Abstract
The objective of this study was to establish a method for detecting fatty acid esters of chloropropanols [including 2-monochloropropane-1,3-diol (2-MCPD) ester and 3-monochloropropane-1,2-diol (3-MCPD) ester] in infant milk powder using isotope dilution and GC-MS. The fat fraction in infant milk powder samples was extracted and treated with sodium methylate–methanol to cleave the ester bonds of the 2- and 3-MCPD esters. The resultant 2- and 3-MCPDs in the samples were purified with matrix solid-phase liquid–liquid extraction and derivatized with heptafluorobutyryl imidazole for GC-MS analysis. Standard samples of deuterium isotope–labeled 2- and 3-MCPD palmitic acid double esters and stearic acid double esters were used as the internal standards. We also detected 2- and 3-MCPD ester contents in 88 commercial samples of infant formula milk powder using this system. The detection system we established showed a good linearity of 2- and 3-MCPD ester contents in serially diluted standard solutions within the concentration range 25−1000 μg/L, with r2 > 0.9995 and an LOD of 30 μg/kg for both of the MCPD esters. The recoveries of the two MCPD esters spiked at 25, 50, 100, and 200 μg/kg in blank infant formula milk ranged from 98.2 to 110.5%, with RSDs <4.8%, suggesting good accuracy and reliability of this method. In the 88 commercial infant formula milk powder samples, the mean content of 2-MCPD ester was 41 μg/kg (0–52 μg/kg) and that of 3-MCPD was 185 μg/kg (0–316 μg/kg). Based on these results, we estimated the exposure levels of the two MCPD esters in infants fed on formula milk, and the results indicate potential health risks of consuming formula milk products contaminated by the two MCPD esters.
