Potentiometric Detection of 2-Mercaptobenzimidazole and 2-Mercaptobenzothiazole at Cobalt Phthalocyanine Modified Carbon-Paste Electrode

Abstract

A potentiometric method has been developed for determination of 2-mercaptobenzimidazole (MBIM) and 2-mercaptobenzothiazole (MBTH) based on cobalt phthalocyanine (CoPc) modified carbon-paste electrode. We show that the CoPc-modified electrode acts as a catalyst for the electrooxidation of MBIM and MBTH, lowering the overpotential of the reaction by 250 to 400 mV, compared to the unmodified electrode. The faster rate of electron transfer results in a near-Nernstian behavior of the modified electrode and makes it a suitable potentiometric sensor for potentiometric detection of these sulfhydryl compounds. The potential response of the electrode to the sulfhydryl compounds has a linear dynamic range between 1×10–6 and 3.6×10–3 M with a near Nernstian slope of 50 to 54 mV/decade of concentration and a detection limit of 5×10–7 M. The electrode retains its full activity for at least a month. The potentiometric response mechanism toward sulfhydryl compounds is discussed and a mechanistic model for the electrode response is given.