LIQUID-CHROMATOGRAPHIC METHOD FOR DETERMINING THE PERCENT OF OLESTRA IN LIPID SAMPLES

A liquid chromatographic (LC) method has been developed to determine t he percent of olestra in lipid samples. To achieve the highest degree of accuracy, this method requires the use of an olestra standard with the same molecular composition as the olestra in the lipid sample to b e analyzed. Samples were analyzed by reversed-phase LC using an evapor ative light-scattering detector. Chromatography was performed with a 5 mum octadecylsilane-Zorbax column that separates olestra from other l ipophilic components. Three types of olestra standards (soybean-oil ol estra, unheated cottonseed-oil olestra, and heated cottonseed-oil oles tra), each analyzed in soybean oil, showed linearity when the amount o f olestra injected ranged from 20 to 160 mug (r = 0.9996). The area un der the olestra peak (retention time 3.5 to 4.9 min) was used to quant ify the amount of olestra in olestra-lipid samples, by comparing the o lestra area for the sample with that of the standard using a curve der ived by linear regression. The method was evaluated using 3 types of o lestra blended with soybean oil and varying the percent of olestra in the olestra-lipid blend from 5 to 90%. Recovery of olestra from these olestra-lipid blends varied from 99.2 to 106.0%, demonstrating excelle nt accuracy, with method precision expressed as the coefficient of var iation, 0.9%. Each error estimate was derived from 5 parallel determin ations. With proper validation (e.g., running an olestra-free blank fo r each lipid matrix), this method provides a rapid, accurate, and prec ise technique for measuring the percent of olestra in lipids extracted from olestra-formulated foods and in olestra-lipid blends.