Automated analysis for vitamin E in butter by coupling sample treatment – continuous membrane extraction – liquid chromatography with electrochemical detection Original Research Article

An automated procedure for the determination of vitamin E in samples of butter with minimum sample manipulation has been developed. Following dissolution of the samples in a micellar medium (methanol–Triton X-100–water), on-line sample treatment involving alkaline hydrolysis is coupled with a separation and enrichment system in a cell containing a silicone membrane; the analyte-rich phase is finally connected to a liquid chromatographic analytical system – using a C18 column – with electrochemical detection controlling the whole system automatically. The proposed procedure has been successfully applied to the determination of vitamin E in samples of butter, using 2,2,5,7,8-pentamethyl-6-chromanol as internal standard. The coefficient of variation obtained was 6.7% for a inter-day assay.