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Abstract
This paper describes an HPLC procedure for the determination of tocopherols and tocotrienols in crude and edible vegetable oils. The sample preparation only involves a dissolution of the oil in n-hexane and filtration. The chromatographic separation was achieved using a normal phase column LiChrosorb SI 60 (5 μm; 25.0 × 0.4 cm). Isocratic elution was carried out using n-hexane : 2-propanol (99.7:0.3). The effluent was monitored by using diode-array and fluorimetric detectors.
The determinations were performed in the following linear ranges: 0.5-7.5 μg/mL for α-tocopherol and β-tocotrienol; 0.5-10 μg/mL for β-tocopherol; and 0.5-15 μg/mL for α-tocotrienol, γ-tocopherol, γ-tocotrienol, and δ-tocopherol.
Extensive quality assurance of the proposed method was performed by the standard addition method in both crude and edible oil. For edible oil, the precision obtained (n=10) was better than 1.8, 2.0, and 1.4 CV% for α, β, and γ-tocopherol, respectively; for crude oil it was better than 1.9, 2.4, and 2.4% for α, β, and γ-tocopherol, respectively.
Furthermore, for edible oil the mean recovery values were between 96-116%, 58-69%, and 111-115% for α, β, and γ-tocopherol, respectively; for crude oil recovery values were between 85-95%, 63-66%, and 99-103% for the same tocopherols, respectively.
The proposed method appears to be an adequate method for quality control and helpful for authenticity verification by the official control in oil industry.