Highly sensitive determination of trace copper in food by adsorptive stripping voltammetry in the presence of 1,10-phenanthroline

A highly sensitive, rapid, simple and selective adsorptive stripping assay for the determination of trace copper(II) is proposed. The methodology is based on the adsorptive accumulation of copper(II)-1,10-phenanthroline complexes onto a glassy carbon electrode, followed by oxidation of the adsorbed species by voltammetric scanning using square-wave voltammetry. The influences of experimental variables on the sensitivity of the proposed method, such as the effects of pH, ligand concentration, accumulation time, accumulation potential and interferences, were investigated. Under optimal conditions, the proposed method showed linearity from 0.1 ng mL(-1) to 50 ng mL(-1). The 3 S/N detection limits were 0.0185 ng mL(-1), and the relative standard deviations (n = 10) were 0.09-4.71% for intra-day and 0.05-7.14% for inter-day analyses, respectively. The application of the proposed method to the direct analysis of food samples yielded results that agreed with those obtained from including inductively coupled plasma-optical emission spectrometry (ICP-OES) assays according to a paired t-test. The results are a step toward the development of an alternative and reliable analytical method for food research, which requires the direct determination of copper. (c) 2013 Elsevier B.V. All rights reserved.