Analytical method for the determination of 2- and 3-monochloropropanediol esters and glycidyl ester in palm-based fatty acids by GC-MS

Abstract

The 2- and 3-monochloropropanediol esters (2-MCPDE, 3-MCPDE) and glycidyl ester (GE) are process contaminants that can form in vegetable oils during the refining process. In addition, it is likely that fatty acids produced from oil splitting process possessed such contaminants which may be formed during the refining process. This study reports on the modification of AOCS Official Method Cd 29a-13 to suit the nature of fatty acids, method validation, and quantification of 2-MCPDE, 3-MCPDE and GE in commercial fatty acids (i.e. caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid). The sample preparation step was modified during the extraction of 2-MCPDE, 3-MCPDE, and 3-MBPDE from the aqueous phase, through the addition of tetrahydrofuran to facilitate the extraction process. The calibration curves constructed for 2-MCPDE, 3-MCPDE and GE showed good linearity with coefficient of correlation (R2) > 0.999. The attained limit of detection (LOD) was 0.02, 0.01 and 0.03 mg kg−1 for 2-MCPDE, 3-MCPDE, and GE, respectively. Recovery, repeatability and intermediate precision were then evaluated using spiked fatty acids at three levels of 2-MCPDE, 3-MCPDE, and GE. Satisfactory recoveries were achieved, ranging from 100.6 to 108.4%, 96.8–100.9%, and 99.5–103.0% for 2-MCPDE, 3-MCPDE, and GE, respectively. Repeatability and intermediate precision (expressed as relative standard deviation) were less than 9%, 7%, and 6% for 2-MCPDE, 3-MCPDE, and GE, respectively. Analyses conducted on various commercial fatty acids from oleochemical plants showed that 2-MCPDE, 3-MCPDE and GE were lesser than the LOD of the respective compounds. The establishment of this method enables for routine monitoring of 2-MCPDE, 3-MCPDE, and GE in fatty acids.