[Rapid determination of essential fatty acids of edible oils by conversion to their hydroxamic acids]

A simple and rapid HPLC method for the determination of essential fatty acids of edible oils was established. Oil samples were converted to their hydroxamic acids in a single step and analyzed without prior separation and purification. The chromatographic conditions were: Shim-pack CLC ODS, 5 microns, 150 mm x 6.0 mm i.d. column, 40 degrees C; MeOH: 0.02 mol/L NaH2PO4(pH 3.0) (81:19, V/V) as eluent and UV-213 nm detector. The linear range was 0.05-0.6 g/L, recovery was 96.93% and RSD was 1.80%(n = 4). The relative standard deviations for intra-day and inter-day assays were 1.24% and 1.62% respectively (n = 6). For 18:3, 18:2, 18:1, the difference between the derivatization yields from triglycerides and their methyl esters was almost one fold. That was confirmed by our recovery and determination results. The calibration curves for the oil samples should not be obtained from the derivatization of their methyl ester standards.