Determination of darusentan enantiomers in rat plasma by enantioselective liquid chromatography with tandem mass spectrometry using cellulose-based chiral stationary phase

A sensitive, specific and rapid liquid chromatography-mass spectrometry (LC-MS/MS) method has been developed and validated for enantioselective determination of darusentan enantiomers, orally active potent endothelin-A receptor antagonist, in rat plasma. The plasma samples were pretreated by protein precipitation with methanol and baseline chromatographic separation was performed on a Chiralcel OD-RH column with a mobile phase consisting of acetonitrile/water/formic acid (50:50:0.1, v/v/v) at a flow rate of 0.5 mL/min. The detection was accomplished by multiple-reaction monitoring (MRM) scanning via electrospray ionization (ESI) source operating in the negative ionization mode. The calibration curve was linear over the investigated concentration from 0.500 to 2500 ng/mL (r≥0.995) for each enantiomer using 50 μL of rat plasma. The lower limit of quantitation (LLOQ) for each enantiomer was 0.500 ng/mL. The intra- and inter-day precisions were not more than 10.2% and the accuracy was within the range from -5.4 to 6.3% for darusentan enantiomers. No chiral inversion was observed during the plasma preparation, storage and analysis. The method proved adequate for enantioselective pharmacokinetic studies of darusentan enantiomers after oral administration of three different doses of racemic darusentan.     

Development of enantioselective gas chromatographic quantitation assay for dl-threo-methylphenidate in biological fluids

An enantioselective gas chromatographic quantitation assay was developed for the enantiomers of dl-threo-methylphenidate in plasma and urine. dl-threo-Methylphenidate and the internal standard were acylated with N-heptafluorobutyryl-1-prolylchloride under Schotten-Baumann conditions prior to gas chromatographic separation on achiral mixed stationary phases. The derivatives were detected by means of a nitrogen-phosphorus detector. Linear and reproducible calibration curves were obtained over the concentration ranges 0.43-43.25 and 2.16-216.25 ng/ml enantiomer in plasma or urine, respectively. This enantioselective gas chromatographic quantitation assay was applied in a single oral dose disposition study of dl-threo-methylphenidate in a healthy adult volunteer. Stereoselective differences were observed in the plasma concentration-time profiles and cumulative urinary excretion profiles following oral doses of 20 and 40 mg of dl-threo-methylphenidate hydrochloride. Only d-threo-methylphenidate was detectable in plasma after 4 h.     

LC‐MS/MS determination of cinacalcet enantiomers in rat plasma on Chirobiotic V column in polar ionic mode: application to a pharmacokinetic study

A simple and selective polar ionic liquid chromatography–tandem mass spectrometric method for separation and determination of cinacalcet enantiomers in rat plasma was developed and validated. The chromatographic separation was accomplished on a Chirobiotic V column packed with vancomycin as a chiral stationary phase using 2.5 mm ammonium formate in 100% methanol as a mobile phase in an isocratic mode of elution at a flow rate of 1.0 mL/min. The analytes were extracted from rat plasma by precipitating the proteins with acetonitrile. The developed method exhibited a linear dynamic range over 0.5–500 ng/mL in rat plasma for both enantiomers. The method was successfully applied to study the pharmacokinetics after a single dose by oral administration of 10 mg/kg of cinacalcet enantiomers to healthy male Wistar rats. Copyright © 2014 John Wiley & Sons, Ltd.     

Enantiospecific determination of PNU-83894 and its major metabolite, PNU-83892, in plasma, and its application to the characterization of the enantioselective pharmacokinetics of PNU-83894 in the dog

A chiral method for the simultaneous analysis of the (+)- and (-)-enantiomers of PNU-83894 and its metabolite, PNU-83892, in plasma was developed to characterize the enantioselective pharmacokinetics of PNU-83894, a potential anticonvulsant candidate. The method involves solid-phase extraction (phenyl column) of the enantiomers from plasma followed by direct enantioselective separation on a beta-cyclodextrin HPLC chiral column and UV detection at 230 nm. The linear range for this method was found to be 12.5 ng/ml to 5.00 microg/ml and the intra- and inter-assay precision and accuracy for each enantiomer were <11% in all cases. The validity of this assay was also demonstrated by its application to the pharmacokinetic evaluation of PNU-83894 in the dog.     

