Circular dichroism spectra of cyclodextrins–ketoprofen inclusion complexes: Determination of enantiomeric purity Original Research Article

The formation of inclusion complexes among various cyclodextrins (viz. α, β, γ, trimethyl-β- and hydroxypropyl-β-cyclodextrin) and the S(+) and R(−) enantiomers of ketoprofen was studied by using the circular dichroism (CD) technique. All the cyclodextrins studied, except α-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 β-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.