A non-aqueous capillary electrophoretic method developed with quinine and tert.-butyl carbamoylated quinine as chiral selectors for the enantioseparation of N-protected amino acids was applied to the investigation of other quinine derivatives as chiral additives. The optimum composition of the background electrolyte was found to be 12.5 mM ammonia, 100 mM octanoic acid and 10 mM chiral selector in an ethanol-methanol (60:40, v / v) mixture. Under these conditions, a series of chiral acids, as various benzoyl, 3,5-dinitrobenzoyl and 3,5-dinitrobenzyloxycarbonyl amino acid derivatives were investigated with regards to selectand-selector relationships and enantioselectivity employing quinine, quinidine, cinchonine, cinchonidine, tert.-butyl carbamoylated quinine, tert.-butyl carbamoylated quinidine, dinitrophenyl carbamoylated quinine and cyclohexyl carbamoylated quinine as chiral selector.

The aim of the present work was to investigate the separation of nonsteroidal anti‐inflammatory drugs (NSAIDs: niflumic acid, flufenamic acid, piroxicam, alclofenac, tiaprofenic acid, flurbiprofen, suprofen, ketoprofen, naproxen, indomethacin, carprofen, indoprofen, sulindac) in capillary electrophoresis (CE) using completely nonaqueous systems. The influence of different parameters such as nature and proportion of organic solvent (methanol, acetonitrile, 2‐propanol), apparent pH (ranging from 7 to 9) and temperature (ranging from 25 to 40oC) on selectivity and migration times were studied systematically in an uncoated fused‐silica capillary. A nonaqueous electrolyte made of 50 mM ammonium acetate — 13.75 mM ammonia in methanol proved to resolve 11 NSAIDs at 25oC and 13 NSAIDs at 36oC, both within 13 min and without a modifier besides the methanol itself. The same buffer containing 30% acetonitrile provides a satisfactory separation for 13 NSAIDs within 14 min at 25oC.

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A capillary electrophoretic (CE) method for the enantioseparation of N-protected chiral amino acids was developed using quinine and tert-butyl carbamoylated quinine as chiral selectors added to nonaqueous electrolyte solutions (NACE). A series of various N-derivatized amino acids were tested as chiral selectands, and in order to optimize the CE enantioseparation of these compounds, different parameters were investigated: the nature of the organic solvent, the combination of different solvents, the nature and the concentration of the background electrolyte, the selector concentration, the capillary temperature, and the applied voltage. The influence of these factors on the separation of the analyte enantiomers and the electroosmotic flow was studied. Generally, with tert-butyl carbamoylated quinine as chiral selector, better enantioseparations were achieved than with unmodified quinine. Optimum experimental conditions were found with a buffer made of 12.5 mM ammonia, 100 mM octanoic acid, and 10 mM tert-butyl carbamoylated quinine in an ethanol-methanol mixture (60:40 v/v). Under these conditions, DNB-Leu enantiomers could be separated with a selectivity factor (␣) of 1.572 and a resolution (Rs) of 64.3; a plate number (N) of 127,000 and an asymmetry factor (As) of 0.93 were obtained for the first migrating enantiomer. Chirality 11: 622-630, 1999.

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