Development and Evaluation of a Normal Phase Liquid Chromatographic Method for the Determination of Tocopherols and Tocotrienols in Walnuts

Abstract

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 µg/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%).