Leo Zanitti

Direct HPLC enantioseparation of omeprazole and its chiral impurities: Application to the determination of enantiomeric purity of esomeprazole magnesium trihydrate

Analytical and semipreparative high-performance liquid chromatography (HPLC) enantioseparation of the proton-pump inhibitor omeprazole (OME) and its potential organic chiral impurities were accomplished on the immobilised-type Chiralpak IA chiral stationary phase (CSP) under both polar organic and normal-phase conditions. The (S)-enantiomers were isolated with a purity of >99% ee and their absolute configuration was empirically assigned by circular dichroism (CD) spectroscopy. A chemo- and enantioselective HPLC method was validated to control the enantiomeric purity of the (S)-enantiomer of OME (ESO), an active ingredient contained in drug products, in the presence of chiral and achiral related substances. The precision, linearity and accuracy of the determination of the (R)-impurity as well as the recovery of ESO from a pharmaceutical preparation were determined. The proposed method uses the mixture methyl tert-butylether (MtBE)-ethyl acetate (EA)-ethanol (EtOH)-diethylamine (DEA) 60:40:5:0.1 (v/v/v/v) as a mobile phase. In these conditions, linearity over the concentration range 0.5-25 microg/ml for (R)-enantiomer was obtained. The limits of detection and quantification were 99 and 333 ng/ml, respectively. The intra and inter-day assay precision was less than 2% (RSD%).

Direct high-performance liquid chromatography enantioseparation of terazosin on an immobilised polysaccharide-based chiral stationary phase under polar organic and reversed-phase conditions.

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 microg 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 > or = 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.

Development and validation of an enantioselective and chemoselective HPLC method using a Chiralpak IA column to simultaneously quantify (R)-(+)- and (S)-(−)-lansoprazole enantiomers and related impurities

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.

Direct separation of the enantiomers of oxaliplatin on a cellulose-based chiral stationary phase in hydrophilic interaction liquid chromatography mode

(R,R)-oxaliplatin is an anticancer enantiopure active pharmaceutical ingredient. Little attention has been devoted to the analysis of its enantiomeric composition. The enantioselective HPLC method reported in the current Pharmacopoeias shows clear disadvantages with regard to the low resolution and long elution times. In this work, it has been proven the applicability of a last generation polysaccharide-based chiral stationary phase (CSP), i.e. the Chiralpak IC-3, in the enantioseparation of oxaliplatin. Experimental results demonstrated the benefits arising from the development of enantioselective hydrophilic interaction liquid chromatography (HILIC) based strategies. A baseline separation with resolution factor of 5.8 was achieved using a 100mm×4.6mm I.D. IC-3 column set at the temperature of 40°C and a mobile phase consisting of acetonitrile-water 100:5 mixture. At a flow rate of 1mLmin(-1) the separation was completed within 8min. The optimized method was proven to be sensitive with LOD and LOQ of the enantiomeric impurity of 0.07 and 0.21μgmL(-1), respectively.

Enantioselective liquid chromatography of C3-chiral 2,3-dihydro-1,2,5-benzothiadiazepin-4(5H)-one and thione 1,1-dioxides on polyacrylamide- and polysaccharide-based chiral stationary phases.

Optically active synthetic and semisynthetic polymers were utilized as chiral stationary phases (CSPs) for the direct chromatographic enantioseparation of a series of 8-chloro-2,3-dihydro-3-methyl-1,2,5-benzothiadiazepin-4(5H)-one and thione 1,1-dioxide. Evaluation of stereochemical integrity of chiral analytes was assessed by enantioselective temperature and flow-dependent HPLC. A stopped-flow high-performance liquid chromatography (sfHPLC) procedure was developed for the determination of the rate constants and free energy barriers of enantiomerization of enantiomers of 8-chloro-2-(3-methylbut-2-enyl)-2,3-dihydro-3-methyl-1,2,5-benzothiadiazepin-4(5H)-thione 1,1-dioxide (compound 2) in the presence of Chiraspher and Chiralcel OD CSPs. In order to study the chiroptical properties of the individual enantiomers of analytes investigated, semipreparative chromatographic resolutions were performed. The assignment of the absolute configuration was empirically established by comparing the CD spectra of the separated enantiomers with those obtained from structural analogues.

