Gas chromatographic determination of synthetic antioxidants in edible fats and oils - A simple methylation method

A simple method was developed for determining the antioxidants, BHA, BHT and TBHQ in commercial edible fats and oils. In 2-3 drops (about 60-80 mg) of an oil sample, 10% tetramethylammonium hydroxide (TMAH) methanol solution 1 mL was added and vortex- mixed for 10-minute methylation. The mixture was then extracted with 4-6 mL ether, 0.2% tetradecanol (C-14-OH) 50 muL was added and thoroughly mixed. An aliquot of 0.3 muL of the ether layer was then injected to GC for BHA, BHT and TBHQ analyses. The recoveries from commercial oils were in a range of 94-106%, with a coefficient of variation < 9%. Eighteen commercial edible fat and oil samples of olive, sunflower, peanut, soybean, vegetable and blend oils were analyzed using the developed method. The contents of BHA, BHT and TBHQ were found to be 0-50, 0-267 and 0-37 <mu>g/g. Fourteen out of 18 samples were detected to contain antioxidants. The total antioxidant contents in the three blend oils ran,aed 259-294 mug/g, which exceeded the Chinese National Standards (CNS) control level of 200 mug/g for edible oils.