Study of Electrochemical Behaviour of Carotenoids in Aqueous Media

Focus of this research was electrochemical study of beta-carotene, astaxanthin and lutein in aqueous media. Compounds were investigated on paraffin impregnated graphite electrode (PIGE) in 0.1 M HClO4 aqueous electrolyte using square-wave voltammetry (SWV) with pulse amplitude of 50 mV and step potential of 2 mV. Voltammetry of immobilized microparticles (VIM) allowed determination of beta-carotene and astaxanthin as solids immersed in aqueous electrolyte. Results obtained with SWV revealed oxidation peaks at 0.88 V and 1.09 V versus Ag/AgCl for beta-carotene and astaxanthin, respectively. To obtain additional information about their behaviour, stripping voltammetry microprobe (SPV) was employed. With this technique the responses of astaxanthin, beta-carotene and lutein exhibit three peaks (-0.345 V, 0.47 V and 0.65 V), two peaks (0.477 V and 0.725 V) and a single peak at 0.687 V, respectively. Based on these results, antioxidant activity of these carotenoids is in order: astaxanthin > beta-carotene > lutein. Good dose-response relationship between carotenoid concentrations precipitated on PIGE and net peak current was obtained, but in rather narrow concentration range for each compound.