Circular dichroism spectra of cyclodextrins-ketoprofen inclusion complexes -: Determination of enantiomeric purity

The formation of inclusion complexes among various cyclodextrins (viz. alpha, beta, gamma, trimethyl-beta- and hydroxypropyl-beta-cyclodextrin) and the S(+) and R(-) enantiomers of ketoprofen was studied by using the circular dichroism (CD) technique. All the cyclodextrins studied, except alpha-cyclodextrin, introduce marked differences between the CD spectra for the S(+) and R(-) enantiomer. A new method for determining the enantiomeric purity in mixtures of both ketoprofen enantiomers based on the use of beta-cyclodextrin as chiral selector and partial least-squares regression (PLSR) for calibration is proposed. The method provides relative standard errors (RSE) of calibration and prediction of the order of 2%. It was also applied to the determination of the enantiomeric excess of eutomer S(+) in the presence of distomer R(-) contents below 5%. The good results provided by the proposed method and its analytical expeditiousness make it a competitive alternative to chromatographic methods for the same purpose. (C) 2000 Elsevier Science B.V. All rights reserved.