Characterization of a carbon paste electrode modified with tripolyphosphate-modified kaolinite clay for the detection of lead

We report about the use of carbon paste electrode modified with kaolinite for analytical detection of trace lead(II) in domestic water by differential pulse voltammetry. Kaolinite clay was modified with tripolyphosphate (TPP) by impregnation method. The results show that TPP in kaolinite clay plays an important role in the accumulation process of Pb(II) on the modified electrode surface. The electroanalytical procedure for determination of Pb(II) comprised two steps: chemical accumulation of the analyte under open-circuit conditions, followed by electrochemical detection of the pre-concentrated species using differential pulse voltammetry. The analytical performance of this system has been explored by studying the effects of preconcentration time, carbon paste composition, pH, supporting electrolyte concentration, as well as interferences due to other ions. The calculated detection limit based on the variability of a blank solution (3s_b criterion) for 10 measurements was 8.4 × 10⁻⁸ mol L⁻¹, and the sensitivity determined from the slope of the calibration graph was 0.910 mol L⁻¹. The reproducibility (RSD) for five replicate measurements at 1.0 mg L⁻¹ lead level was 1.6%. The results indicate that this electrode is sensitive and effective for the determination of Pb²⁺.