Rapid and sensitive determination of fatty acids in edible oil by liquid chromatography-electrospray ionization tandem mass spectrometry

A sensitive and robust on-line LC/MS method was developed for quantitative determination of linoleic acid, docosahexaenoic acid and docosanoic acid from edible oil samples. The oil samples were dissolved in chloroform-isopropyl alcohol (20:80, v:v) solution and the three fatty acids were separated by HPLC with a C4 column using 10 mmol/L ammonium acetate-isopropyl alcohol-acetonitrile (20:40:40, v:v:v) mobile phase in isocratic elution. Electrospray ionization mass spectrometry with the selected ion recording monitoring was used to detect and quantify the fatty acid. The calibration curves were linear in the range of 10.00-5000 pg/mL for linoleic acid and docosanoic acid, and 1.000-500.0 pg/mL for docosahexaenoic acid. The limit of detection was 2.0 pg/mL for linoleic acid, 3.0 pg/mL for docosanoic acid, and 0.20 pg/mL for docosahexaenoic acid. The results showed that the method described in this paper could be utilized for rapid determination of three fatty acids at picogram levels in edible oils.