Determination of tocopherol acetate in emulsified nutritional supplements by solid-phase extraction and high-performance liquid chromatography with fluorescence detection

The present paper deals with a method of solid-phase extraction of tocopherol acetate (TA, 49.6 μg/g) from emulsified nutritional supplements, which contains 50 kinds of compounds, followed by high-performance liquid chromatography (HPLC) with fluorescence detection The TA concentration is 5∼100 000 times lower than that of other compounds in the samples. Measuring the loading capacity of the larger amounts of vegetable oil onto the Bond Elut C18 cartridge was examined for the complete retention of smaller level of TA. A sample solution was applied to a solid-phase extraction cartridge and then TA was eluted by acetonitrile followed by HPLC. This method was suitable for the determination of TA in emulsified nutritional supplements. The proposed method was simple, rapid (analysis time: ca. 15 min), sensitive [detection limit: ca. 0.1 ng per injection (100 μl) at a signal-to-noise ratio of 3:1], and reproducible (relative standard deviation: ca. 2.5% (n=5)). The calibration graph of TA was linear in the range of 0.1 to 100 ng per injection (100 μl). Recovery of TA was over 90% by the standard addition method.