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 electro des. Linear sweep and differential pulse voltammetry, along with now i njection analysis in the amperometric detection mode, were used to stu dy the reaction at neutral pH as a function of the potential sweep rat e, analyte concentration, and electrolyte composition. Comparison expe riments were performed using polished glassy carbon. Azide undergoes a n irreversible oxidation (1 e(-)/equiv) at both of these carbon electr odes, presumably with nitrogen as the primary product. A linear dynami c range of 3-4 orders of magnitude and a detection limit as low as 0.1 mu M (4.3 ppb) at a S/N = 3 were observed for diamond in the voltamme tric measurements. The now injection analysis results for diamond indi cated 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 general ly reproducible from film to film, and the background signal and signa l-to-background ratio were extremely stable for up to 12 h of continuo us use. The results demonstrate that this new electrode material serve s as an analytically useful substrate for the detection of azide anion and exhibits superior performance characteristics compared with glass y carbon.