ABSTRACT
The contents of cholesterol in a number of vegetable oils were determined by saponification-gas chromatography ( FID) . There was quite a large possibility that cholesterol peak was seriously interfered by saponification-gas chromatography ( FID) , so it was difficult to set a cholesterol content value to differentiate vegetable oil from waste oil. Solid phase extraction ( SPE) sample pretreatment was chosen and the process conditions were optimized. The optimal conditions were as follows:0. 25 g of oil samples, 20 mL of 0. 6%ethyl ether-hexane ( V/V) as eluent ( get rid of fatty acid glycerides) and 20 mL of 15% ethyl ether-hexane ( V/V) as eluent ( obtain cholesterol) . An obvious cholesterol-content-difference between vegetable oils and waste oils was found by SPE-GC. The detected cholesterol contents in 84 vegetable oil samples were all less than 50 μg/g and the contents of 11 waste oil samples among the 13 waste oils were greater than 50 μg/g. Therefore, cholesterol content in vegetable oil of more than 50 μg/g could be determined as suspected waste oil, not vice versa by SPE-GC. The correlation coefficient R2 was 0. 9999 in 0-760 mg/L concentration range, and the detection limit was 6. 0 μg/g. Relative standard deviations at two concentration levels of 17. 7 and 695 mg/L were 1. 6% and 1. 5% respectively. The recovery was 103%.