Chiralpak IA Column Research Articles

Enantiomeric Separation of (R)-5-(1-Hydroxyethyl)-2-(pyridine- 2-yl)-[1, 3, 4]-thiadiazole, an Intermediate of Nafithromycin on Immobilized Amylose Based Stationary Phase

Chiral high performance liquid chromatography method for the separation of (R)-5-(1- Hydroxyethyl)-2-(pyridine-2-yl)-[1, 3, 4]-thiadiazole (R-alcohol) an intermediate of new antibiotic Nafithromycin (NFT) has been developed and validated. NFT is a ketolide class of antibiotic currently under Phase III clinical trials in India to treat community acquired bacterial pneumonia. Chiral separation of the enantiomers with resolution >2 was accomplished on Chiralpak IA column using a mixture of n-hexane and isopropanol (IPA) in the ratio of (90:10; v/v) as an elution solvent, run at a flow rate of 1.2 mL.min-1. The column was maintained at 25°C. The analytes were detected at 254 nm. The developed method was extensively validated as per the international council for harmonisation of technical requirements for pharmaceuticals for human use guideline. Sensitivity of the method was adequate to control the passage of unwanted enantiomer to next step with limit of quantification (LOQ) of the undesired enantiomer (S)-5-(1-Hydroxyethyl)-2-(pyridine- 2-yl)-[1, 3, 4]-thiadiazole (S-alcohol) of 0.37 µgmL-1. Mean recovery of the S-alcohol was 98.9±8.7%. During development influence of column oven temperature on the chiral separation was assessed.

Enantiomeric Separation and Thermodynamic Investigation of (R)-N-Tert-Butoxy Carbonyl-Piperidine-3-Carboxylic Acid Hydrazide, a Key Starting Material of Zidebactam.

A new selective, accurate and precise chiral high-performance liquid chromatography method for the separation of (R)-N-tert-butoxy carbonyl-piperidine-3-carboxylic acid hydrazide (RE) and its enantiomer was developed. RE is a key starting material of novel β-lactam enhancer drug Zidebactam. Chiral resolution of more than 10 was achieved on Chiralpak IA column using mobile phase consisting of n-hexane, ethanol in the ratio of 70:30, v/v. The flow rate of the mobile phase was 1.0mLmin-1 and the column oven temperature was 30°C. Detection was carried out at 225nm. The developed method was validated as per the International Conference on Harmonization guideline. Limit of detection and limit of quantification of the enantiomeric impurity (S)-N-tert-butoxy carbonyl-piperidine-3-carboxylic acid hydrazide (SE) was 2.5 and 7.5μgmL-1, respectively. Mean recovery of the SE was 96.83±1.4%. The effect of thermodynamic parameters on the chiral separation was evaluated.

Enantioselective LC-MS/MS method for the determination of cloperastine enantiomers in rat plasma and its pharmacokinetic application.

Cloperastine is a central antitussive used to reduce the frequency and intensity of coughing on a short-term basis. In this study, a reliable chiral LC-MS/MS technology has been developed for the quantification of cloperastine enantiomers in the rat plasma. Carbinoxamine was selected as the internal standard. The enantioseparation of cloperastine was performed on a Chiralpak IA column with a mobile phase composed of acetonitrile-water-ammonium hydroxide (80:20:0.1, v/v/v) at a flow rate of 0.6 mL/min. Cloperastine enantiomers were detected by mass spectrometry in multiple reaction monitoring mode with a positive electrospray ionization source. The method was validated over the linear concentration range of 0.05 to 10.0 ng/mL (5.0 × 10-4 ng to 0.10 ng) for both enantiomers. The lower limit of quantification (LLOQ) for each analyte was determined as 0.05 ng/mL. The relative standard deviations (RSDs) of intraday and interday precision was less than 13.9%, and the relative error (RE) of accuracy ranged from -5.4% to 6.1%, which were within the acceptance criteria. Finally, an application to the stereoselective pharmacokinetics of cloperastine in rats was successfully realized in our assay. The developed method on a commercially available Chiralpak IA column under isocratic mobile phase is advantageous to analyze cloperastine enantiomers in plasma samples collected for enantioselective metabolism or drug interaction studies.

