DIFFERENTIAL LINEAR SWEEP AND DIFFERENTIAL CYCLIC VOLTABSORPTOMETRY IN A LONG-PATH-LENGTH SPECTROELECTROCHEMICAL CELL - EQR, EIR AND ERCI'

The theory of differential linear sweep voltabsorptometry (DLSVA) and differential cyclic voltabsorptometry (DCVA) in long-path-length spect roelectrochemistry is presented for irreversible (Eir), quasi-reversib le (Eqr) and ErCi' mechanisms under conditions of semi-infinite diffus ion. It is concluded that this method may be suitable for estimating e lectrochemical parameters because it is more sensitive than the approa ch using an optically transparent electrode. All the theoretical resul ts are experimentally verified. The standard heterogeneous rate consta nt k(s) and the transfer coefficient alpha of two electrochemical quas i-reversible systems (methylene blue in 1.0 M HCl and indigo carmine i n 0.1 M HCl) were estimated using the simplex method and good fits bet ween theory and experiment were obtained. A system comprising K4Fe(CN) 6+ ascorbic acid in 0.5 M HNO3 + 0.5 M glycine buffer was utilized to test the theory for the ErCi' mechanism. The rate constant of the pseu do-first-order catalytic reaction was also estimated by simplex fittin g. The estimated results are in agreement with experimental values.