Simultaneous determination of tocopherols and tocotrienols in vegetable oils by GC-MS

Abstract

A simple and rapid gas chromatography-mass spectrometry (GC-MS) method was developed and validated for the simultaneous determination of α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols in vegetable oils. In this study, tedious sample pretreatments like saponification and derivatization, which are commonly used in previously published related methods, were not adopted. Tocopherols and tocotrienols were isolated from oil samples by ultrasonic extraction with methanol, then centrifuged and the supernatant was directly injected into the GC-MS system for analysis. The results showed that α-, β-, γ- and δ-tocopherols and α-, β-, γ- and δ-tocotrienols were well separated within 14 minutes. The instrumental limits of detection and quantification ranged from 0.3 to 2.5 ng mL⁻¹ and from 1.0 to 8.3 ng mL⁻¹, respectively. Calibration curves were well correlated (r² > 0.99) within the concentration range of 10 to 1000 ng mL⁻¹ for all eight compounds. Recovery tests were carried out by spiking virgin olive oil with standards at three concentration levels (10, 50 and 250 mg kg⁻¹), in which the average recoveries (n = 6) varied from 83.7% to 117.2%, with relative standard deviations ranging between 1.9% and 7.5%. The proposed method proved to be simple, sensitive and accurate, and was successfully applied to the determination of tocopherols and tocotrienols in vegetable oils.