Carbon paste electrode plated with lead film. Voltammetric characteristics and application in adsorptive stripping voltammetry

摘要

A lead film plated in situ at a carbon paste support was tested as a novel, potential electrode for adsorptive stripping voltammetric determination of cobalt traces in an ammonia buffer solution. To show the practical applicability of the new electrode, a catalytic adsorptive Co system in a supporting electrolyte containing 0.1 M ammonia buffer, 5 x 10(-4) M nioxime and 0.25 M nitrite was selected and investigated as a model solution. Pb and Co ions were simultaneously accumulated in situ on the electrode surface: Ph ions electrochemically at - 1.3 V) and then at -0.75 V, at which potential the Co(II)-nioximate complex was also pre-concentrated via adsorption. Instrumental parameters, such as the time of nucleation and formation of Pb film deposits, the time of accumulation of the Co-nioxime complex at the PbF/CPE, and the procedures of electrode regeneration, were optimized to obtain good reproducibility and sensitivity of the Co response. The optimized procedure yields favorable and highly stable stripping responses with good precision (RSD = 3% for a 5 x 10(-8) M Co) and good linearity (up to 5 x 10(-7) M, coefficient of determination, R = 0.996). The detection limit was 4 x 10(-10) M Co (0.023 mu g L-1) for an accumulation time of 120 s. The method enables the determination of Co in the presence of high excesses of Ni or Zn. The voltammetric data were correlated with the structural characterization by scanning electron microscopy (SEM) and X-ray fluorescence spectroscopy (XRF).