Application of Direct Solvent Extraction to the LC Quantification of Vitamin E in Peanuts, Peanut Butter, and Selected Nuts

Abstract

Direct solvent extraction with hexane:ethyl acetate (90:10, v/v), saponification, and Soxhlet extraction with hexane were evaluated for their usefulness as extraction methods to determine vitamin E in peanuts and peanut butters. The direct solvent extraction procedure yielded higher values for each tocopherol homolog in peanut and peanut butter compared to the other methods. Coupling of the rapid, direct solvent extraction with normal phase chromatography on Si 60 provides a highly reproducible procedure to quantitate vitamin E in peanuts and peanut products. The overall % recoveries (means ± S.D.) of this study for α-, β-, γ-, and δ-tocopherol were 99.9 ± 3.29, 100.4 ± 11.7, 98.9 ± 5.94, and 100.3 ± 4.87, respectively. Limits of detection and limits of quantitation were 0.21, 0.06, 0.11, and 0.08 ng and 0.39, 0.14, 0.23, and 0.13 ng, respectively, for α-, β-, γ-, and δ-tocopherol. Repeatability, reproducibility, and accuracy of the methods were excellent with % CVs for accuracy of 1.19 (α-T), 1.55 (γ-T), and 2.69 (δ-T). Accuracy was not acceptable for β-T due to its extremely low concentration in the peanut and because peak purity was not obtained for β-T. The method was applied to other seeds with good success. Major homologs were γ-T in peanuts, pecans, cashews, walnuts, and pistachio; α-T in almonds; and α-T3 in macadamia.