Abstract:

A fast analytical method for five common fatty acids in six edible vegetable oils was developed by ultra-performance convergence chromatography-mass spectrometry (UPC²-MS). The five fatty acids are palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. Their contents in the corn oil, sunflower oil, soybean oil, tea oil, rapeseed oil and peanut oil were compared. The chromatographic separation was performed on an ACQUITY UPC² BEH 2-EP column (100 mm×2.1 mm, 1.7 μm) using the mobile phases of carbon dioxide and methanol/acetonitrile (1:1, v/v) with gradient elution. The separated compounds were detected by negative electrospray ionization ESI^--MS. The results showed that the reasonable linearities were achieved for all the analytes over the range of 0.5-100 mg/L with the correlation coefficients (R²) of 0.9985-0.9998. The limits of quantification(S/N≥10)of the five fatty acids were 0.15-0.50 mg/L. The recoveries of the five fatty acids at three spiked levels were in the range of 89.61%-108.50% with relative standard deviations of 0.69%-3.01%. The developed method showed high performance, good resolution and fast analysis for the underivatized fatty acids. It has been successfully used to detect the five fatty acids from corn oil, sunflower oil, soybean oil, tea oil, rapeseed oil and peanut oil.

Key words: edible vegetable oils, fatty acids, ultra-performance convergence chromatography-mass spectrometry(UPC²-MS), underivatization