SIMULTANEOUS DETERMINATION OF STEROLS IN EDIBLE OILS BY USE OF A CONTINUOUS SEPARATION MODULE COUPLED TO A GAS-CHROMATOGRAPH

A new analytical method that combines on-line isolation-preconcentration, extraction and gas-liquid chromatography was developed for the determination of sterols in oils and fats. A silica gel column permits the isolation of sterols together with triglycerides (25%) which were further transesterified with acetyl chloride-methanol to fatty acid methyl esters. The proposed method was applied to the determination of cholesterol, campesterol, p-sitosterol and stigmasterol in vegetable oils and lard; olive oil was also mixed with sunflower-seed oil and lard in order to check for potential adulteration of vegetable oils. The average recoveries of sterols added to olive oil at concentrations between 13.6 and 40.8 mg per 100 g of oil ranged from 91.4 to 103.9%.