Rapid and efficient chiral method development for lamivudine and tenofovir disoproxil fumarate fixed dose combination using ultra-high performance supercritical fluid chromatography: A design of experiment approach

Fixed dose combination (FDC) of tenofovir disoproxil fumarate (TDF) and lamivudine (3TC) is one of the most preferred FDC for the treatment of acquired immunodeficiency syndrome (AIDS)/human immunodeficiency virus (HIV) infection. To the best of authors’ knowledge there are no reported methods for chiral purity estimation of both drugs simultaneously from a FDC. The current study was focused on the development of a single chiral method uisng supercritical fluid chromatography (SFC) for separation of stereoisomers of TDF and 3TC combination employing design of experiment (DoE) approach. Method development was planned in three steps by using different experimental designs for each step. I-optimal, Taguchi orthogonal array and face-centred central composite designs (CCD) were employed for primary parameter selection, secondary parameter screening and final method optimization, respectively. All six stereoisomers were separated in a 10 minute run on Chiralpak IA column with carbon di-oxide /methanol (containing 0.5 % v/v n-butylamine) as mobile phase at 1.5 mL/min in gradient mode. The optimized method was verified for performance through establishing specificity, precision, linearity, accuracy, limit of quantification, and solution stability. Resolution between each isomeric pair was more than 1.5. The method was found to be linear from 1.5 µg/mL to 7.5 µg/mL for 3TC and 7.5 µg/mL to 37.5 µg/mL for TDF stereoisomers. The R2 values for all the linearity curves for undesired isomers were greater than 0.995. The method proved to be rapid, reproducible and efficient to quantify stereoisomers of both drugs in a single run.

Separation and quantitation of notopterol enantiomers in notopterygii rhizoma et radix using solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry

In this study, a specific, sensitive, and reliable high performance liquid chromatography-tandem mass spectrometry method has been developed and validated for the quantitative determination of notopterol enantiomers in Notopterygii Rhizoma et Radix. Solid-phase extraction was used for the extraction of notopterol enantiomers from Notopterygii Rhizoma et Radix. Enantiomeric separation of notopterol was achieved on a Chiralpak IA column with the mobile phase consisting of acetonitrile-water (50:50, v/v) at a flow rate of 0.6 mL/min. Quantification was performed on a triple quadrupole tandem mass spectrometry equipped with an electrospray ionization source in the positive ionization and multiple reaction monitoring mode. The lower limit of quantification and lower limit of detection were 0.09 and 0.04 mg/g for each enantiomer in NRR samples. And each enantiomer showed good linearity (R2≥0.999) in the range of 0.09–9.55 mg/g. The precision, repeatability, and stability were all within satisfaction. The average recoveries of (-)-notopterol and (+)-notopterol were demonstrated to be 99.3 % and 101.1 %, respectively, with the relative standard deviations less than 5.0 %. Finally, the validated method was successfully applied to the quantification of notopterol enantiomers in Notopterygii Rhizoma et Radix from different sources.

Development and Validation of an New High Performance Liquid Chromatography Method for Determination of Apixaban Isomers

The purpose of this research study is to develop a novel, simple, precise, accurate and economical method for determination of Apixaban API isomers. Apixaban API has three isomer as ortho, meta and para. In reverse phase and normal phase chromatography it was very difficult to separate these isomer; hence new chiral technique was adopted. This chromatographic method was developed on chiralpak IA column (250×4.6×5µm) with isocritic technique. The detection of isomeric impurities were observed at wavelength 290nm. This analytical method was validated as per ICH guideline and regression analysis showed R value (correlation coefficient) > 0.999 for Apixaban API and its isomeric impurities. A solution of Apixaban in dichloromethane was found stable up to 48 hrs. The degradation study was done within the given guidelines prescribed by ICH. The method is validated for Linearity, Accuracy and Precision.

