Electrocatalytic oxidation of thiocyanate, l-cysteine and 2-mercaptoethanol by self-assembled monolayer of cobalt tetraethoxy thiophene phthalocyanine

Catalytic activity of a self-assembled monolayer (SAM) of cobalt tetra ethoxythiophene phthalocyanine (CoTEThPc-SAM) complex towards oxidation of thiocyanate (SCN⁻), l-cysteine (CYS) and 2-mercaptoethanol (2-ME) is reported. The oxidation of thiocyanate occurs via a two electron transfer, whereas l-cysteine and 2-ME require 1 electron. The oxidation of thiocyanate is catalysed by ring based processes, while l-cysteine is catalysed by both Co^III/Co^II process and by ring based processes. 2-ME is catalysed by Co^III/Co^II process. The oxidation of thiocyanate on CoTEThPc was performed in acid media instead of basic media commonly employed. The reaction order was found to be unity for all the analytes, showing that only one molecule of analyte interacts with one molecule of the catalyst during the rate determining step.     

Electrocatalysis of oxidation of 2-mercaptoethanol, l-cysteine and reduced glutathione by adsorbed and electrodeposited cobalt tetra phenoxypyrrole and tetra ethoxythiophene substituted phthalocyanines

Catalytic activity of cobalt tetra ethoxythiophene and cobalt tetra phenoxypyrrole phthalocyanine complexes towards oxidation of 2-mercaptoethanol, l-cysteine and reduced glutathione is reported. It was found that the activity of the complexes depends on the substitution of the phthalocyanine ring, pH, film thickness and method of electrode modification. The high electrocatalytic activity obtained with adsorbed complexes in alkaline medium clearly demonstrates the necessity of modifying bare carbon electrodes to endow them with the desired behaviour.     

Electro-catalyzed oxidation of reduced glutathione and 2-mercaptoethanol by cobalt phthalocyanine-containing screen printed graphite electrodes

Electro-catalytic behavior of screen printed graphite electrodes modified with cobalt phthalocyanine (CoPc) towards the oxidation of reduced glutathione (GSH) and 2-mercaptoethanol (2-ME) is reported. We find, by using cyclic voltammetry, that the oxidation of 2-ME occurs at 0.2 V vs Ag/AgCl and − 0.3 vs Ag/AgCl V at pH = 7 and pH = 13, respectively and that of GSH occurs at 0.4 V vs Ag/AgCl and 0.0 V vs Ag/AgCl at pH = 7 and 13, respectively. The electro-catalytic activity depends on the method of electrode modification and the amount of catalyst incorporated in the ink used to fabricate the SPCEs. The highest activity was obtained with electrodes prepared with 2.5% (w:w) of CoPc.