Subtle adjustment of the cyclic potential on electro-activated glassy carbon electrodes for sensitive sensing of methyl parathion

Abstract

Facile electro-activated glassy carbon electrodes (e-GCEs), which are prepared in electrolyte solution with a certain potential for a few seconds, have been verified to improve analytical performance toward not a few electro-active molecules recently. Nevertheless, how and why the potential plays an important role is not clear, and has even not received enough consideration. In this paper, we found that the mode and the range of applied potential significantly impacted the sensitivity of methyl parathion (MP), which is a typical pesticide with the electro-active group of –NO₂. Compared with constant potential, the e-GCE with cyclic potential provided a much more stable baseline during MP detection. Additionally, the electro-oxidation peak current of MP at around −0.1 V on it was higher than another changeable potential (constant current). What's more interesting, with cyclic potential for 50 segments from −2 to 1.5 V, the peak current value increased by 30 times in comparison with a bare GCE, but only 2 times from −2 to 1 V. Then after systematic investigation including structures of the electrode surface and functional groups, we speculated that the produced group of O–CO in the process of activation and remaining groups of C–O and CO on the bare GCE surface are beneficial for adsorbing MP molecules leading to enhanced peak current. Employing the proposed e-GCE, the limit of detection of MP reached 0.015 μM and the reproducibility was perfect. This work elucidates the potent impact of electro-activation potential parameters on electroanalysis behaviors.