Enantiomeric Separation and Thermodynamic investigation of (R)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)- [1,3,4]-thiadiazole, a Key Intermediate of Nafithromycin

A selective and precise chiral high performance liquid chromatography method for the separation of (R)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)-[1, 3, 4]-thiadiazole (RE) has been developed and validated. It is an intermediate of a novel antibiotic nafithromycin. Nafithromycin is a ketolide class antibiotic being developed to treat community acquired bacterial pneumonia. Enantiomeric separation was achieved on Chiralpak IA column using mobile phase consisting of n-hexane and ethanol in the ratio of (15:85; v/v) with the resolution of more than 3. Separation was achieved at flow rate of 1.0 mL min−1 and column temperature 30°C. The eluent was monitored at 254 nm. The developed method was validated as per the guideline. The method was found to be selective, precise, accurate and linear. Limit of detection and limit of quantification of the undesired enantiomer (S)-5-[1-(4-Nitrobenzylsulfonyloxy)-ethyl]-5-(pyridine-2-yl)- [1, 3, 4]-thiadiazole (SE) was 0.11 and 0.35 μgmL−1 respectively. Recovery of the SE was found to be in the range of 104.52 % and 105.83 %. The impact of thermodynamic parameters on the chiral separation was evaluated.

ENANTIOMETRIC SEPARATION OF SITAGLIPTIN IN A FIXED DOSE COMBINATION FORMULA OF SITAGLIPTIN AND METFORMIN BY A CHIRAL LIQUID CHROMATOGRAPHIC METHOD

Objective: Sitagliptin phosphate and metformin hydrochloride tablet is an FDA approved combination product for the treatment of diabetes mellitus type 2. There are no reported evidence for estimation of undesired (S)-sitagliptin in a combination product. The objective of this study was to develop a high sensitive liquid chromatography method for the determination of (S)-enantiomer of sitagliptin phosphate in a fixed dose combination formula of metformin and sitagliptin.
 Methods: The proposed novel high-performance liquid chromatography (HPLC) method uses programmed gradient elution of a mixture of ethanol-diethylamine(DEA) 100:0.1 (v/v) as mobile phase-A and a mixture of methanol-water 60:40 (v/v) as mobile phase-B. The chromatographic conditions were designed to nullify the metformin interference and in which sitagliptin enantiomers elute first and followed by metformin. A satisfactory resolution (≥2.5) between (S)-sitagliptin and active form (R)-sitagliptin was achieved with gradient elution on Chiralpak IA column (5μm, 4 × 250 mm) at a flow rate of 0.5 ml/min and the detector wavelength set at 265 nm. The injection volume set as 10 µl. The developed method has been validated as per the International Conference on Harmonisation (ICH) guidelines.
 Results: The proposed HPLC method for determination of (S)-sitagliptin, showed good linearity in the concentration range of 0.5 µg/ml to 13.6 µg/ml and capable to quantify accurately up to the lowest level (LOQ) of 0.017%. The validated method was successfully applied to quantify the (S)-sitagliptin for different marketed formulations of sitagliptin with metformin and sitagliptin alone, and the corresponding recovery values were found to be in the range of 95.1% to 98.4%.
 Conclusion: The proposed validated HPLC method was found to be suitable for the quantitative determination of (S)-sitagliptin in the formulations of sitagliptin with metformin and sitagliptin alone.

