Determination of process contaminants 2- and 3-MCPD esters and glycidyl esters in palm-based glycerol by indirect analysis using GC-MS

Abstract

Esters of 2- and 3-monochloropropanediol (2-MCPDE, 3-MCPDE) and glycidol (GE) are regarded as process contaminants that are found in refined vegetable oils and oil-based foods. Since glycerol is produced during fat splitting, saponification and biodiesel production, it is important to have methods for determining contaminants that might be formed during these processes. Due to the use of glycerol as a food additive, data on the presence of compounds of toxicological concern, including 3-MCPD, are of interest. This study focuses on modifying the indirect analysis of 2-MCPDE, 3-MCPDE and GE using GC-MS based on the AOCS Official Method Cd 29a-13, validating the modified method, and quantifying 2-MCPDE, 3-MCPDE and GE in glycerol. The AOCS Cd 29a-13 method was modified at the initial stage of sample preparation in which the targeted esters were extracted from glycerol by vortex-assisted extraction before sample analysis. This modification was performed based on the polarity of all compounds involved. The calibration functions for all analytes were fitted to linear regression with R² above 0.99. Limits of detection (LOD) 0.02, 0.01 and 0.02 mg kg⁻¹ were obtained for 2-MCPDE, 3-MCPDE and GE, respectively. Spiked glycerol with 3-MCPDE and 2-MCPDE (0.25, 0.51 and 1.01 mg kg⁻¹) and GE (0.58, 1.16 and 2.32 mg kg⁻¹) were used for recovery and precision measurements. Recoveries of 100-108%, 101-103%, and 93-99% were obtained for 2-MCPDE, 3-MCPDE and GE, respectively. Acceptable precision levels with relative standard deviations ranged from 3.3% to 8.3% were obtained for repeatability and intermediate precision. The validated method was successfully applied for the analysis of the target compounds in refined glycerol from commercial plants, which showed that 2-MCPDE, 3-MCPDE and GE levels in the analysed samples were below the detection limit.

Keywords:

• 2-monochloropropanediol ester
• 3-monochloropropanediol ester
• glycidyl ester
• glycerol
• GC-MS

Acknowledgements

The authors would like to thank the Director General of MPOB for permission to publish this article. Appreciation also goes to Khomsatun Telepok, Abd Halim Abd Jalal, Nurliyana Syafiqah Senen, Abdul Niefaizal Abdul Hammid, Mohd Noor Petrus, Ung Yee Wei, Gan Yen Shing, and Tong Kim Suan for their technical assistance in completing this study, and the Malaysian Oleochemical Manufacturers Group (MOMG) for providing the glycerol samples.

Disclosure statement

No potential conflict of interest was reported by the author(s).