Enantioselective separation of polychlorinated biphenyl atropisomers using chiral high-performance liquid chromatography

Permethylated beta-cyclodextrin derivatized silica was used as the chiral stationary phase in reversed-phase HPLC to separate the atropisomers of polychlorinated biphenyls (PCBs). The retention behaviour of 26 atropisomers was studied under optimum chromatographic conditions. Thirteen atropisomers could be completely resolved and six were partially separated. Among the atropisomers separated 14 are of environmental relevance since they do not enantiomerize at physiological temperatures. A retention behaviour study showed that tri-ortho PCBs, which lack ''buttressing'' chlorine substituents in the 3'-position, are difficult to separate. The best resolution was obtained for PCBs with 2,3,6-substitution in the less substituted biphenyl ring.