Enantioselective LC‐ESI‐MS/MS determination of dropropizine enantiomers in rat plasma and application to a pharmacokinetic study

We developed and validated a simple, sensitive, selective and reliable LC–ESI‐MS/MS method for direct quantitation of dropropizine enantiomers namely levodropropizine (LDP) and dextrodropropizine (DDP) in rat plasma without the need for derivatization as per regulatory guidelines. Dropropizine enantiomers and carbamazepine (internal standard) were extracted from 50 μL rat plasma using ethyl acetate. LDP and DDP resolved with good baseline separation (R_s = 4.45) on a Chiralpak IG‐3 column. The mobile phase consisted of methanol with 0.05% diethylamine pumped at a flow rate of 0.5 mL/min. Detection and quantitation were done in multiple reaction monitoring mode following the transitions m/z 237 → 160 and 237 → 194 for dropropizine enantiomers and the internal standard, respectively, in the positive ionization mode. The proposed method provided accurate and reproducible results over the linearity range of 3.23–2022 ng/mL for each enantiomer. The intra‐ and inter‐day precisions were in the ranges of 3.38–13.6 and 5.11–13.8 for LDP and 4.19–11.8 and 8.89–10.1 for DDP. Both LDP and DDP were found to be stable under different stability conditions. The method was successfully used in a stereoselective pharmacokinetic study of dropropizine enantiomers in rats following oral administration of racemate dropropizine at 100 mg/kg. The pharmacokinetic results indicate that the disposition of dropropizine enantiomers is not stereoselective and chiral inversion does not occur in rats.     

Purification of Enantiomeric Mixtures in Enantioselective Synthesis: Overlooked Errors and Scientific Basis of Separation in Achiral Environment

The syntheses of optically active compounds (whether of pharmaceutical or synthetic importance, or as promising candidates as chiral ligands and auxiliaries in asymmetric syntheses) result in the formation of a mixture of products with one enantiomer predominating. Usually, the practice is to use standard open‐column chromatography for the first purification step in an enantioselective synthesis; the workup of the reaction product by crystallization or achiral chromatography would mask the real efficiency of the enantioselective methodology, since enantiomeric ratio (er) of the product may change by any of these methods. Most of the synthetic organic chemists are aware of the influence of crystallization on the er value. Majority of synthetic organic chemists are, however, not aware, while employing standard chromatography, that there may be an increase or decrease of er value. In other words, an undesired change in er goes unnoticed when such a mixture of enantiomers is isolated by chromatography on an achiral‐phase because of the prevalent concept of basic stereochemistry. Such unnoticed errors in enantioselective reactions may lead to misinterpretations of the enantioselective outcome of the synthesis. The scientific issue is, what is the difference between a racemic and nonracemic mixture in achiral environment (e.g., achiral‐phase chromatography) that leads to enantiomeric enrichment, amounting to separation of one particular enantiomer? There are sporadic reports on enantiomer separation of nonracemic mixtures in an achiral environment particularly from the scientists working in analytical chemistry. To cover/discuss all these reports is out of the scope of this article. The aim of the present report is to draw attention to the following points: i) How should the synthetic organic chemists and analytical chemists take care of the unexpected separation of enantiomers from nonracemic mixtures in a totally achiral environment? ii) What are the technical terms used in recent literature? iii) The requirement of revisiting definitions/terms (introduced in recent years, in particular) to describe such separations of enantiomers in light of prevalent scientific/chemical terminology used in the ‘language of chemistry’, the text book concept, and IUPAC background. iv) To propose logical scientific terminology or phrases for explaining the possible mechanism of separation under these conditions. v) To discuss briefly the concept/possibile phenomenon responsible for these enantioselective effects. It is also attempted to explain the effect of change of physical parameters influencing the separation from nonracemic mixture in achiral‐phase chromatography.     

Analysis of ibuprofen enantiomers in rat plasma by liquid chromatography with tandem mass spectrometry

A sensitive and selective method for the analysis of ibuprofen enantiomers by LC–MS/MS was developed and validated for the purpose of application in pharmacokinetic studies in small experimental animals. Aliquots of 200 μL plasma were submitted to liquid–liquid extraction with hexane/diisopropylether (50:50 v/v) in acid pH. Separation was accomplished in a Chirex® 3005 (250 × 4.6 mm, 5 μm) column at 25°C with a mobile phase that consisted of 0.01 M ammonium acetate in methanol at a flow rate of 1.1 mL/min. The mass spectrometer consisted of an ESI interface operating at negative ionization mode and multiple reaction monitoring. The transitions 205 > 161 and 240 > 197 were monitored for ibuprofen enantiomers and fenoprofen (internal standard), respectively. Method validation included the evaluation of the matrix effect, stability, linearity, lower LOQ, within‐run and between‐run precision, and accuracy. The lower LOQ was 25 ng/mL for each ibuprofen enantiomer, and the calibration curves showed good linearity in the range 0.025–50 μg/mL. The method was successfully applied in the investigation of pharmacokinetic disposition of ibuprofen enantiomers in rats treated orally with 25 mg/kg of the racemate. Enantioselective kinetic disposition was observed with accumulation of (+)‐(S)‐ibuprofen in rats following single oral administration.     

