Determination of glycidyl esters and 3-MCPD esters in edible oils by sample pretreatment with the combination of lipase hydrolysis and modified QuEChERS for GC-MS analysis

Glycidyl esters (GEs) and 3-chloroprapane-1,2-diol esters (3-MCPDEs) are processing contaminants in refined edible oils that have raised concerns globally owing to their potentially carcinogenic properties. Official analytical methods for GEs and 3-MCPDEs, such as AOCS Cd 29a-13 and AOCS Cd 29b-13, require up to 16 h for chemical hydrolysis. Also, parallel experiments should be conducted to correct for the conversion of analytes during hydrolysis in AOCS Cd 29b-13. For AOCS Cd 29c-13 with the shortest operating time, the reaction time (3.5–5.5 min) and temperature of alkaline hydrolysis should be carefully controlled, implying the accuracy may be influenced by human errors. Here, we propose a novel method based on Candida rugosa lipase hydrolysis and direct detection of free form GEs, glycidol, which was achieved by sample preparation with modified QuEChERS, to prevent side reactions in previous approaches, and also to shorten the overall sample preparation time. Glycidol was directly analyzed without halogenation and derivatization, whereas 3-MCPD required derivatization for analysis by GC-MS. Our method showed good accuracy and precision in terms of repeatability, intermediate precision, and reproducibility (inter-laboratory precision). The limit of detection (LOD) and limit of quantification (LOQ) for glycidol were 0.02 and 0.1 mg/kg, which is sufficient for practical applications. The proposed method was further compared with AOCS Cd 29c-13 by determination of GEs content in commercial oil samples and spiked samples. Our method with a streamlined procedure seems to possess potential advantage of reduced errors from operational factors. This proposed method based on direct detection of glycidol may serve as a simplified alternative for routine analysis of GEs and 3-MCPDEs in edible oils.