Metoprolol Enantiomers Research Articles

Enantiocomplementary synthesis of β-adrenergic blocker precursors via biocatalytic nitration of phenyl glycidyl ethers

Enantiopure β-nitroalcohols, as an important class of nitro-containing compounds, are essential building blocks in pharmaceutical and organic chemistry, particularly for the synthesis of β-adrenergic blockers. In this study, we present the successful protein engineering of halohydrin dehalogenase HHDHamb for the enantioselective bio-nitration of various phenyl glycidyl ethers to the corresponding chiral β-nitroalcohols, using the inexpensive, commercially available, and safer nitrite as a nitrating agent. The chiral (R)- and (S)-1-nitro-3-phenoxypropan-2-ols were synthesized by the several enantiocomplementary HHDHamb variants through the whole-cell biotransformation, which showed good catalytic efficiency (up to 43% isolated yields) and high optical purity (up to >99% ee). In addition, we also demonstrated that the bio-nitration method was able to tolerate the substrate at a high concentration of 1000 mM (150 g/L). Furthermore, representative synthesis of two optically active enantiomers of the β-adrenergic blocker metoprolol was successfully achieved by utilizing the corresponding chiral β-nitroalcohols as precursors.

Physiologically Based Pharmacokinetic Modeling of Metoprolol Enantiomers and α-Hydroxymetoprolol to Describe CYP2D6 Drug-Gene Interactions.

The beta-blocker metoprolol (the sixth most commonly prescribed drug in the USA in 2017) is subject to considerable drug–gene interaction (DGI) effects caused by genetic variations of the CYP2D6 gene. CYP2D6 poor metabolizers (5.7% of US population) show approximately five-fold higher metoprolol exposure compared to CYP2D6 normal metabolizers. This study aimed to develop a whole-body physiologically based pharmacokinetic (PBPK) model to predict CYP2D6 DGIs with metoprolol. The metoprolol (R)- and (S)-enantiomers as well as the active metabolite α-hydroxymetoprolol were implemented as model compounds, employing data of 48 different clinical studies (dosing range 5–200 mg). To mechanistically describe the effect of CYP2D6 polymorphisms, two separate metabolic CYP2D6 pathways (α-hydroxylation and O-demethylation) were incorporated for both metoprolol enantiomers. The good model performance is demonstrated in predicted plasma concentration–time profiles compared to observed data, goodness-of-fit plots, and low geometric mean fold errors of the predicted AUClast (1.27) and Cmax values (1.23) over all studies. For DGI predictions, 18 out of 18 DGI AUClast ratios and 18 out of 18 DGI Cmax ratios were within two-fold of the observed ratios. The newly developed and carefully validated model was applied to calculate dose recommendations for CYP2D6 polymorphic patients and will be freely available in the Open Systems Pharmacology repository.

Chiral nanocomposite of sulfobutyl ether-β-cyclodextrin embedded in carbon nanofibers for enantioselective electrochemical discrimination of amlodipine, metoprolol and clenbuterol enantiomers

A highly sensitive and selective electrochemical chiral sensor was developed based on the competitive supramolecular interaction of carbon nanofibers (CNFs) embedded sulfobutyl ether-β-cyclodextrin (SBE-β-CD) with optically active cationic drugs at glassy carbon electrode (GCE). The difference in intermolecular hydrogen bonding/stability constant/enantioselectivity coefficient and Gibbs free energy of anionic host SBE-β-CD with enantiomers of amlodipine (R-/S-AML), clenbuterol (R-/S-CBL) and metoprolol (R-/S-MET) as a guest paved the way for efficient discrimination. The proposed sensing platform (CNFs-SBE-β-CD/GCE) could recognize the aforementioned enantiomers based on the discernible difference of peak potential (S/R-AML (ΔEp = 135 mV), R/S-MET (ΔEp = 99 mV) and R/S-CBL (ΔEp = 111 mV). The binding mechanisms and thermodynamic study of the enantiospecific behavior have been investigated using the host-guest chemistry approach inside the nanocavity and results suggest that S-AML, R-MET, and R-CBL show stronger stability constants than their antipodes. Formation of the diastereomeric complex was taken as a measure of enantioselectivity and experimental results indicated that anionic SBE-β-CD is a better chiral ligand than neutral cyclodextrins. The fabricated sensor could be a useful low-cost electrochemical tool for molecular recognition of a variety of cationic species not only of drugs but also from other sources.

Analysis of metoprolol enantiomers via reverse phase (RP-HPLC) with M-ß-Cyclodextrin as mobile additive

Enantiomeric separation of the racemic metoprolol was investigated using a reverse phase HPLC (RP-HPLC) with Methyl-beta-cyclodextrin (M-B-CD) as chiral mobile phase additive. A comparison of the enantioseparation of the racemic metoprolol, the system suitability, linearity, accuracy, limit of detection and quantification was undertaken to show the performance between two C18 columns, a Zorbax Eclipse XDB C-18 column (15 cm x 10 mm, 10 μm) and a Syncronis C18 HPLC column (250 mm x 4.6 mm, 5.0 μm) using high performance liquid chromatography with the same condition of mobile phase composition, pH value of the mobile phase and concentration of chiral additives. The resolution was achieved using a mobile phase consisting of a mixture of aqueous solution (3.5 g M-ß-CD in 300 ml H20), methanol with a volumetric ratio of 86:14 (v/v) and a flow rate of 1.0 ml/min and 0.5 ml/min for the columns respectively. Conversion of S-metoprolol found in this study are 60%, 51%, 15%.

