Electrochemical determination of lead(II) using a montmorillonite calcium-modified carbon paste electrode

Utilizing the fascinating properties of montmorillonite calcium (MMT-Ca), such as huge cationic exchange capacity, strong adsorptive ability, high chemical and mechanical stability, an MMT-Ca modified carbon paste electrode (CPE) was constructed for the sensitive determination of Pb2+. In 0.01 mol . L-1 HCl, Pb2+ was firstly exchanged and accumulated on an MMT-Ca modified CPE surface and secondly reduced to Pb at - 0.90V. In the following potential sweep from - 0.90 to - 0.50V, reduced Pb was oxidized, resulting in an obvious stripping peak at - 0.58V. After optimizing the parameters, such as determining medium, content of MMT-Ca, accumulation potential and time, an electrochemical method was developed for the analysis of Pb2+. Compared with bare CPE, the MMT-Ca modified CPE significantly enhances the sensitivity of Pb2+ analysis. The limit of detection is evaluated to be 6.0 x 10(-9) mol L-1 Pb2+. Finally, this method was successfully employed to determine trace levels of Pb2+ in water samples.