Electrocatalytic Oxidation of Dithionite at a Cobalt(II)tetrasulfonated Phthalocyanine and 5,10,15,20-Tetrakis-(4-sulfonatophenyl)porphyrin Cobalt(II) Modified Gold Electrode in Alkaline Solution

In this paper it is shown that the charge transfer kinetics of the oxidation of sodium dithionite at a gold electrode in alkaline solution can be increased by modifying this electrode with cobalt(II)tetrasulfonated phthalocyanine, sodium salt (CoTSPc) or 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin cobalt(II), tetrasodium salt (CoTSPor). Electrodeposition of these catalysts is discussed as well as the oxidation of sodium dithionite at these immobilized catalysts. Despite an observed acceleration in the charge transfer kinetics, sodium dithionite is still oxidized irreversibly. However, the improvement in kinetics has beneficial consequences in the field of electroanalysis of sodium dithionite. Comparison of the oxidation at bare gold and modified gold electrodes showed that with improved charge transfer kinetics at the modified electrodes a higher sensitivity and selectivity and a much lower detection limit is obtained.