Simultaneous determination of eight vitamin E isomers and α-tocopherol acetate in functional foods and nutritional supplements by gas chromatography – mass spectrometry

Abstract

A rapid and efficient gas chromatography-mass spectrometry (GC-MS) has been developed for determination of eight VE isomers including α-, β-, γ-, δ-tocopherols and tocotrienols, as well as α-tocopherol acetate in functional foods and nutritional supplements. The vitamin E isomers in samples were directly extracted without saponification with mixed solvents of methanol and hexane (7 : 3,v/v). Good separation was achieved using a VF-5MS column (30 m × 0.25 mm, 0.25 μm) within 13 min. The mass spectrometer was operated in both full scan mode and SIM mode using electron impact ionization. Qualitative detection was based on characteristic ion pairs and retention time. Dibenzanthracene was used as an internal standard for quantification measurement. The linear ranges of the method were from 0.1 to 40 μg mL⁻¹ with the correlation coefficients greater than 0.997. The detection limits ranged from 0.09 ng mL⁻¹ to 0.46 ng mL⁻¹, and the quantification limits were from 0.29 ng mL⁻¹ to 1.52 ng mL⁻¹. The intra-day and inter-day relative standard deviations (RSDs) of the method (for 1 μg mL⁻¹ standard solution) were in the range of 4.9% to 8.0% and 2.1% to 4.9%, respectively. The average recoveries of the method ranged from 83.2% to 107%, with the RSDs from 1.1% to 8.4%. The method has been applied for the determination of VE isomers and α-tocopherol acetate in functional foods and nutritional supplements with satisfactory results.