Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: May 16, 2001
Publication Date: N/A
Technical Abstract: Vitamin E-active antioxidants exist in oilseeds as complex mixtures of closely related structures. Variations in the composition of these minor oil constituents have profound effects on oil quality and stability of frying oils. Development of a rapid micro technique with minimal solvent consumption is highly desirable for quality control in oil industries. In this study, antioxidant distributions of several oil varieties (e.g. rice bran oils, palm oils, soybean oils) were evaluated by capillary electrochromatography (CEC)-UV detection. The CEC instrument was interfaced with a polar reversed phase capillary column (25 cm x 75 um I.D). Initial attempts to use nonpolar reversed-phase columns were less satisfactory for the assessment of the title compounds. In a typical CEC experiment, voltage, temperature, and electrokinetic-injection settings were maintained at 20 kV, 25C, and 10 kV/2s, respectively. The detector was set at 292 nm. Of the numerous solvent systems tested, CEC with TRIS buffers in aqueous methanol yielded the best results. Prior to quantification, most oil samples required purification by solid phase extraction, saponification, or supercritical fluid extraction to remove interfering materials because of nonspecificity of UV detection. The CEC separation profiles of the lipid antioxidants were similar to those obtained by HPLC. However, the new technique greatly reduces the assay times (>50%) as well as the solvent amounts used (~95%). In addition, a significant improvement in component resolution was observed. The CEC results indicated that the total analyte levels in crude oils were nearly twice those found in RBD oils and that the concentration data were correlatable with their oxidative stability.