Validated LC Method for Determination of Enantiomeric Purity of Apremilast Using Polysaccharide-Type Stationary Phases in Polar Organic Mode

Enantioseparation of an anti-psoriatic agent, apremilast (APR), was performed by HPLC using polysaccharide-type chiral stationary phases in polar organic mode for the first time. The separation capability of six different chiral columns (Chiralpak AD, Chiralpak IA, Chiralpak AS, Lux Amylose-2, Chiralcel OD and Chiralcel OJ-H) was investigated using neat MeOH and ACN. During the preliminary experiments the best results were obtained on Chiralpak IA column with ACN (Rs = 5.4). The effects of binary mobile phases on the resolutions and retention factors were also investigated containing different percentages of MeOH:ACN. U-shaped retention pattern was obtained when plotting the retention factors of the APR enantiomers versus the MeOH content of the binary mobile phases on Chiralpak IA column. For further method optimizations an L25 orthogonal array table was employed altering the concentration of MeOH in ACN, column temperature, and flow rate. The best result was achieved on Chiralpak IA column with 80/20 (v/v%) MeOH/ACN with 0.7 mL min−1 flow rate at 25 °C (Rs = 5.4, t2 = 7.45 min). Thermodynamic analysis revealed an enthalpy-driven enantioseparation. The developed HPLC method was validated according to the ICH guideline Q2(R1) and proved to be reliable, linear, precise and accurate for the determination of 0.1% R-enantiomer as chiral impurity in S-APR as well as quantification of the S-enantiomer.

Validated Chiral LC-ESI-MS/MS Method for the Simultaneous Quantification of Darolutamide Diastereomers and Its Active Metabolite in Mice Plasma: Application to a Pharmacokinetic Study.

A simple, selective and reliable LC-MS/MS method was developed and validated for the simultaneous quantitation of darolutamide diastereomers (diastereomer-1 and diastereomer-2) and its active metabolite i. e. ORM-15341 in mice plasma using warfarin as an internal standard (IS) as per the regulatory guidelines. Plasma samples were extracted by liquid-liquid extraction and the chromatographic separation was achieved on a Chiralpak IA column with an isocratic mobile phase 5 mM ammonium acetate:absolute alcohol (20:80, v/v) at a flow rate of 1.0 mL/min. Detection and quantitation was done by multiple reaction monitoring on a triple quadrupole mass spectrometer following the transitions: m/z 397→202, 395→202 and 307→250 for darolutamide diastereomers, ORM-15341 and the IS, respectively in the negative ionization mode. The calibration curves were linear (r>0.992) in the range of 100-2400 ng/mL for all the analytes. The intra- and inter-day precisions were in the range of 1.25-10.2 and 1.58-12.3; 2.85-5.68 and 1.85-9.58; 2.34-12.1 and 2.58-7.38 for diastereomer-1, diastereomer-2 and ORM-15341, respectively. Both diastereomers and ORM-15341 were found to be stable under different stability conditions. The validated method was applied to a pharmacokinetic study in mice.

Validation of a chiral LC-MS/MS-ESI method for the simultaneous quantification of darolutamide diastereomers in mouse plasma and its application to a stereoselective pharmacokinetic study in mice.

A simple, selective and reliable LC-MS/MS method was validated for simultaneous quantitation of darolutamide diastereomers in 50 μL mouse plasma using warfarin as an internal standard (IS) as per regulatory guidelines. Plasma samples were extracted by liquid-liquid extraction and the chromatographic separation was achieved on a Chiralpak IA column with an isocratic mobile phase 5 mm ammonium acetate-absolute alcohol (20:80, v/v) at a flow rate of 1.0 mL/min. Detection and quantitation was done in multiple reaction monitoring mode following the transitions m/z 397 → 202 and 307 → 250 for darolutamide diastereomers and the IS, respectively, in the negative ionization mode. The linearity range was 100-2400 ng/mL for each diastereomer. The intra- and inter-day precisions were in the ranges of 1.78-4.20 and 4.34-14.6, and 3.63-4.74 and 4.78-5.15 for diastereomer-1 and diastereomer-2, respectively. Both diastereomers were found to be stable under different stability conditions. The validated method was applied to a pharmacokinetic study in mice. Following oral administration of darolutamide at 10 mg/kg, maximum concentration in plasma was 4189 and 726 ng/mL for diastereomer-1 and diastereomer-2, respectively. The terminal half-life was found to be ~0.50 h for both the diastereomers. The AUC(0-t) was found to be 18,961 ng*h/mL for diastereomer-1 and 1340 ng*h/mL diastereomer-2.

