Study on catalytic adsorptive stripping voltammetry of trace cobalt at bismuth film electrodes

Bismuth film electrodes (BiFE) prepared by plating a glassy carbon support ex situ from a solution containing 0.5 M LiBr and 1 M HCl was tested for the determination of cobalt traces using adsorptive stripping voltammetry (AdSV) and catalytic adsorptive stripping voltammetry (CAdSV). AdSV enables one to determine cobalt as the Co(II)-dimethylglyoximate (Co-DMG) complex down to 0.3 mug/L Co. Addition of NaNO2 to the solution containing dimethylglyoxime in ammonia buffer provides a 15-fold enhancement of the voltammetric signal of cobalt due to the catalytic effect occurring during the reduction of Co(II)-DMG. Utilization of the bismuth film electrode under optimized conditions assures a stable catalytic adsorptive stripping voltammetric response for Co, with an extremely high sensitivity (1.75 muA/(mug/L)), good precision (RSD=3%), and a low detection limit (0.07 mug/L Co with 60 s of adsorptive accumulation). The results of the measurement of the catalytic cobalt response in the presence of DMG and nitrite under hydrodynamic amperometric conditions have shown the BiFE to be an attractive and suitable tool for the rapid determination of cobalt at low mug/L level in both batch and flow systems.