Electrochemical determination of vitamin E in margarine, butter and palm oil
Journal of the Science of Food and Agriculture 26(4): 393-399
ISSN/ISBN: 0022-5142 PMID: 1152432 DOI: 10.1002/jsfa.2740260403
A simple, rapid and reproducible method is described for the analysis of tocopherols in margarine, butter and palm oil. The method involves saponification, extraction of the unsaponifiable material and direct voltammetric determination. No separation technique is necessary. Two indicator electrodes, glassy carbon (GCE) and carbon paste (CPE), were employed in this work, GCE in ethanol-benzene (2:1) medium and CPE in 75% ethanol. The CPE gives over 10 times as much current as the GCE for a given tocopherol concentration. The GCE's high residual current in aqueous medium makes it impractical in 75% aqueous ethanol and the CPE's solubility in benzene restricts its usage in ethanol-benzene medium. Slight turbidity does occur sometimes when the unsaponifiable material of the samples is dissolved in 75% ethanol but this seems not to interfere in subsequent analysis. Increase in ethanol content to 90% gives a clearer solution and higher background, but no appreciable difference in the results. The results obtained by use of both electrodes are given and shown to be in close agreement with previously published results.