Determination of metrifonate enantiomers in blood and brain samples using liquid chromatography on a chiral stationary phase coupled to tandem mass spectrometry

A novel enantioselective assay is described for the simultaneous determination of the metrifonate enantiomers BAY z 7216 and BAY z 7217 in extracts of whole blood samples obtained from rats, mice, rabbits and Beagle dogs as well as in rat brain tissue using liquid chromatography tandem mass spectrometry (LC/MS/MS) with thermally and pneumatically assisted electrospray ionization (TurboIonSpray(R)). Chromatographic separation is achieved on a chiral normal phase column with a mobile phase containing 0.25% water only. The total run time per sample is 11.0 min giving chromatographic base line separation of the enantiomers. Compared with previous methods this assay offers a higher sample throughput, excellent ruggedness and higher sensitivity. The limits of quantification for each enantiomer are 5.00 microg/L from 0.5 mL whole blood and 7.50 ng/g (ppb) using 0.333 g brain tissue, respectively. Similar assay specifications have been derived for the two enantiomers. The method has been validated for the analysis of blood samples from low and high dosed preclinical pharmacokinetic and toxicokinetic studies, corresponding to two analytical working ranges like e.g. 5.00 to 1000 microg/L and 200 to 40000 microg/L (0. 200 to 40.0 mg/L). For rat brain tissue the validated concentration range is 7.50 to 750 ng/g (ppb).     

A stereospecific high-performance liquid chromatographic assay for the determination of ketoconazole enantiomers in rat plasma

A stereospecific high-performance liquid chromatographic assay was developed for the quantitation of ketoconazole enantiomers (KTZ) in rat plasma. After protein precipitation of 100 microL plasma using acetonitrile, a wash step was performed using hexane. The supernatant was removed and KTZ enantiomers and amiodarone, the internal standard, were extracted using liquid-liquid extraction with tert-butyl methyl ether. After transfer and evaporation of the organic layer, the residue was reconstituted in mobile phase and injected into the HPLC through a chiral column. The mobile phase consisted of hexane:ethanol:2-propanol with diethyl amine, pumped at 1.5 mL/min. All components eluted within 18 min. KTZ enantiomers were baseline resolved and peaks were symmetrical in appearance with no interferences. Calibration curves were linear over the range 62.5-5000 ng/mL of enantiomer. The intraday and interday CV% assessments were 相似文献   

Using dispersive liquid-liquid microextraction and liquid chromatography for determination of guaifenesin enantiomers in human urine

A simple, rapid, and efficient method, dispersive liquid–liquid microextraction (DLLME) coupled with high‐performance liquid chromatography‐fluorescence detector, has been developed for the determination of guaifenesin (GUA) enantiomers in human urine samples after an oral dose administration of its syrup formulation. Urine samples were collected during the time intervals 0–2, 2–4, and 4–6 h and concentration and ratio of two enantiomers was determined. The ratio of R‐(?) to S‐(+) enantiomer concentrations in urine showed an increase with time, with R/S ratios of 0.66 at 2 h and 2.23 at 6 h. For microextraction process, a mixture of extraction solvent (dichloromethane, 100 μL) and dispersive solvent (THF, 1 mL) was rapidly injected into 5.0 mL diluted urine sample for the formation of cloudy solution and extraction of enantiomers into the fine droplets of CH₂Cl₂. After optimization of HPLC enantioselective conditions, some important parameters, such as the kind and volume of extraction and dispersive solvents, extraction time, temperature, pH, and salt effect were optimized for dispersive liquid–liquid microextraction process. Under the optimum extraction condition, the method yields a linear calibration curve in the concentration range from 10 to 2000 ng/mL for target analytes. LOD was 3.00 ng/mL for both of the enantiomers.     

