Voltammetric detection of traces of copper using a carbon paste electrode modified with tetraphenylporphyrin

The voltammetric detection of copper(II) was carried out at a carbon paste electrode (CPE) modified with tetraphenylporphyrin (TPP). The analysis procedure consisted of an open circuit preconcentration step in stirred sample solution. This was followed by medium exchange to a pure electrolyte solution (Britton-Robinson buffer pH = 6) where the accumulated copper(II) was reduced at -0.8 V vs. Hg/Hg2SO4 and subsequently an anodic potential scan was effect to obtain the voltammetric peak. The parameters and conditions such as pH of the analyte solution and supporting electrolyte, preconcentration time, CPE composition, its activation and regeneration, and others, were studied in detail. The detection limit of the proposed procedure was found to be 2.0 x 10(-9) mol l(-1) of Cu(II) in the analyte solution for a proconcentration time of 12 min. Applying suitable preconcentration times, a linear calibration graph from 9.0 x 10(-8) to 5.0 x 10(-5). mol l(-1) of Cu(II) was established. Multiple determinations (n = 8), following a preconcentration-measurement-regeneration cycle, gave a relative standard deviation of 4.5% at Cu(II) concentration of 1.0 x 10(-7) mol l(-1). The proposed method was applied to the determination or Cu(II) in a real sample of residue solution after extraction and a mineral sample of Jinchuan Corporation.