Columns containing different types of cyclodextrin derivatives have been evaluated for chiral gas chromatographic separation of atropisomeric PCBs, o,p´‐DDT and o,p´‐DDD. Separation was attempted on columns containing mixed chiral selectors, and the performance of two closely related selectors was also examined. The cyclodextrins were: permethylated‐β‐CD (PM‐β‐CD), heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐CD (2,3‐M‐6‐TBDMS‐β‐CD), heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐CD (2,3‐M‐6‐THDMS‐β‐CD), and heptakis(2,3‐di‐O‐ethyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐cyclodextrin (2,3‐E‐6‐THDMS‐β‐CD). The cyclodextrins were dissolved in OV‐1701 or in a dimethylsiloxane/silarylene copolymer containing 5% phenyl in the backbone. The application of mixed chiral selectors led to improved separations, however; at most eleven PCB congeners were separated on a single column. Chiral resolution of o,p´‐DDD was achieved. The use of a dimethylsiloxane/silarylene copolymer as a matrix for the cyclodextrins is a promising approach. With such a matrix, blocking of the CD cavities by silicone substituent groups can be avoided, and a reasonable CD solubility can be provided. The selectivity of heptakis(2,3‐di‐O‐ethyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐CD and heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐hexyldimethylsilyl)‐β‐CD was quite different, the former selector could separate four congeners, while the latter separated ten congeners.

Determination of enantiomeric purity is most often done under overload conditions, which leads to deformed peaks. In general, the best resolutions are obtained when the small peak appears before the large peak in the electropherogram. To be able to determine the R(+)-impurity in the S(-)-form as well as the S(-)-impurity in the R(+)-form the elution orders have to be reversed. The present paper describes reversal of enantiomeric elution order for the basic analyte propranolol and the acidic analyte ibuprofen. For propranolol, a charged heptakis-(6-sulfo)-beta-cyclodextrin (CD) is used in the background electrolyte. For ibuprofen, a mix of the charged heptakis-(6-sulfo)-beta-CD and the uncharged heptakis-(2,3,6-tri-O-methyl)-beta-CD is used in the background electrolyte. The use of a coated capillary and reversal of the polarity shift the elution order, buffer composition is unchanged in both cases. The enantiomers of propranolol and ibuprofen are well separated on both the coated and uncoated capillaries. Detection limits of enantiomer impurities are investigated using spiked samples of both propranolol and ibuprofen.