Separation of Enantiomers by On‐Line Capillary Isotachophoresis‐Capillary Zone Electrophoresis

The ability of capillary zone electrophoresis (CZE) coupled on‐line with capillary isotachophoresis (ITP) sample pretreatment in the column‐coupling capillary electrophoresis equipment to separate trace enantiomers present in samples of complex ionic matrices and enantiomers present in their mixtures at significantly differing concentrations has been studied. Enantiomers of 2,4‐dinitrophenyl labeled norleucine (DNP‐Nleu) and tryptophan enantiomers were employed as model analytes in this work while urine and mixtures of tryptophan enantiomers of differing concentrations served as model samples. Experiments performed with urine samples spiked with the DNP‐Nleu racemate at sub‐μmol/L concentrations demonstrated excellent sample pretreatment capabilities of ITP (concentration of the analytes, in‐column and post‐column sample clean up) when coupled on‐line with chiral CZE separations. In the CZE separations of enantiomers present in the samples at trace concentrations the sample pretreatment could be performed in both achiral and chiral ITP electrolyte systems. The use of a chiral electrolyte system was found to be essential in the ITP pretreatment of the samples containing the enantiomers at very differing concentrations. For example, a 2×10^–7 mol/L concentration of L‐tryptophan could be detected in the CZE separation stage of the ITP‐CZE combination in samples containing about a 10⁴ excess of D‐tryptophan only when the ITP pretreatment was carried out in the electrolyte system providing the resolution of enantiomers (α‐cyclodextrin served for this purpose in the present work). A post‐column ITP sample clean up was found effective in enhancing the destacking rate of the trace enantiomer in the CZE stage when the migration configuration of the enantiomers was less favorable (the trace constituent migrating behind the major enantiomer).     

Development and validation of a stereoselective HPLC method for the determination of the in vitro transport of nateglinide enantiomers in rat intestine

A simple stereoselective high performance liquid chromatographic method was developed for the determination of the in vitro transport of the enantiomers of nateglinide (N-(trans-4-isopropylcyclohexyl-carbonyl)-phenylalanine) in the rat intestine using a Chiralcel OJ-RH column (150 x 4.0 mm, 5 microm). The effects of the mobile phase composition, pH, the flow rate, and the temperature on the chromatographic separation were investigated. The enantioseparation was achieved at 33 degrees C using a mobile phase containing 100 mM potassium dihydrogen phosphate, pH 2.5, and ACN (32:68 v/v) delivered at a flow rate of 1 mL/min. The analytes were monitored at 210 nm and linearity (r >0.99) was obtained for a concentration range of 0.5-50 microg/mL. The LOD and LOQ were 0.2 and 0.5 microg/mL for the R-enantiomer and 0.2 and 0.8 microg/mL for the S-enantiomer, respectively. Both, the intra- and interday accuracy and precision of the calibration curves were determined. The method was successfully applied to estimate the in vitro passage of the enantiomers and the racemate of nateglinide in duodenum, jejunum, and ileum of rats. Generally, higher concentrations of nateglinide and the S-enantiomer were observed when the racemate was administered compared to administration of the individual enantiomers of nateglinide.     

Enantioselective determination of the organochlorine pesticide bromocyclen in spiked fish tissue using solid-phase microextraction coupled to gas chromatography with ECD and ICP-MS detection

A method for enantioselective determination of bromocyclen enantiomers in fish tissue has been developed. The enantiomers were resolved by capillary gas chromatography (GC) using a commercial chiral column (CP-Chirasil-Dex CB) and a temperature program from 50 degrees C (held for 1 min), raised to 140 degrees C at 40 degrees C min(-1) and then raised at 0.2 degrees C min(-1) to 155 degrees C. This enantioselective gas chromatographic separation was combined with a clean-up/enrichment procedure based on solid-phase microextraction (SPME). Under SPME optimized conditions, precision, linearity range and detection limits of the developed SPME-enantioselective GC procedure were evaluated and compared using two different detection systems: a classical electron-capture detection (ECD) and an element specific detection using inductively coupled plasma mass spectrometry (ICP-MS). The SPME-GC-ECD method exhibited an excellent sensitivity, with detection limits of 0.2 ng L(-1) for each enantiomer of bromocyclen. Although ICP-MS offered poorer detection limits (7 ng L(-1) as Br, equivalent to 36 ng L(-1) of each enantiomer) than conventional ECD detector, it proved to be clearly superior in terms of selectivity. The relative potential and performance of the two compared methods for real-life analysis has been illustrated by the determination of enantiomers of bromocyclen in spiked tissue extracts of trout.     

