Mechanism of 3,4-dihydroxybenzaldehyde electropolymerization at carbon paste electrodes - Catalytic detection of NADH

Cyclic voltammetry was used to study 3,4-dihydroxybenzaldehyde (3,4-DHB) electropolymerization processes on carbon paste electrodes. The characteristics of the electropolymerized films were highly dependent on pH, anodic switching potential, scan rate, 3,4-DHB concentrations and number of cycles. Film stability was determined in citrate/phosphate buffer solutions at the same pH used during the electropolymerization process. The best conditions to prepare carbon paste modified electrodes were pH 7.8; 0.0 less than or equal to E-apl less than or equal to 0.25 V; 10 mV s(-1); 0.25 mmol L-1 3,4-DHB and 10 scans. These carbon paste modified electrodes were used for NADH catalytic detection at 0.23 V in the range 0.015 less than or equal to [NADH] less than or equal to 0.21 mmol L-1. Experimental data were used to propose a mechanism for the 3,4-DHB electropolymerization processes, which involves initial phenoxyl radical formation.