Square Wave Voltammetry for Analytical Determination of Cadmium in Natural Water Using Ca10(PO4)6(OH)2-Modified Platinum Electrode

This paper reports on the development of a novel electrochemical assay for cadmium (II) in natural water, which involves the use of disposable hydroxyapatite modified platinum electrode (HAP/Pt). Cadmium (II) was preconcentrated on the surface of the modified electrode and adsorbed onto HAP and oxidized at E = –680 mV. The HAP-modified platinum electrode exhibited superior performance in comparison to the platinum electrode and surprisingly, yielded a higher electrochemical response. The best defined anodic peak was obtained with 0.2 mol L KNO3 pH 5.0 after 25 min of accumulation time. Using these conditions, the calibration plot was linear over the range 1 × 10 to 5 × 10 mol L Cd. The precision was examined by carrying out eight replicate measurements at a concentration of 2.5 × 10 mol L; the coefficient of variation was 2.9%. The method was applied to the determination of the analyte in river water samples. The interfereence of other metal ions on the voltammetric response of Cd(II) was studied. The HAP films was clearly observed in the SEM images and characterized by X-ray diffraction, IR spectroscopy and chemical analysis.