Development and Validation of a Chiral Liquid Chromatographic Assay for Enantiomeric Separation and Quantification of Verapamil in Rat Plasma: Stereoselective Pharmacokinetic Application

A novel, fast and sensitive enantioselective HPLC assay with a new core–shell isopropyl carbamate cyclofructan 6 (superficially porous particle, SPP) chiral column (LarihcShell-P, LSP) was developed and validated for the enantiomeric separation and quantification of verapamil (VER) in rat plasma. The polar organic mobile phase composed of acetonitrile/methanol/trifluoroacetic acid/triethylamine (98:2:0.05: 0.025, v/v/v/v) and a flow rate of 0.5 mL/min was applied. Fluorescence detection set at excitation/emission wavelengths 280/313 nm was used and the whole analysis process was within 3.5 min, which is 10-fold lower than the previous reported HPLC methods in the literature. Propranolol was selected as the internal standard. The S-(−)- and R-(+)-VER enantiomers with the IS were extracted from rat plasma by utilizing Waters Oasis HLB C18 solid phase extraction cartridges without interference from endogenous compounds. The developed assay was validated following the US-FDA guidelines over the concentration range of 1–450 ng/mL (r² ≥ 0.997) for each enantiomer (plasma) and the lower limit of quantification was 1 ng/mL for both isomers. The intra- and inter-day precisions were not more than 11.6% and the recoveries of S-(−)- and R-(+)-VER at all quality control levels ranged from 92.3% to 98.2%. The developed approach was successfully applied to the stereoselective pharmacokinetic study of VER enantiomers after oral administration of 10 mg/kg racemic VER to Wistar rats. It was found that S-(−)-VER established higher C_max and area under the concentration-time curve (AUC) values than the R-(+)-enantiomer. The newly developed approach is the first chiral HPLC for the enantiomeric separation and quantification of verapamil utilizing a core–shell isopropyl carbamate cyclofructan 6 chiral column in rat plasma within 3.5 min after solid phase extraction (SPE).     

Determination of drug enantiomers in biological samples by coupled column liquid chromatography and liquid chromatography-mass spectrometry

Liquid chromatography-mass spectrometry (LC-MS) and coupled column chromatography can be used to overcome problems likely to occur in direct separation and determination of drug enantiomers in biological samples. This is exemplified here with the direct separation and determination of terbutaline in human plasma at the nmol/l level. A beta-cyclodextrin column with an aqueous mobile phase was used for chiral separation. For coupled column chromatography, the concentration of each enantiomer was calculated from the enantiomeric area ratio and the racemate concentration. A deuterium-labelled internal standard was used in the LC-MS experiments.     

Determination of rabeprazole enantiomers in dog plasma by supercritical fluid chromatography tandem mass spectrometry and its application to a pharmacokinetic study

Rabeprazole is a novel benzimidazole proton pump inhibitor used for the treatment of gastrointestinal disorders. It is a chiral molecule that gives rise to the possibility of stereoselective pharmacokinetics. To investigate this phenomenon, a rapid and sensitive chiral assay based on supercritical fluid chromatography tandem mass spectrometry was developed and applied to the determination of (R )‐rabeprazole and (S )‐rabeprazole in dog plasma. Sample preparation involved protein precipitation with acetonitrile after the addition of (R )‐lansoprazole as internal standard. Baseline separation of enantiomers in 4.5 min was achieved on an Acquity UPC² system using an ACQUITY UPC² Trefoil CEL2 column maintained at 60°C and a mobile phase consisting of methanol/CO₂ (30:70, v/v) delivered at 2.5 mL/min. Detection was achieved by multiple reaction monitoring of the transitions at m/z 360.0→242.2 (rabeprazole) and 370.3→252.0 (internal standard) in the positive ion mode. The assay was linear in the range of 1–1000 ng/mL and free of matrix effects. Intra‐ and interday precisions were less than 10.0% with accuracy in the range of –2.6 to 3.1%. The method was successfully applied to a pharmacokinetic study of rabeprazole enantiomers after administration of a single oral dose of 10 mg racemate to beagle dogs.     

