[Enantioseparation of quinazolone derivatives using an AGP-based liquid chromatography stationary phase]. / Az AGP-alapú folyadék-kromatográfiás állófázis alkalmazása kinazolon származékok enantiomerjeinek elválasztásában.

An AGP-based chiral stationary phase has been applied successfully for enantioseparation of 4(3H)-quinazolone derivatives. Chiral-AGP is proved to be an excellent selector, as optimized chromatographic conditions allow with one exception baseline resolution for the enantiomers of the potential cholecystokinin antagonist compounds (alpha = 1.19-1.85). Retention and enantioselectivity could be modified to a large extent by varying the eluent pH and adding organic solvents with different types i.e. acetonitrile and 2-propanol to the buffered mobile phase. It was established that by increasing the eluent pH from 6.0 to 7.0 the retention factors of of the model compounds bearing no protonable groups are increased in the presence of 7 v/v % (1.33 M) acetonitrile. However further increasing the acetonitrile content up to 10 v/v % or addition of 2-propanol in equimolar concentration (1.33 M) no similar changes could be detected with the same modification in the eluent pH. These observations are explained by changes in the sorption properties of the selector determined simultaneously by the type and concentration of organic modifier and also the eluent pH. The experimental data give further insight into the chromatographic mechanism on a Chiral-AGP column.

[Investigation of the sorption properties and pharmaceutical application of alpha1-acid glycoprotein by liquid chromatography]. / Az alpha 1-savas glikoprotein szorpciós tulajdonságainak folyadék-kromatográfiás vizsgálata és gyógyszeranalitikai alkalmazása.

The separation and quantitation of the enantiomers and also the determination of the enantiomeric purity are all current and indispensable tasks for the pharmaceutical analysis. The aim of this work was to study the sorption properties of the alpha 1-acid glycoprotein (AGP) based stationary phase, which may have crucial importance for the enantioselectivity. New binding data are presented for the mechanism of the chromatographic separation, which has not clarified in the literature yet. On the basis of these new findings the composition of the mobile phase for a given analytical separation can be designed, including the preparative separation, as well. Binding data for dioxane, known as a solvent with low dielectric constant, are determined at first time. It was found that the sorption of both acetonitrile and dioxane is pH-dependent: as at pH 7.2 the binding can be characterized by a saturation curve, while at pH 4.0 by a twostep, monotone curve. The pH-dependence of the adsorption has been explained by conformational changes of the selector, which were confirmed by CD-spectroscopic and fluorescence quenching study of the native AGP. In accordance with the binding study by increasing the acetonitrile percentage at pH 4.0 a tipical alpha-helical peak was observed in the CD-spectrum. Opposite that at pH 7.2 the increase in the acetonitrile content does not result in any changes in the spectra. Effective dynamic quenching constants of AGP have been determined at given acetonitrile concentrations using 2,2,2-trichloroethanol as fluorescence quencher. In agreement with the results of the CD measurements at pH 4.0 it was found that the degree of quenching enhanced by increasing the amount of the acetonitrile, that can be explained by enhanced exposure of the buried tryptophan residues. Taking these results into account, new optimized and validated HPLC methods have been developed for compendial control in testing the enantiomeric purity of an acidic (ibuprophen), a basic (propranolol) and a neutral (norgestrel) drug molecule.