Comparison of Tocopherol Contents in 13 Cold-Pressed Vegetable Oils Extracted from the Mini Screw Press Model T3 by RP-HPLC/FLD

Abstract

Optimization and validation of reversed-phase high-performance liquid chromatography with fluorescence detection (RP-HPLC/FLD) for the determination of tocopherols (, +, and α) were studied. In a simple sample preparation, oils were diluted in ethanol without saponification and injected directly onto Zorbax Eclipse plus C18. Acetonitrile and methanol (70:30) mixture was used as a mobile phase with a flow rate of 1mL/min. Fluorescence detection was operated at 296 nm of excitation wavelength and 330 nm of emission wavelength. Tocopherols were separated at 30 °C in less than 15 min after injection. The method showed to be good linear (r² > 0.999). Mean recoveries were 97.6-100.7%, with intra- and inter-day RSD less than 3.79 and 4.11%, respectively. The detection limits and quantification limits of the method were 0.08-0.21 and 0.23-0.71 μg/mL. The technique had been applied to analyze tocopherols in thirteen cold-pressed vegetable oils extracted using a mini screw press, which were virgin oils. The results showed statistically significant differences (P < 0.5) between the kinds of oil sample. The total tocopherols content ranges from 3.62 mg/kg in Japanese pumpkin oil to 1890.71 mg/kg in sacha inchi oil.