow injection analy
sis system. A linear response range extending from 2 x 10(-5) to 6 x 10(-3)
M was obtained with a detection limit of 0.35 ppm. The precision of the re
sponse of the system is evaluated (1.53% RDS for 10 repeated injections), a
s is the response time (9.8 s for 98% of the maximum response). The possibi
lity of using the layers for simultaneous detection of current and electrog
enerated chemiluminescence is considered. (C) 1999 Elsevier Science B.V. Al
l rights reserved.