Development and evaluation of a normal phase liquid chromatographic method for the determination of tocopherols and tocotrienols in walnuts

A high performance liquid chromatographic (HPLC) method for the determination of tocopherols and tocotrienols in walnut samples is described. The compounds were extracted with n-hexane, using a simple solid-liquid extraction procedure. Tocol was used as internal standard and BHT as anti-oxidant. The chromatographic separation was achieved using an Inertsil 5 SI normal phase column operating with isocratic elution of n-hexane/1,4-dioxane (96.5: 3.5, v/v), at a flow rate of 0.7 mL/min. The effluent was monitored by a series arrangement of a diode-array detector followed by a fluorescence detector, The detection limits were low, between 0.037 and 0.266 mug/mL. The method was precise (% CV less than 2.8%), accurate (% CV less than 5.6%), and, as a general rule, the recovery values were high (mean values ranging from 93.4% to 104.0%).