Voltammetric and amperometric investigations of azide oxidation at the basal plane of highly oriented pyrolytic graphite

The electrochemical oxidation of dissolved azide anion has been investigated at the basal plane of highly oriented pyrolytic:graphite. Cyclic and linear sweep voltammetry and differential pulse voltammetry were employed to study the oxidation reaction mechanism in neutral pH as a function of the potential sweep rate, analyte concentration, and electrolyte composition and in the presence of adsorbed anthraquinone-2,6-disulfonate (2,6-AQDS), The linear dynamic range in the differential pulse voltammetric measurements was 4 orders of magnitude and the estimated limit of detection (SNR = 3) was similar to 2.3 x 10(-7) M (9.7 ppb). The electron-transfer kinetics for azide oxidation appear rapid at this surface, and the voltammetric features are independent of the fraction of exposed edge plane, the presence of surface oxides, the electrolyte composition, and the adsorption of 2,6-AQDS. The reaction is shown to proceed by an EC(dim) mechanism. Amperometric detection results for now injection analysis (FIA)and ion chromatography are also presented. A linear dynamic range of nearly 5 orders of magnitude, an estimated detection limit (SNR = 3) of 3.7 nM (0.16 ppb or 74 fmol injected), and a response variability of 2% or less were observed in the FIA measurements.