individually the peak current of lead, cadmium and zinc complexes increased almost linearly until 300 s. However, in the simulta- neously determination the peak current of lead, cadmium and zinc increased almost linearly with accumulation time until 90, 60 and 150 s, respectively and then decreased. On the other hand, the peak current of free CQ increased with accumulation time until 50 s and then decreased abruptly. This may be due to the fact that with increasing accumulation time Zn–CQ was competitive with Pb– CQ and Cd–CQ or consumes free CQ because it forms the more sta- ble complex. Considering the speed of the measurement, tads between 30 and 60 s were used for further studies, but in the anal- ysis of real samples with low analyte concentration longer times may be needed to achieve good sensitivity.
3.1.4. Comparison with others techniques and electrodes
Anodic stripping voltammetry (ASV), the most popular strip- ping voltammetric technique, is effective for the determination of trace amounts of metal ions. In adsorptive voltammetry higher sensitivity could be achieved in the presence of adequate ligand. In anodic voltammograms (Fig. 4A), the oxidation peaks of zinc, cadmium and lead are seen at