Oxidation of Azide Anion at Boron-Doped Diamond Thin-Film Electrodes

The oxidation of dissolved inorganic azide anion in aqueous media was investigated using high-quality, boron-doped diamond thin-film electrodes. Linear sweep and differential pulse voltammetry, along with flow injection analysis in the amperometric detection mode, were used to study the reaction at neutral pH as a function of the potential sweep rate, analyte concentration, and electrolyte composition. Comparison experiments were performed using polished glassy carbon. Azide undergoes an irreversible oxidation (1 e-/equiv) at both of these carbon electrodes, presumably with nitrogen as the primary product. A linear dynamic range of 3−4 orders of magnitude and a detection limit as low as 0.1 μM (4.3 ppb) at a S/N = 3 were observed for diamond in the voltammetric measurements. The flow injection analysis results for diamond indicated a linear dynamic range of 5 orders of magnitude and a detection limit of 8 nM (0.3 ppb) at a S/N = 3. The diamond response was generally reproducible from film to film, and the...