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.

Cyclodextrins (CDs), which are produced from starch, are a class of cyclic oligosaccharides consisting of several α-(1,4)-linked D-glucose units. They have a cavity of sub-nanometer size, into which a guest molecule of the appropriate size and shape can be selectively incorporated. The ability of CDs to form inclusion complexes with guest molecules has been studied academically, and applications in various industrial fields including food, cosmetics, and pharmaceuticals have been developed. However, in most cases, inclusion complex formation with CDs has been limited to aqueous media and several kinds of polar organic media. On the other hand, the effective guest inclusion by CD hosts in nonpolar media has not been achieved yet, because the enormous amounts of nonpolar solvents and oils become a strong competitor for inclusion within the CD cavity. Recently, we found that 6-O-modified β-CDs, such as heptakis(6-O-tert-butyldimethylsilyl)-β-CD and heptakis(6-O-triisopropylsilyl)-β-CD, effectively formed inclusion complexes with polychlorinated aromatic compounds and pyrene in nonpolar solvents. In this review, I describe the inclusion complex formation between 6-O-modified β-CDs and various guest molecules in nonpolar media and the removal and recovery of polychlorinated biphenyls (PCBs) in oil using various CD hosts.