Liquid chromatographic separation and thermodynamic investigation of lorcaserin hydrochloride enantiomers on immobilized amylose-based chiral stationary phase.

A novel liquid chromatographic method was developed for enantiomeric separation of lorcaserin hydrochloride on Chiralpak IA column containing chiral stationary phase immobilized with amylose tris (3.5-dimethylphenylcarbamate) as chiral selector. Baseline separation with resolution greater than 4 was achieved using mobile phase containing mixture of n-hexane/ethanol/methanol/diethylamine (95:2.5:2.5:0.1, v/v/v/v) at a flow rate of 1.2mL/min. The limit of detection and limit of quantification of the S-enantiomer were found to be 0.45 and 1.5μg/mL, respectively; the developed method was validated as per ICH guideline. The influence of column oven temperatures studied in the range of 20°C to 50°C on separation was studied; from this, retention, separation, and resolution were investigated. The thermodynamic parameters ΔH°, ΔS°, and ΔG° were evaluated from van't Hoff plots,(Ink' versus 1/T) and used to explain the strength of interaction between enantiomers and immobilized amylose-based chiral stationary phase.

Validation of an enantioselective LC-MS/MS method to quantify enantiomers of (±)-OTX015 in mice plasma: Lack of in vivo inversion of (-)-OTX015 to its antipode.

A highly sensitive, specific and enantioselective assay has been validated for the quantitation of OTX015 enantiomers [(+)-OTX015 and (-)-OTX015] in mice plasma on LC-MS/MS-electrospray ionization as per regulatory guidelines. Protein precipitation was used to extract (±)-OTX015 enantiomers and internal standard (IS) from mice plasma. The active [(-)-OTX015] and inactive [(+)-OTX015] enantiomers were resolved on a Chiralpak-IA column using an isocratic mobile phase (0.2% ammonia/acetonitrile 20 : 80, v/v) at a flow rate of 1.2 mL/min. The total run time was 6.0 min. (+)-OTX015, (-)-OTX015 and IS eluted at 3.34, 4.08 and 4.77 min, respectively. The MS/MS ion transitions monitored were m/z 492 → 383 for OTX015 and m/z 457 → 401 for IS. The standard curves for OTX015 enantiomers were linear (r2 >0.998) in the concentration range 1.03-1030 ng/mL. The inter- and intraday precisions were in the range 2.20-13.3 and 8.03-12.1% and 3.80-14.4 and 8.97-13.6% for (+)-OTX015 and (-)-OTX015, respectively. Both the enantiomers were found to be stable in a battery of stability studies. This novel method has been applied to the study of stereoselective oral pharmacokinetics of (-)-OTX015 and unequivocally demonstrated that (-)-OTX015 does not undergo chiral inversion to its antipode in vivo in mice.

Development and Validation of a Chiral Liquid Chromatographic Method for Quantitative Determination of (+)-OTX015 in (−)-OTX015

A simple, rapid and robust enantioselective method was developed and validated for the quantitation of OTX015 enantiomers [(−)-OTX015 and (+)-OTX015] with ultrahigh-performance liquid chromatography (UHPLC) as per ICH guidelines. The active [(−)-OTX015] and inactive [(+)-OTX015] enantiomers were resolved on a Chiralpak-IA column using methanol consisting of 0.1 % diethyl amine at a flow rate of 1.0 mL min−1. The resolution between the enantiomers was found to be more than 3.7 in the optimized method. The developed method was extensively validated and proven to be robust. The calibration curve for (+)-OTX015 showed excellent linearity over the concentration range of 10–100 µg mL−1. The limit of detection and the limit on quantitation for (+)-OTX015 were 5 and 10 µg mL−1, respectively. The recovery for (+)-OTX015 ranged between 100.7 and 102.5 % in the bulk drug sample of (−)-OTX015. The proposed method was found to be suitable and accurate for quantitative determination of (+)-OTX015 in bulk drug.

