Voltammetric detection of the interactions between RNO2○- and electron acceptors in aqueous medium at highly boron doped diamond electrode (HBDDE)

This paper describes the electrochemical behavior of the nitrofurazone (NFZ), in predominantly aqueous medium, in the absence and presence of glutathione (reduced form) (GSH), L-Cysteine (Cys) and O-2 using a highly boron doped diamond electrode (HBDDE). In presence of [Thiol] >= 3.7 x 10(-2) mol L-1 NFZ is directly reduced to RNO-Thiol adducts in an electrochemical process involving two electrons and two protons. On the other side, 02 acts as a RNO2 center dot- scavenger and the velocity constant for the reaction, kO(2), is 60 L mol(-1) s(-1). The process is catalytic and can be used to the analytical determination of NFZ in the range of 9.9 x 10(-7) <= [NFZ] <= 1.1 x 10(-5) mol L-1 at pH 8.0, with sensitivity of 2.2 x 10(6) mu A mol(-1) cm(-2) and detection limit of 3.4 x 10(-7) mol L-1. The analytical parameters were similar to those obtained at pH 4.0 using the direct reduction of NFZ to the respective amine derivative in a process involving six electrons and six protons. The characterization of NFZ global reduction process in aqueous medium and at relative low scan rate, 100 mV s(-1), was only possible due the intrinsic superficial characteristics of the HBDDE, which stabilize the RNO2 center dot- free radical, allowing to work in a large potential window, without losing the RNO2 center dot- oxidation signal. (c) 2006 Elsevier Ltd. All rights reserved.