Determination of saterinone enantiomers in plasma samples with an internal standard using a Chiralcel OD column, fractionation and reversed-phase chromatography

A specific and validated high-performance liquid chromatographic method was developed for the determination of the S-(-) and R-(+) enantiomers of saterinone. 1-[(4-cyano-1,2-dihydro-6-methyl-2-oxopyridin-5-yl)phenoxyl] -3-[4-(2- methoxyphenyl)piperazin-1-yl]propan-2-ol, in plasma at the low ng/ml level. The enantiomers of saterinone and an internal standard, 1-[(4-cyano-1,2-dihydro-6-methyl-2-oxo-pyridin-5-yl)phenoxy]-3-[4-(2- ethoxyphenyl)piperazin-1-yl]propan-2-ol, were chromatographed on a chiral Chiralcel OD stationary phase. However, the S-(-) enantiomers of saterinone and the internal standard were unresolved, as were the R-(+) enantiomers of both substances. Therefore, the two fractions were collected and each was separately resolved on an achiral Polyencap A reversed-phase column and quantified. The detection limit was 0.5 ng/ml of enantiomer, allowing the determination of plasma levels up to 36 h after oral administration of 90, 150 and 180 mg of saterinone to twelve subjects.     

Enantioselective separation and dissipation of pydiflumetofen enantiomers in grape and soil by supercritical fluid chromatography–tandem mass spectrometry

Pydiflumetofen is registered in many countries and is widely used in crop production in the racemate form. However, the environmental behavior of the enantiomers has not been studied. An effective and sensitive chiral analytical method was first established for analyzing the pydiflumetofen enantiomers by supercritical fluid chromatography with tandem triple quadrupole mass spectrometry. The enantiomers could be separated and detected using the Chiralcel OD‐3 column in less than 3 min. The separation conditions were as follows: mobile phase, CO₂/methanol (80:20); flow rate, 1.0 mL/min; column temperature, 30°C, auto back‐pressure regulator pressure, 2000 psi with modified quick, easy, cheap, effective, rugged, and safe sample treatment method. The average recoveries of analytes from both matrices at three spiking levels were in the range of 84.1–103.0%. The limit of quantitation for each enantiomer was 0.005 mg/kg with a baseline resolution of approximately 1.64. The method was applied to monitor the enantioselective dissipation of pydiflumetofen in grape and soil. In grapes, (?)‐pydiflumetofen was degraded more rapidly than (+)‐pydiflumetofen. In soil, (+)‐pydiflumetofen was preferentially degraded. The data provided useful references for the risk assessment and rational use of pydiflumetofen in agriculture.     

Enantioselective determination of trantinterol in rat plasma by ultra performance liquid chromatography-electrospray ionization mass spectrometry after derivatization

An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the determination of trantinterol enantiomers in rat plasma. Diphenhydramine was employed as the internal standard. The plasma samples were prepared using liquid-liquid extraction with n-hexane-dichloromethane-isopropanol (20:10:1, v/v/v) as the extractant. Trantinterol enantiomers after pre-column derivatization using diacetyl-l-tartaric anhydride (DATAAN) were separated on a C18 column using a gradient solvent programme. The mobile phase was composed of 3 mM ammonium acetate and acetonitrile. The detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI). Linear calibration curve for each enantiomer was obtained in the concentration range of 1-80 ng/mL, with limit of quantification (LOQ) of 1 ng/mL. The intra- and inter- precision (R.S.D.) values were below 9.6% and accuracy (R.E.) was from −2.4 to 6.2% at all quality control (QC) levels. The developed method was applied to the enantioselective pharmacokinetic study of trantinterol in rats.     

Analytical and semipreparative resolution of ranolazine enantiomers by liquid chromatography using polysaccharide chiral stationary phases

Novel HPLC methods were developed for the analytical and semipreparative resolution of new antianginal drug ranolazine enantiomers. Good baseline enantioseparation was achieved using cellulose tris (3,5-dimethylphenylcarbamate) (CDMPC) chiral stationary phases (CSPs) under both normal-phase and polar organic modes. The validation of the analytical methods including linearity, LODs, recovery, and precision, and the semipreparative resolution of ranolazine racemate were carried out using methanol as mobile phase without any basic and acidic additives under polar organic mode, using CDMPC CSPs. At analytical scale, the elution times of both enantiomers were less than 7.5 min at 20 degrees C and 1.0 mL/min, with the separation factor (a) 1.88 and the resolution factor (R(s)) 2.95. At semipreparative scale, about 14.3 mg/h enantiomers could be isolated and elution times of both enantiomers were less than 13 min at 2.0 mL/min. To increase the throughput, the technique of overlapping injections was used. The first eluted enantiomer was isolated with a purity of 99.6% enantiomer excess (e.e.) and > 99.0% yield. The second enantiomer was isolated with a purity of 98.8% e.e. and > 99.0% yield. In addition, optical rotation and circular dichroism spectroscopy of both ranolazine enantiomers isolated were also investigated.