THE METHYL VIOLOGEN INCORPORATED ZEOLITE MODIFIED CARBON-PASTE ELECTRODE .1. ELECTROCHEMICAL-BEHAVIOR IN AQUEOUS-MEDIA - EFFECTS OF SUPPORTING ELECTROLYTE AND IMMERSION TIME

Methyl viologen (MV++) is incorporated into a zeolite modified carbon paste electrode (ZMCPE). The electrochemical behaviour of MV++ is examined in aqueous media with various supporting electrolytes (NaCl, NaBr and several tetraalkylammonium bromides) by cyclic voltammetry, chronoamperometry and chronocoulometry. Quantitative in situ determination of MV++ leaching from paste into the external solution is performed using square wave voltammetry. The thickness of the ZMCPE involved in the electrochemical reaction of MV++ has been found to increase with experiment time. This was not the case with unmodified carbon paste. The diffusion coefficient of free MV++ within a ZMCPE is calculated to be about 8 x 10(-11) cm2 s-1. This value increases (3 x 10(-10) cm2 s-1) when the paste is equilibrated in high purity water for several hours before being used to obtain the ''hydrated'' form of a ZMCPE.