Determination of subnanomolar concentrations of cobalt by adsorptive stripping voltammetry at a bismuth film electrode

Procedures for trace cobalt determinations by adsorptive stripping voltammetry at in situ and ex situ plated bismuth film electrodes are presented. These exploit the enhancement of the cobalt peak obtained by using the Co(II)-dimethylglyoxime-cetyltrimethylammonium bromide-piperazine-N,N'-bis(2-ethanesulfonic acid) system. The calibration graph for an accumulation time of 120 s was linear from 2 x 10(-10) to 2 x 10(-8) mol L-1. The relative standard deviation from five determinations of cobalt at a concentration of 5 x 10(-9) mol L-1 was 5.2%. The detection limit for an accumulation time of 300 s was 1.8 x 10(-11)supercript stop mol L-1. The proposed procedure was applied to cobalt determination in certified reference materials and in tap and river water samples.