Chromatography

Natural tocols, which is a powerful antioxidant, are classifi ed into two major homologues series, the tocopherols and tocotrienols. Each of these homologue consists of α-, β-,
- and δ- isoforms. While tocopherols are more commonly found in natural plants, the availability of tocotrienols is more limited. Studies have found that both tocopherols and tocotrienols are present in palm oil. In fact, palm oil is known to contain highest amount of natural tocotrienols. Earlier studies documented that palm tocols consist of α-tocopherol (α-T), α-tocotrienol (α-T3), γ- tocopherol (γ-T), γ-tocotrienol (γ-T3)

and δ-tocotrienol (δ-T3). Studies in later years reported the presence of α-tocomonoenol (α-T1) in palm oil. Accuracy and reliability of analyses for tocols have always been a cause for concern. Th is is due to the fact that the tocols are highly potent antioxidative compounds and thus, are easily susceptible to oxidation or degradation. Th e most debated question remained the use of individual standards for the analyses of α-, β-, γ- and δ-tocotrienols. Th e question on the concentration of the standards were oft en raised as the tocotrienols, especially δ-tocotrienol is easily susceptible to oxidation. Th e scarcity of tocotrienols and tocomononeol standards also contributed to the diffi culty in analyses and calibrations. Offi cial AOCS method recommended

the use of α-tocopherol as reference in the absence of the tocotrienols standards, which is a common practice. However, this is

oft en not accepted by the industry players mainly due to the question on the diff erent response of the individual tocopherols and

tocotrienols in UV spectroscopic analyses. In addition, the concentration of α-tocomonoenol is oft en not reported although

its presence is quite signifi cant in palm oil. Moreover, to date, there is no reliable offi cial method and authentic standards for such analyses. Th e American Oil Chemists’ Society (AOCS) has documented a method for the analyses of tocopherols and tocotrienols, however, the method is deemed useful only when the standards for the individual tocopherols and tocotrienols are available for calibration. Th e present paper reports on a comprehensive and reliable method for the HPLC analyses of tocopherols, tocomonoenol and tocotrienols in palm oil, taking into consideration the limit of detection, limit of quantitation, linear range of analyses as well as the calibration of the tocols in the absence of authentic standards.