IN-SITU UV-VIS AND CD THIN-LAYER SPECTROELECTROCHEMISTRY STUDY OF THEELECTROCHEMICAL-BEHAVIOR OF L-NORADRENALINE IN ALKALINE-SOLUTION

Electrochemical redox behavior of noradrenaline in alkaline solution o n a glassy carbon electrode has been investigated by in situ UV-vis an d CD spectroelectrochemistry by using a long optical path thin-layer c ell. The experimental data were processed by using a double logarithmi c method of analysis together with nonlinear regression which confirme d that the first step in both the oxidation of noradrenaline and reduc tion of noradrenochrome is a two-electron irreversible process governe d by an EE mechanism. The kinetic parameters of the electrode reaction s, i.e., charge transfer coefficient and the number of electrons trans ferred, alpha(1)n(1) = 0.11 and alpha(2)n(2) = 0.23, formal potentials modified with kinetics, E-1(0') = 0.65 (+/- 0.01) V and E-2(0') = 0.7 2V and standard rate cnstants, k(1)(0) = 7.0(+/-0.5)x10(-5) cm s(-1), for the first and second steps in the oxidation process of noradrenali ne, and similarly, alpha(1)n(1) = 0.33, alpha(2)n(2) = 0.58, E-1(0') = 0.37(+/-0.01) V, E-0' = -0.25 (+/-0.01) V and k(1)(0) approximate to k(2)(0) = 1.06 (+/-0.05)x10(-4) cm s(-1) for the first and second step s in the reduction process of noradrenochrome were also determined.