Voltammetric determination of cocaine in confiscated samples using a cobalt hexacyanoferrate film-modified electrode |
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Authors: | rica Naomi Oiye Natalia Biziak de Figueiredo Jos Fernando de Andrade Heloisa Maria Tristo Marcelo Firmino de Oliveira |
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Institution: | aUSP – Faculdade de Filosofia Ciências e Letras de Ribeirão Preto – Departamento de Química – 14040-901 – Ribeirão Preto, São Paulo, Brazil;bSPTC – Nucleo de Perícias Criminalísticas de Ribeirão Preto – 14015-040 – Ribeirão Preto, São Paulo, Brazil |
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Abstract: | In this work, a fast, non destructive voltammetric method for cocaine detection in acetonitrile medium using a platinum disk electrode chemically modified with cobalt-hexacyanoferrate (CoHCFe) film is described. The deposition of CoHCFe film at platinum disk (working electrode) was carried out in aqueous solution containing NaClO4 at 0.1 mol L−1 as supporting electrolite. Stability studies of the film and subsequent voltammetric analysis of cocaine were made in acetonitrile medium with NaClO4 at 0.1 mol L−1 as supporting electrolite. A reversible interaction between cocaine and CoHCFe at the film produces a proportional decrease of original peak current, due to the formation of a complex between cocaine and cobalt íons, with subsequent partial passivation of the film surface, being the intensity of current decrease used as analytical signal for cocaine. A linear dependence of cocaine detection was carried out in the range from 2.4 × 10−4 to 1.5 × 10−3 mol L−1, with a linear correlation coefficient of 0.994 and a detection limit of 1.4 × 10−4 mol L−1. The analysis of confiscated samples by the proposed method indicated cocaine levels from 37% to 95% (m/m) and these results were validated by comparison to HPLC technique, being obtained good correlation between both methods. |
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Keywords: | Cocaine Cobalt hexacyanoferrate Forensic chemistry Chemically modified electrodes |
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