title: Voltammetric determination of cocaine in confiscated samples using a cobalt hexacyanoferrate film-modified electrode.
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 NaClO(4) 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 NaClO(4) 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 x 10(-4) to 1.5 x 10(-3)mol L(-1), with a linear correlation coefficient of 0.994 and a detection limit of 1.4 x 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.
authors.affiliation: Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Departamento de Química, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Erica Naomi
authors.initials: EN
authors.lastname: Oiye
authors.forename: Natalia Biziak de
authors.initials: NB
authors.lastname: Figueiredo
authors.forename: José Fernando de
authors.initials: JF
authors.lastname: Andrade
authors.forename: Heloisa Maria
authors.initials: HM
authors.lastname: Tristão
authors.forename: Marcelo Firmino de
authors.initials: MF
authors.lastname: Oliveira