2016 Volume 16 Issue 4 Pages 173-182
Fatty acid esters of monochloropropanediols (MCPDs) and glycidol are undesirable contaminants in oil processing. The amount of 3-MCPD, glycidol, and their esters are indirectly measured by DGF standard method C-VI 18 (10), assay A and B, respectively. In the course of the method, 3-MCPD and glycidyl ester can be converted each other by basic and following acidic treatment. This bidirectional conversion accounting for incorrect quantification is discussed and identified in this research. Direct measurement using 1H- and 13C-NMR clearly revealed that 3-MCPD was converted into glycidol by basic conditions in the transesterification step, and then the almost same amount of generated glycidol was re-converted into that of 3-MCPD by acidic treatment in the derivatization (neutralization) step, resulting that quantification result became apparently reasonable.
Regioisomer of 3-MCPD, 2-MCPD, was synthesized in >99% purity, identified, and first quantified by DGF standard method C-VI 18 (10). 2-MCPD as well as 3-MCPD was also converted into glycidol in the transesterification step, and was re-converted into 2-MCPD in the derivatization step.
In this short review, the author explains influence of bidirectional conversion MCPDs into glycidol in the course of DGF standard methods compared with the other indirect methods on the quantification. Furthermore, 2-MCPD quantification without pure 2-MCPD as a standard and 2-MCPD-d5 as an internal standard is also explained in detail.
