In Situ Electro-organic Synthesis and Functionalization of Catechol Derivative on Carbon Black and Its Interference-free Voltammetric pH Sensor Application ∗

Abstract

We report an easy electrochemical route for preparing a catechol derivative (di-ferulyl sesamol derivative, designated as CA-Fer) functionalized low-cost carbon black (CB) modified electrode in a neutral pH buffer solution. As synthesized precursor organic compound, CA-Fer has been electrochemically oxidized over the CB by potential cycling treatment in pH 7 PBS that leads to a high redox active CA-Fer-catechol derivative (CB@CA-Fer-Redox), which exhibited a well-defined and stable surface-confined redox response at Eo’ = 0.150 V vs Ag/AgCl with a surface excess value = 50.46 nmol cm−2. Unlike the conventional redox active mediators, GCE/CB@CA-Fer-Redox modified electrode has failed to show any mediated oxidation/reduction response to various electro-active biochemicals and chemicals, viz., ascorbic acid, glucose, cysteine, caffeic acid, hydrazine, hydrogen peroxide, uric acid, dopamine, creatinine, urea, nitrite, sulfide and sulfate ions, depicting a clear advantage of using it as a voltammetric pH sensor for real-time applications. The modified electrode showed a linear voltammetric potential signal against pH in a window, 3–11, with a slope value of (∂Ep/∂pH) = −59 ± 3 mV pH−1. As an independent study, a CA-Fer-Redox modified three-in-one screen printed electrode was developed, and a sensitive voltammetric pH analysis of some chemical biochemical real sample systems were demonstrated.