Determination of phylloquinone in oils, margarines and butter by high-performance liquid chromatography with electrochemical detection

Abstract

A high-performance liquid chromatographic (HPLC) method for the determination of phylloquinone in oils and margarines following purification of hexane solutions of oils or hexane extracts of margarines by straight-phase semipreparative HPLC is described. Phylloquinone was quantified by reverse-phase HPLC with a dual-electrode electrochemical detector operating in the redox mode. Menaquinone-4 (MK-4) was used as an internal standard. By this method the phylloquinone present in the main oils and margarines available on the Finnish market was determined.The same method, but without the internal standard, was applied to butter. The detection limit of phylloquinone was 50 pg per injection, and its recovery when added to oil and margarine samples and quantified by the internal standard method was 98% and 102%, respectively. The mean phylloquinone content of oils ranged from 1·5 μg (refined rapeseed oil) to 0·10 μg (sunflower oil). In the soft margarines with 80% fat, the phylloquinone levels were 0·89 – 1·1 μg g −1. The phylloquinone content of margarines with 40% and 60% fat correlated with their fat content. Blended and hard margarines contained less phylloquinone than the soft margarines with corresponding fat contents. The contribution of oils and margarines to the average daily dietary intake of phylloquinone in Finland was estimated to be approximate 40 μg.