Evaluation of a carbon paste electrode modified with organofunctionalised SBA-15 nanostructured silica in the simultaneous determination of divalent lead, copper and mercury ions

The performance of a carbon paste electrode (CPE) modified with SBA-15 nanostructured silica organofunctionalised with 2-benzothiazolethiol in the simultaneous determination of Pb(II), Cu(II) and Hg(II) ions in natural water and sugar cane spirit ( cachaça) is described. Pb(II), Cu(II) and Hg(II) were pre-concentrated on the surface of the modified electrode by complexing with 2-benzothiazolethiol and reduced at a negative potential (−0.80 V). Then the reduced products were oxidised by DPASV procedure. The fact that three stripping peaks appeared on the voltammograms at the potentials of −0.48 V (Pb 2+), −0.03 V (Cu 2+) and +0.36 V (Hg 2+) in relation to the SCE, demonstrates the possibility of simultaneous determination of Pb 2+, Cu 2+ and Hg 2+. The best results were obtained under the following optimised conditions: 100 mV pulse amplitude, 3 min accumulation time, 25 mV s −1 scan rate in phosphate solution pH 3.0. Using such parameters, calibration graphs were linear in the concentration ranges of 3.00–70.0 × 10 −7 mol L −1 (Pb 2+), 8.00–100.0 × 10 −7 mol L −1 (Cu 2+) and 2.00–10.0 × 10 −6 mol L −1 (Hg 2+). Detection limits of 4.0 × 10 −8 mol L −1 (Pb 2+), 2.0 × 10 −7 mol L −1 (Cu 2+) and 4.0 × 10 −7 mol L −1(Hg 2+) were obtained at the signal noise ratio (SNR) of 3. The results indicate that this electrode is sensitive and effective for simultaneous determination of Pb 2+, Cu 2+ and Hg 2+ in the analysed samples.