Direct resolution of a new antifungal agent, voriconazole (UK-109,496) and its potential impurities, by use of coupled achiral-chiral high-performance liquid chromatography

SummaryCoupled achiral-chiral high-performance liquid chromatography (HPLC) with an achiral amino-based column coupled with a chiral amylose-based column has been used for qualitative and quantitative determination of the potential chiral and achiral impurities of Voriconazole (UK-109,496), a new antifungal agent with two stereogenic centres. The effect of the organic mobile-phase modifier, ethanol, was studied. The assay response was linearly dependent on concentration over the range 1.2–40.4 μg for Voriconazole and 2.5–104.0 ng for the impurities. The limit of detection was 2.5 ng for each analyte.

Retention behavior of proton pump inhibitors using immobilized polysaccharide-derived chiral stationary phases with organic-aqueous mobile phases

In the present study, the chromatographic behavior of two immobilized polysaccharide-derived chiral stationary phases (CSPs), the Chiralpak ID-3 and Chiralpak IE-3, under aqueous mobile phases conditions is presented. Four proton pump inhibitors (PPIs) (omeprazole, lansoprazole, pentaprazole and rabeprazole) were selected as test compounds. The effect of the concentration of water in the mobile phase was investigated with respect to its contribution to enantioselectivity and retention. Under acetonitrile-water mobile phase conditions, retention behavior evidenced an interesting pattern. At lower water content, the retention factors decreased with increasing water and at higher water content a reversed trend was observed. These findings support the hypothesis that two retention mechanisms operated successively on the same CSP: the HILIC (with water-poor eluents) and RPLC (with water-rich eluents) modes. The retention factors were minimum in the intermediate region, corresponding to a water concentration of about 20%. Interestingly, the baseline separation of all PPIs investigated was optimized under organic-aqueous mobile phases containing a high water content (from about 50 to 65%). Thus, the dual retention behavior of the PPIs on the Chiralpak ID-3 and Chiralpak IE-3 made it possible to reach greener and harmless enantioselective conditions in a short analysis time.

Green high-performance liquid chromatography enantioseparation of lansoprazole using a cellulose-based chiral stationary phase under ethanol/water mode.

A simple and environmentally friendly reversed-phase high-performance liquid chromatography method for the separation of the enantiomers of lansoprazole has been developed. The chromatographic resolution was carried out on the cellulose-based Chiralpak IC-3 chiral stationary phase using a green and low-toxicity ethanol-aqueous mode. The effects of water content in the mobile phase and column temperature on the retention of the enantiomers of lansoprazole and its chiral and achiral related substances have been carefully investigated. A mixed-mode hydrophilic interaction liquid chromatography and reversed-phase retention mechanism operating on the IC-3 chiral stationary phase allowed us to achieve simultaneous enantioselective and chemoselective separations in water-rich conditions. The enantiomers of lansoprazole were baseline resolved with a mobile phase consisting of ethanol/water 50:50 without any interference coming from chiral and achiral impurities within 10 min.

Direct resolution of the enantiomers of new diphosphine and diphosphine oxide ligands by high-performance liquid chromatography

SummaryResolution of the enantiomers of new racemic diphosphines, which are very useful ligands for stereoselective catalysts, and of the corresponding phosphine oxides has been investigated by high-performance liquid chromatography (HPLC) on four different chiral stationary phases (CSP)—Chiralpak AD, Whelk-01, and Supelcosil naphthylurea and phenylurea columns. The mobile phases were optimized to achieve separation of the enantiomers. α andRS values ranged from 1.05 to 5.17 and from 0.37 to 6.57, respectively, for the Chiralpak AD and (R,R)-Whelk-01 columns. For the Supelcosil LC-(R)-phenylurea and Supelcosil LC-(S)-naphthylurea columns α values ranged from 1.05 to 1.62 andRS from 0.35 to 3.61.

Comparison of reversed-phase enantioselective HPLC methods for determining the enantiomeric purity of (S)-omeprazole in the presence of its related substances ☆

A simple analytical high-performance liquid chromatography (HPLC) method was applied for the enantiomeric excess determination of esomeprazole ((S)-OME), the enantiopure active ingredient contained in drug products, in the presence of its potential organic impurities A-E. The enantioselective separation was accomplished on the immobilized-type Chiralpak ID-3 chiral stationary phase (CSP) under reversed-phase conditions. The results were evaluated and compared with those obtained by the official enantioselective method of European Pharmacopoeia used as the reference for checking the enantiomeric excess of (S)-OME. It has been established that the use of the Chiralpak ID-3 CSP allows the determination of the enantiomeric purity of (S)-OME without any interference coming from its chiral and achiral related substances. The analytical procedure of the drug regulatory agencies based on the AGP CSP suffered instead from poor specificity due to overlap of the peaks pertinent to the achiral impurity A and the chiral impurity (R)-OME (impurity F).