Direct analysis of intact glycidyl fatty acid esters in edible oils using gas chromatography–mass spectrometry

• A GC–MS method for the analysis of intact glycidyl esters in edible oils and fats was developed.
• It is the first method which uses standard GC–MS equipment widely available in analytical laboratories for oil and fat analysis.
• Method sensitivity is an order of magnitude higher than those of the AOCS official method.
• Quantitative GC–MS results are in good agreement with results obtained by two other methods.
• Method reliability, accuracy and ruggedness are excellent allowing continuous use of the method for more than 7 months with over 400 samples being analyzed.

Glycidyl esters (GE), fatty acid esters of glycidol, are process contaminants formed during edible oil processing. A novel direct method for the determination of intact GE in oils and fats based on gas chromatography–mass spectrometry (GC–MS) is presented. The method consists of a simple extraction step of GE from the lipid matrix, purification of the extract and isolation of GE by normal phase liquid chromatography (NPLC). Individual GE in the final fraction are separated and quantified by standard GC–MS operated in selected ion monitoring (SIM) mode. The setup and conditions of the GC–MS were optimized in such a way that thermal degradation of GE and artifact formation were prevented. The method exhibits very good performance parameters: the limit of detection was approximately 0.01 mg/kg for the individual GE (corresponding to 0.002–0.003 mg/kg of free glycidol), the repeatability was in the range of 5–12% for individual GE at levels above 0.1 mg/kg, and recovery values ranged from 85 to 115% depending on the level and the chain identity of the GE. The comparison of experimental values with spiked levels and with the results obtained by other methods confirmed a good trueness. Over a period of several months of extensive use the method was found to be very reliable and rugged.