Enantiomeric resolution and simulation studies of four enantiomers of 5-bromo-3-ethyl-3-(4-nitrophenyl)-piperidine-2,6-dione on a Chiralpak IA column

Enantiomeric resolution and simulation studies of four enantiomers of 5-bromo-3-ethyl-3-(4-nitrophenyl)-piperidine-2,6-dione on a Chiralpak IA column were presented.

Dried blood spot analysis of (+) and (-) darunavir enantiomers on immobilized amylose tris-(3, 5-dimethylphenylcarbamate) LC and its application to pharmacokinetics.

Dried blood spot analysis is an innovative novel blood sampling technique gaining interest in drug discovery and development processes owing to its inherent advantages over the conventional whole blood, plasma or serum sample collection. The present manuscript describes the development and validation of a highly sensitive and precise method of evaluation of pharmacokinetics of (+) and (-) darunavir enantiomers on rat dried blood spots. The enantiomers on rat dried blood spots were extracted into methanol and separated by LC on a Chiralpak IA column using hexane and ethanol containing 0.1% DEA (75:25, v/v) as a mobile phase at 20°C; both the enantiomers were detected at 266 nm using a photodiode array detector. The method was validated in terms of selectivity, linearity, accuracy, precision and stability as per the US Food and Drug and Administration guidelines. The hematocrit effect on extraction recovery was evaluated and the mean recoveries of (-) and (+) enantiomers of darunavir from dried blood spots were found to be 85.76 and 88.91% respectively. The intra- and inter-day precision and accuracy were 3.1-8.4 and 0.8-4.8% respectively. The developed method was successfully applied to a pharmacokinetic study of (+) and (-) enantiomers of darunavir on rat dried blood spots.

Enantiomeric separation of indoxacarb on an amylose‐based chiral stationary phase and its application in study of indoxacarb degradation in water

Direct semipreparative enantioseparation of indoxacarb was performed on a semipreparative Chiralpak IA column using normal-phase high-performance liquid chromatography (HPLC) with n-hexane-isopropanol-ethyl acetate (70:20:10) mixture as mobile phase. Degradation of indoxacarb (2.33S + 1R) and its two enantiopure isoforms in three aqueous buffer solutions and four water samples collected from natural water sources was then elucidated by HPLC analysis on Chiralpak IA column. Degradation of all three indoxacarbs complied with first-order kinetics and demonstrated linearity with regression coefficients R(2) > n0.88. Indoxacarb (2.33S + 1R) underwent enantioselective degradation in river water, rain water, and buffer solution of pH 7.0. Enantiopure S-(+)-indoxacarb and R-(-)-indoxacarb were both found to be configurationally stable in water.

Simultaneous stereoselective analysis of naftopidil and O‐desmethyl naftopidil enantiomers in rat feces using an online column‐switching high‐performance liquid chromatography method

