Electrochemical study of antioxidants at a polypyrrole electrode modified by a nickel phthalocyanine complex. Application to their HPLC separation and to their FIA system detections

A polypyrrole electrode modified with a tetrasulfonated nickel(II) phthaloc yanine complex (GCE/PPy/NiPcTs) was used as amperometric electrochemical de tector in a flow injection system, in order to determine some antioxidants in foods. The lather were separated by HPLC and detected at the modified el ectrode. Previous investigations carried out in our laboratory employed thi s electrode and cyclic voltammetry (CV), obtaining excellent results, due t o an electrocatalytic effect on the oxidation of certain alimentary antioxi dants, such tert-butylhydroquinone (TBHQ), 3-tert-butyl-4-hydroxyanisole (B HA) and propylgallate CPG). In order to obtain good separation, the chromat ographic conditions were optimised. The geometry of the flow injection anal ysis (FIA) circuit and the reproducibility of the results were also optimis ed and, finally, the linear relationship between the signal and the concent ration was verified. The proposed procedure is more precise and accurate th an the conventional voltammetry methods. These results offer new analytical possibilities to this type of modified electrodes. The developed methods w ere applied to the determination of these antioxidants in commercial food. (C) 2000 Elsevier Science B.V. All rights reserved.