Development of a UPLC method with Chiral Derivatization for the Determination of Atenolol and Metoprolol Enantiomers in Tablet Preparations

Development of a UPLC method with Chiral Derivatization for the Determination of Atenolol and Metoprolol Enantiomers in Tablet Preparations

Modeling multiple chemical equilibrium in chiral extraction of metoprolol enantiomers from single-stage extraction to fractional extraction

Enantioselective extraction of metoprolol (MT) enantiomers with di-cyclohexyl (D)-tartrate (DT) and boric acid (BA) as chiral extractant was performed. The process involving multiple chemical equilibrium is very complicated and the process optimization is difficult. On the basis of an interfacial reaction mechanism, a single-stage extraction model was established. The operation conditions of pH and DT to BA ratio were obtained through simulation and optimization of the equilibrium of the two phase extraction system. Based on the single-stage extraction model and the law of mass conservation, a fractional extraction model was established to simulate and optimize the fractional extraction process. To pursue a high productivity and reduce the required stages, a high feed to aqueous phase ratio (F/W = 1) and an asymmetric separation mode were applied. By asymmetric separation where the optical purity of the product in extract phase and raffiniate phase is not equal, enantiomeric excess (ee) value for the eutomer of MT can reach up to 98.64% and yield can reach up to 64.68% with 20 extraction stages.

Kinetic study on reactive extraction of metoprolol enantiomers with cyclohexyl (D)-tartrate and boric acid as combined chiral selector

Abstract This paper reports on the kinetic study on reactive extraction of metoprolol (MT) enantiomers using cyclohexyl (D)-tartrate (DT) and boric acid (BA) as combined chiral selector in a modified Lewis cell. An interfacial reaction model is applied to understanding the experimental data. The MT enantiomers are extracted enantioselectively from aqueous phase through the interfacial reaction among BA, DT and MT. Important factors that influence the kinetics of extraction are investigated. The optimal conditions for kinetic study were as follows: agitation speed of 75 rpm, interfacial area of 12.56 cm2, pH of 6, initial DT concentration of 0.075 mol/L, initial BA concentration of 0.1 mol/L, and initial MT concentration of 5 mmol/L at temperature of 5 °C. Important parameters concerning extraction kinetics are evaluated through multiple linear regression analysis of the experimental data. The interfacial reaction is 0.4, 0.6 and 1 order separately with respect to BA, MT and DT, and the total order of reaction is about 2. The forward rate constants have been found to be 5.24 × 10−4 L/(mol s) for (R)-MT and 2.73 × 10−4 L/(mol s) for (S)-MT.

Application of rifampicin as a chiral selector for enantioresolution of basic drugs using capillary electrophoresis

Rifampicin, a member of rifamycin sub-class of antibiotics which belongs to the naphthalenic ansamycin class of antibiotics, has a characteristic ansa structure, i.e., a ring structure or chromophore spanned by an aliphatic chain. The present work was designed to evaluate its potential as a chiral selector (CS) as its structure consisting of nine stereogenic centers, an aromatic moiety and several functional groups (i.e., one imine, one amide, one acetoxy residue, two aliphatic hydroxyl and three phenolic hydroxyl groups) was expected to instigate multiple enantioselective interactions, namely, hydrogen bonding and inclusion complexation with chiral analytes, and therefore resulting in efficient enantioseparations. Systematic experiments were performed to investigate the effects of concentration of CS, composition of background electrolyte (BGE) and applied voltage on chiral separation. Enantiomers of propranolol and metoprolol were baseline resolved using a BGE consisting of 20mM CS and 50/50 (v/v) iso-propanol/phosphate buffer (100mM, pH 7.0) whereas for enantiomers of sertraline, a BGE consisting of 23mM CS and 40/60 (v/v) iso-propanol/phosphate buffer (100mM, pH 7.0) resulted in baseline resolutions.

