BIOSENSORS Anodic Stripping Voltammetric Determination of Mercury in Water Using a Chitosan-Modified Carbon Paste Electrode Luiz H. Marcolino-Junior, Bruno C. Janegitz, Bruna C. Lourenc ¸a ˜o, and Orlando Fatibello-Filho Departamento de Quı ´mica, Centro de Cie ˆncias Exatas e de Tecnologia, Universidade Federal de Sa ˜o Carlos, Sa ˜o Carlos-SP, Brazil Abstract: This paper describes the preparation and electrochemical application of a modified carbon paste electrode with chitosan for the determination of Hg(II) ions in water using anodic stripping voltammetry. Experimental parameters, including the pH of the supporting electrolyte, time and potential of accumulation and scan rate were inves- tigated. The best voltammetric response was observed for a paste composition of 60% (m/ m) of graphite powder, 20% (m/m) of chitosan and 20% (m/m) of mineral oil, with 0.1 mol/l NaNO 3 solution at pH 6.3 as supporting electrolyte, a preconcentration potential of 20.2 V, preconcentration time of 270 s and a scan rate of 25 mV/s. Under these optimal experimental conditions, the voltammetric signals were linearly dependent on the Hg(II) concentration in the range of 9.99  10 27 to 3.85  10 25 mol/l with a detection limit of 6.28  10 27 mol/l. Three “spiked” samples of water were evaluated using the proposed sensor, and results agreed with those obtained by a reference method at the 95% confidence level. Keywords: Hg(II), chitosan, stripping voltammetry, modified carbon paste electrode INTRODUCTION Chemical modification of electrodes is a field of growing interest in analytical chemistry (do Carmo et al. 2003). In recent years the construction and the Received 1 July 2007; accepted 1 September 2007 Address correspondence to Orlando Fatibello-Filho, Departamento de Quı ´mica, Centro de Cie ˆncias Exatas e de Tecnologia, Universidade Federal de Sa ˜o Carlos, Sa ˜o Carlos-SP, Brazil. E-mail: bello@dq.ufscar.br Analytical Letters, 40: 3119–3128, 2007 Copyright # Taylor & Francis Group, LLC ISSN 0003-2719 print/1532-236X online DOI: 10.1080/00032710701645463 3119