A novel online column-switching chiral high-performance liquid chromatography method was developed and validated for the simultaneous determination of naftopidil (NAF) and its O-desmethyl metabolites (DMN) enantiomers in rat feces. Direct and multiple injections of supernatant from rat feces homogenate were allowed through the column-switching system. Analyte extraction was performed on the Capcell Pak mixed-functional column by acetonitrile-phosphate buffer (pH 7.4; 10 mm; 8:92, v/v) flowing at 1 mL/min. Separation of NAF and DMN enantiomers was achieved on the Chiralpak IA column by methanol-acetonitrile-acetate buffer (pH 5.3; 5 mm; 45:33:22, v/v/v) flowing at 0.5 mL/min. The analytes were measured with a fluorescence detector at 290 nm (λ(ex)) and 340 nm (λ(em)). The validated method showed a good linearity [22.5-15,000 ng/mL for (+)-/(-)-NAF; 35-25,000 ng/mL for (+)-/(-)-DMN] and the lowest limits of quantification for NAF and DMN enantiomers were 22.5 and 35 ng/mL, respectively. Both intra- and inter-day variations were <10%. The assay was successfully applied to the fecal excretion of NAF and DMN enantiomers in rat after single oral administration of (±)-NAF. Nonstereoselective excretion of (+)- and (-)-NAF was found in feces, while stereoselective excretion of (+)- and (-)-DMN was observed with higher excretion levels of (+)-DMN, indicating that there may exist stereoselective metabolism for NAF enantiomers.

COMPARATIVE STUDIES OF ENANTIOSEPARATION OF SOME AMINO ACIDS AND N-PROTECTED AMINO ACIDS IN NORMAL PHASE HPLC AND ANALYSIS OF UNUSUAL PEAK SHAPE

Comparative studies of enantioseparation of some amino acids and N-protected amino acids were performed using a Chiralpak IA column in normal phases HPLC. Better resolution results were obtained for N-protected amino acids compared with the studied amino acids at the same conditions. The effects of type and concentration of alcohol modifier in mobile phase, concentration of acidic additive trifluoroacetic acid, and column temperature on enantioseparation were also investigated. The experimental results showed that the separation factor and resolution factor were both high when ethanol was used as alcohol modifier in mobile phase. When the mobile phase contained 35% (v/v) ethanol, the separation factor of all the enantiomers was the highest. A trace amount of trifluoroacetic acid promotes enantioseparation regardless of the nature of the chiral solutes. The retention time of investigated enantiomers decreased with the increase of column temperature. The chromatographic peak shape of enantiomers separation was almost symmetrical except for the resolution of phenylalanine and 3-(3,4-dihydroxyphenyl)alanine, in which chromatographic peak of the first eluted enantiomer was unusual lower and wider than that of the second eluted enantiomer. The mechanism of the unusual peak shape from enantioseparation of phenylalanine and 3-(3,4-dihydroxyphenyl)alanine was analyzed.

Determination of naftopidil enantiomers in rat plasma using chiral solid phases and pre-column derivatization high-performance liquid chromatography

Two bioanalytical HPLC methods (chiral solid phases (CSPs) HPLC and pre-column derivatization HPLC) were developed and validated for the determination of naftopidil enantiomers in rat plasma. Analytes were extracted from biomaterials by liquid–liquid extraction. The pre-column derivatization HPLC method employed (+)-diacetyl-l-tartaric anhydride (DATAN) as the pre-column derivatization reagent, and subsequent separation of diastereomers was conducted on an Agilent Hypersil ODS column with a mixture of methanol–acetonitrile–phosphate buffer (pH 4.1; 20mM) (40:30:30, v/v/v) flowing at 1mL/min as the mobile phase. The CSPs HPLC method utilized a Chiralpak IA column with a mobile phase of methanol–acetonitrile–acetate buffer (pH 5.3; 5mM) (50:25:25, v/v/v) flowing at 0.5mL/min. In both methods, the analytes were monitored using a fluorescence detector with an excitation wavelength of 290nm and an emission wavelength of 340nm. Both methods were consistent (RSD<15% by the derivatization method and<10% by the CSPs method) and linear (r>9950). Compared to the pre-column derivatization method, the CSPs method had lower quantification limits (10.6/9.6ng/mL of (+)-/(−)-naftopidil by derivatization method and 1.1/1.8ng/mL of (+)-/(−)-naftopidil by CSPs method), and was simpler to carry out. The validated CSPs method was successfully applied in a pharmacokinetic study of naftopidil enantiomers in rats, which showed that pharmacokinetic parameters of (+)- and (−)-NAF after intravenous administration of (±)-NAF were similar.