Chiral separations of underivatized arylpropionic acids by capillary zone electrophoresis with various cyclodextrins - Acidity and inclusion constant determinations

Chiral separations of non-steroidal anti-inflammatory drugs of the family of arylpropionics acids (carprofen, flurbiprofen, indoprofen, ketoprofen, naproxen, pranoprofen and suprofen) were studied by capillary electrophoresis in different pH buffers (pH 4, 6, 8 and 10) containing various neutral cyclodextrins (CDs) (beta-CD, hydroxypropyl-beta-CD, dimethyl-beta-CD, trimethyl-beta-CD and hydroxypropyl-gamma-CD). Baseline resolution of all the racemates was only achieved with trimethyl-beta-CD at pH 4.0. The solute acidity constants and apparent formation constants of their inclusion complexes were also derived from these experiments as an aid for understanding chiral recognition and selectivity optimization. It is clearly shown that no conclusion with regard to the stereoselectivity of a CD can be drawn from the strength of the fit between the CD and the enantiomers.