Generalized Method to Quantify Glycidol Fatty Acid Esters in Edible Oils

We previously reported a method to quantify five species of glycidol fatty acid esters (GEs) in edible oils which used a combination of a double solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS) using fast HPLC. To expand its application, we established a new method using conventional HPLC, which is applicable not only to liquid oils but also to solid ones. The optimized LC-MS conditions using conventional HPLC were useful for standard GEs but not for oil samples because of the insufficient accuracy during sequential runs. Thin-layer chromatographic studies revealed that co-existing diacylglycerols were not sufficiently removed by the original SPE procedure due to excessive amounts of oil applied to the normal-phase SPE, which disturbed the quantitative and stable detection only when conventional HPLC was employed. The amount of oil applied was decreased tenfold (100 mg → 10 mg), which resulted in stable LC-MS measurements. Furthermore, the use of chloroform/acetone, instead of acetonitrile, prior to the SPE treatment expanded its applicability to solid oils, with recovery values ranging from 102.7 to 109.5% for three oil samples (two liquid and one solid oils). This method can form the basis of a standardized method for the quality control of GEs in edible oils.