Utilising gallium for enhanced electrochemical copper analysis at the bismuth film electrode

A sensitive anodic stripping voltammetric procedure at the bismuth film electrode (BFE) for trace analysis of copper (II) in the presence of gallium is presented. The new protocol circumvents the problems of overlapping stripping signals between copper and bismuth that previously hampered the analysis of copper at the BFE. The results illustrate that the addition of gallium not only improves the reproducibility of the bismuth stripping signal but also facilitates much improved resolution between the stripping signals of bismuth and copper. Investigations into the effect of gallium on the stripping response of copper and bismuth were studied showing a 4:1 gallium:copper mole ratio produces optimum signals from bismuth and copper indicating a possible stoichiometric relationship. Optimisation of other key variables including electrolyte composition, accumulation parameters and appropriate waveform settings were studied and optimised. The optimised procedures show a range of linear calibration plots (R2>0.994) ranging from 2 to 500 microg L(-1) and the relative standard deviation for a solution containing 100 microg L(-1) copper was 3.7% (n=10). Utilising an accumulation time of 300 s the limit of detection was 1.4 microg L(-1) (S/N=3). This technique was successfully applied to the analysis of copper in tap water representing the first successful copper determination in real samples using the BFE.