An amperometric sensor for <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-ascorbic acid based on graphite paste electrode

Abstract

An amperometric sensor for <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-ascorbic acid based on graphite paste electrode with and without incorporating tetracyanoquinodimethane (TCNQ) is described. DC cyclic voltammetry indicates that <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-ascorbic acid can be oxidized at very low potential (0 mV vs SCE). DC cyclic voltammetry of TCNQ modified graphite paste electrode shows two anodic peaks for the oxidation of -ascorbic acid due to diffusion current and catalytic current. The catalytic wave is obtained due to the mediated mechanism of electron exchange through TCNQ. The second order rate constant (0.14 x 10⁴ 1 mol^-1 s^-1) for the reaction between <img src='http://www.niscair.res.in/jinfo/small.gif' border=0>-ascorbic acid and TCNQ has also been calculated. The TCNQ modified electrode shows long term stability.