Available online at www.sciencedirect.com Talanta 75 (2008) 15–21 Evaluation of a carbon paste electrode modified with organofunctionalised SBA-15 nanostructured silica in the simultaneous determination of divalent lead, copper and mercury ions Ivana Cesarino a , Glimaldo Marino a , Jivaldo do Ros´ ario Matos b , ´ Eder Tadeu Gomes Cavalheiro a,∗ a Departamento de Qu´ ımica e F´ ısica Molecular, Instituto de Qu´ ımica de S ˜ ao Carlos, Av Trabalhador S˜ aocarlense, 400, Centro, CEP 13560-970, S ˜ ao Carlos, S ˜ ao Paulo, Brazil b Departamento de Qu´ ımica Fundamental, Universidade de S˜ ao Paulo, Cidade Universit´ aria Armando Salles Oliveira, S˜ ao Paulo(SP), Brazil Received 2 April 2007; received in revised form 19 June 2007; accepted 22 June 2007 Available online 1 July 2007 Abstract 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 (cacha¸ ca) 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. © 2008 Published by Elsevier B.V. Keywords: SBA-15 nanostructured silica; Carbon paste electrode; 2-Benzothiazolethiol; Cacha¸ ca; Well water 1. Introduction One-dimensional uniform tubular pores, in the form of hexag- onally arranged mesoporous SBA-15 silica, attracted much attention when it was first reported by Zhao et al. [1], due to their marked hydrothermal stability, amenability to synthesis in a wide range of pore sizes (4.6–30 nm), and particle morphologies as well as their potential applications in emergent areas, such as energy storage in doublelayer supercapacitors, catalytic support in fuel cell electrodes, adsorption of bulky molecules in liquid phase, improvement of selectivity and sensitivity in the prepa- ration of electrodes for electroanalysis, etc. [2–5]. Mesoporous ∗ Corresponding author. Fax: +55 16 3373 9987. E-mail address: cavalheiro@iqsc.usp.br ( ´ E.T.G. Cavalheiro). silica can be modified and functionalised by incorporation of organic groups in the silica structure via synthesis procedure and the immobilisation of organic substances that can be bonded to the silanol groups on the surface of mesoporous silica. A wide range of functional groups, such as thiols, amines, epoxides, imadizoles, chromophores, phenyls and alkyorganosilanes are reported to be incorporated [6–10]. Walcarius [11,12] presents extensive reviews about the prepa- ration and application of silica modified electrodes showing their importance as electroanalytical sensors. Electrochemical sensors based on stripping voltammetry use to be a useful technique for determining aqueous heavy metal concentrations. These sensors are usually sensitive, compact, low cost and easily integrated into field-deployable units [13–15]. Stripping voltam- metry for trace metal ions usually involves pre concentration of metal ions at an electrode surface, followed by quantification of 0039-9140/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.talanta.2007.06.032