Critical Comparison of Paraffin Carbon Paste and Graphite-Poly(tetrafluorethylene) Composite Electrodes Concerning the Electroanalytical Behavior of Various Antioxidants of Different Hydrophobicity

Abstract

Universite´Libre de Bruxelles, Institut de Pharmacie, Campus Plaine CP 205/6, B-1050, Bruxelles, BelgiumReceived: August 4, 1997Final version: October 8, 1997AbstractThe voltammetric and flow-injection amperometric behaviors of several substances used as antioxidants in the food and pharmaceutical industriesat carbon paste electrodes, with paraffin as binding agent, and at graphite-40% PTFE composite electrodes were compared on the basis of thedifferent hydrophobicity of the antioxidants. Aqueous solutions, alcohol–water mixtures and oil-in-water-emulsions were used as working media.No voltammetric or flow-injection responses were obtained for high hydrophobic antioxidants (BHT, Irganox-1076 and Irganox-1010) at graphite–PTFE electrodes. On the contrary, carbon paste electrodes allowed the attainment of analytically useful signals for these compounds. A pulseamperometric detection (PAD) scheme should be applied in these cases for the cleaning of the electrode surface. The use of graphite-PTFEelectrodes seems to be advantageous for the less hydrophobic antioxidants such us propyl gallate and TBHQ. An adsorption process for PG and afaster electrode kinetic in the case of TBHQ were shown to occur by cyclic voltammetry at the PTFE composite electrode. Furthermore, thiselectrode allows the use of lower potentials for the amperometric detection of these compounds than the carbon paste electrode. Goodreproducibility of the successive amperometric responses was also observed. The mutual influence of the electrode surface composition and thelipophilic characteristics of the molecules tested is discussed.