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High-performance liquid chromatography (HPLC) enantioseparation of terazosin (TER) was accomplished on the immobilised-type Chiralpak IC chiral stationary phase (CSP) under both polar organic and reversed-phase modes. A simple analytical method was validated using a mixture of methanol–water–DEA 95:5:0.1 (v/v/v) as a mobile phase. Under reversed-phase conditions good linearities were obtained over the concentration range 8.76–26.28 μg mL −1 for both enantiomers. The limits of detection and quantification were 10 and 30 ng mL −1 , respectively. The intra- and inter-day assay precision was less than 1.66% (RSD%). The optimised conditions also allowed to resolve chiral and achiral impurities from the enantiomers of TER. The proposed HPLC method supports pharmacological studies on the biological effects of the both forms of TER and analytical investigations of potential drug formulations based on a single enantiomer. At the semipreparative scale, 5.3 mg of racemic sample were resolved with elution times less than 12 min using a mobile phase consisting of methanol–DEA 100:0.1 (v/v) and both enantiomers were isolated with a purity of ≥99% enantiomeric excess (ee). The absolute configuration of TER enantiomers was assigned by comparison of the measured specific rotations with those reported in the literature.

High-performance liquid chromatography (HPLC) was employed for the separation and determination of becliconazole, an imidazole derivative with antifungal activity containing a stereogenic centre, and its impurities. Chiral columns, containing carbamate of cellulose and amylose, were used. The effects of the organic modifiers, ethanol and 2-propanol, in the mobile phase, were studied. The HPLC method gave good performances from qualitative and quantitative standpoints, allowing the enantiomeric ratio of becliconazole and its impurities to be determined. The assay showed linearity over the range 400–4000 ng ml −1 for the impurities and 400–4000 μg ml −1 for becliconazole.

An accurate and reproducible high-performance liquid chromatographic (HPLC) method has been developed and validated for the direct separation of individual enantiomers of lansoprazole, a potent proton pump inhibitor belonging to the family of the substituted benzimidazoles. The enantiomers were resolved on a Chiralpak IA by using a mobile phase consisting of methyl-tert-butyl ether (MtBE)-ethyl acetate (EA)-ethanol (EtOH)-diethylamine (DEA) in the ratio 60:40:5:0.1 (v/v/v/v). Baseline separation of the enantiomers of lansoprazole was obtained with a resolution factor of 8.14. The standard curves for the two enantiomers were linear (r(2)>0.999) in the concentration range of 10-80microg/ml with a working concentration of about 60microg/ml for each enantiomer. Apparent recovery was 100.8% with a relative standard deviation less than 2%. The limit of quantization for each enantiomer of lansoprazole was 0.22microg/ml. The intra-day precisions were in the range of 0.21-0.36 and 0.59-0.66 while the inter-day precisions were in the range of 0.55-1.24 and 0.66-1.19% in terms of retention times and area response RSD% for (R)-(+)- and (S)-(-)-lansoprazole, respectively. The method was also able to resolve impurities from the enantiomers of lansoprazole.

The direct HPLC enantioseparation of Mianserin and a series of aptazepine derivatives is accomplished on polysaccharide-based chiral stationary phases (CSPs). The resolutions are performed on the coated-type Chiralcel OD and Chiralpak AD CSPs and on the first commercially available immobilized-type Chiralpak IA CSP, in normal-phase and polar-organic modes. The complete separation of enantiomers of all racemates investigated was successfully achieved under at least one of CSP/eluent combinations employed. Pure alcohols such ethanol or 2-propanol, with a fixed percentage of DEA added, serve as valuable alternatives to the more common n-hexane-based normal-phase eluents in resolution of Mianserin on the AD CSP. In order to study the chiroptical properties of aptazepine derivatives, chromatographic resolutions are carried out at semipreparative scale using Chiralpak AD and Chiralpak IA as CSPs. Nonconventional dichloromethane-based eluents have permitted to expand the chiral resolving ability of the immobilized Chiralpak IA CSP and to perform mg-scale enantioseparations with an analytical-size column. Assignment of the absolute configuration of the separated enantiomers is empirically established by comparing their chiroptical data with those of structurally related Mianserin. Chirality, 2006. © 2006 Wiley-Liss, Inc.

The HPLC enantiomer separation of a novel series of C5-chiral 1-acetyl-3-(4-hydroxy- and 2,4-dihydroxyphenyl)-5-phenyl-4,5-dihydro-(1H)-pyrazole derivatives, with inhibitory activity against monoamine oxidases (MAO) type A and B, was accomplished using polysaccharide-based chiral stationary phases (CSPs: Chiralpak AD, Chiralcel OD, and Chiralcel OJ). Pure alcohols, such as ethanol and 2-propanol, and typical normal-phase binary mixtures, such as n-hexane and alcohol modifier, were used as mobile phases. Single enantiomers of several analytes examinated were isolated on a semipreparative scale, and their chiroptical properties were measured. The assignment of the absolute configuration was established for one compound by single-crystal X-ray diffraction method and for the other three by CD spectroscopy. The inhibitory activity against MAO of racemic samples and single enantiomers were evaluated in vitro. Chirality 16:625–636, 2004. © 2004 Wiley-Liss, Inc.

A stereospecific high-performance liquid chromatography method for the determination of trans-(-)-paroxetine and its enantiomer in bulk raw material and pharmaceutical formulations was developed and validated. The enantiomeric separation was achieved, without any derivatization, on a carbamate derivative-based column (Chiralpak AD). The effect of the organic modifiers, 2-propanol and ethanol, in the mobile phases was optimised to obtain enantiomeric separation. Limits of detection and quantitation of 2 and 6 ng, respectively, were obtained for both of the enantiomers. The linearity was established in the range of 5-41 microg for trans-(-)-paroxetine and in the range of 10-160 ng for trans-(+)-paroxetine. The accuracy of the method was 102.3% (mean value) for trans-(-)-paroxetine and 99.9% (mean value) for trans-(+)-paroxetine. For the precision (repeatability), a relative standard deviation value of 1.5% (mean value) for trans-(-)-paroxetine and of 2.1% (mean value) for trans-(+)-paroxetine was found. The method is capable of determining a minimum limit of 0.2% of trans-(+)-isomer in commercial samples.