A new, direct analytical method using LC-MS/MS for fatty acid esters of 3-chloro-1,2-propanediol (3-MCPD esters) in edible oils

A new, direct analytical method for the determination of 3-chloro-1,2-propanediol fatty acid esters (3-MCPD esters) was developed. The targeted 3-MCPD esters included five types of monoester and 20 types of diester. Samples (oils and fats) were dissolved in a mixture of tert-butyl methyl ether and ethyl acetate (4:1), purified using two solid-phase extraction (SPE) cartridges (C18 and silica), then analysed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Five monoesters and five diesters with the same fatty acid group could be separated and quantified. Pairs of 3-MCPD diesters carrying the same two different fatty acid groups, but at reversed positions (sn-1 and sn-2), could not be separated and so were expressed as a sum of both compounds. The limits of quantification (LOQs) were estimated to be between 0.02 to 0.08?mg?kg-1, depending on the types of 3-MCPD ester. Repeatability expressed as relative standard deviation (RSDr%) varied from 5.5% to 25.5%. The new method was shown to be applicable to various commercial edible oils and showed levels of 3-MCPD esters varying from 0.58 to 25.35?mg?kg-1. The levels of mono- and diesters ranged from 0.10 to 0.69?mg?kg-1 and from 0.06 to 16?mg?kg-1, respectively.