Simultaneous determination of ultra-trace lead and cadmium at a hydroxyapatite-modified carbon ionic liquid electrode by square-wave stripping voltammetry

In this paper, a hydroxyapatite-modified carbon ionic liquid electrode (HAP-CILE) for the simultaneous determination of lead and cadmium was developed. The hydroxyapatite which combines with ionic liquid plays an important role in remarkable responses of metals. Trace analysis of the selected heavy metals was performed by square-wave anodic stripping voltammetry (SWASV). The oxidation of two metals yielded well-defined, separated square-wave peak currents. The peak currents at about −0.34 V for Pb2+ and −0.88 V for Cd2+ were measured. The affecting factors containing supporting electrolyte, pH of solution, accumulation time, deposition potential, amount of hydroxyapatite and possible interferences were investigated. The sensor exhibited linear behavior in the range of 1 × 10−9 mol L−1 to 1 × 10−7 mol L−1 for lead and cadmium (correlation coefficients: 0.995 and 0.997, respectively) with detection limits of 2 × 10−10 mol L−1 for lead and 5 × 10−10 mol L−1 for cadmium. The results indicate that the sensor is sensitive and effective for the simultaneous determination of lead and cadmium.