Enantiomeric selectivity in adsorption of chiral β-blockers on sludge

Adsorption of weakly basic compounds by sludge is poorly understood, although it has important implications on the distribution and fate of such micropollutants in wastewater effluent and sludge. Additionally, many of these compounds are chiral, and it is likely that their interactions with sludge is stereoselective and that the process may be further modified by surfactants that coexist in these systems. Adsorption of (R) and (S)-enantiomers of five commonly used β-blockers, i.e., acebutolol, atenolol, metoprolol, pindolol and propranolol, on sludge was characterized through batch experiments. Stereoselectivity in adsorption increased with decreases in hydrophobicity of the β-blockers. The enantiomeric fraction (EF) of the amount of acebutolol, atenolol and metoprolol sorbed on sludge were 0.27, 0.55 and 0.32, respectively. Thus, Kd values of the (S)-enantiomers of acebutolol and metoprolol were approximately twice that of the (R)-enantiomer, that is, 109 ± 11 and 57 ± 8 L/kg compared to 52 ± 13 and 22 ± 8 L/kg, respectively. There was no statistically significant difference in Kd values of the enantiomers of pindolol and propranolol, suggesting stereoselectivity in adsorption was likely driven by specific polar interactions rather than hydrophobic interactions. The EF value of atenolol decreased from 0.55 ± 0.03 to 0.44 ± 0.04 after modifying the sludge with Triton X 100. These results suggested that surfactants altered adsorption of β-blockers to sludge, likely by forming ion pair complexes that promote hydrophobic interactions with the solid surfaces.

Enantiomeric fractionation as a tool for quantitative assessment of biodegradation: The case of metoprolol

An efficient chiral liquid chromatography high resolution mass spectrometry method has been developed for the determination of metoprolol (MTP) and three of its major metabolites, namely O-desmethylmetoprolol (O-DMTP), α-hydroxymetoprolol (α-HMTP) and metoprolol acid (MTPA) in wastewater treatment plant (WWTP) influents and effluents. The optimized analytical method has been validated with good quality parameters including resolution >1.3 and method quantification limits down to the ng/L range except for MTPA. On the basis of this newly developed analytical method, the stereochemistry of MTP and its metabolites was studied over time in effluent/sediment biotic and sterile microcosms under dark and light conditions and in influents and effluents of 5 different WWTPs. MTP stereoselective degradation was exclusively observed under biotic conditions, confirming the specificity of enantiomeric fraction variations to biodegradation processes. MTP was always biotransformed into MTPA with a (S)-enantiomer enrichment. The results of enantiomeric enrichment pointed the way for a quantitative assessment of in situ biodegradation processes due to a good fit (R2 > 0.98) of the aerobic MTP biodegradation to the Rayleigh dependency in all the biotic microcosms and in WWTPs because both MTP enantiomers followed the same biodegradation kinetic profiles. These results demonstrate that enantiomeric fractionation constitutes a very interesting quantitative indicator of MTP biodegradation in WWTPs and probably in the environment.

Determination of metoprolol enantiomers in human plasma and saliva samples utilizing microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry.

A sensitive, accurate and reliable bioanalytical method for the enantioselective determination of metoprolol in plasma and saliva samples utilizing liquid chromatography-electrospray ionization tandem mass spectrometry was developed and validated. Human plasma and saliva samples were pretreated by microextraction by packed sorbent (MEPS) prior to analysis. A new MEPS syringe form with two inputs was used. Metoprolol enantiomers and internal standard pentycaine (IS) were eluted from MEPS sorbent using isopropanol after removal of matrix interferences using aliquots of 5% methanol in water. Complete separation of metoprolol enantiomers was achieved on a Cellulose-SB column (150 × 4.6 mm, 5 μm) using isocratic elution with mobile phase 0.1% ammonium hydroxide in hexane-isopropanol (80:20, v/v) with a flow rate of 0.8 mL/min. A post-column solvent-assisted ionization was applied to enhance metoprolol ionization signal in positive mode monitoring (+ES) using 0.5% formic acid in isopropanol at a flow rate of 0.2 mL/min. The total chromatographic run time was 10 min for each injection. The detection of metoprolol in plasma and saliva samples was performed using triple quadrupole tandem mass spectrometer in +ES under the following mass transitions: m/z 268.08 → 72.09 for metoprolol and m/z 303.3 → 154.3 for IS. The linearity range was 2.5-500 ng/mL for both R- and S-metoprolol in plasma and saliva. The limits of detection and quantitation for both enantiomers were 0.5 and 2.5 ng/mL respectively, in both matrices (plasma and saliva). The intra- and inter-day precisions were presented in terms of RSD values for replicate analysis of quality control samples and were <5%; the accuracy of determinations varied from 96 to 99%. The method was able to determine the therapeutic levels of metoprolol enantiomers in both human plasma and saliva samples successfully, which can aid in therapeutic drug monitoring in clinical laboratories. Copyright © 2016 John Wiley & Sons, Ltd.

Enantioselective determination of metoprolol and its metabolites in human urine high-performance liquid chromatography with fluorescence detection (HPLC-FLD) and tandem mass spectrometry (MS/MS).

A sensitive, stereoselective assay using solid phase extraction and high-performance liquid chromatography (HPLC) with fluorescence detection (FLD) was developed and validated for the analysis of enantiomers of metoprolol and its metabolites (α-hydroxymetoprolol, O-desmethylmetoprolol). Chiral separation was achieved using a CHIRALCEL OD-RH column, packed with cellulose tris-(3,5-dimethylphenyl-carbamate) stationary phase, employing a mobile phase composed by a mixture of 0.2% diethylamine in water and acetonitrile in gradient elution mode. Linear calibration curves were obtained over the range of 0.025-2.0μg/mL (R(2)>0.994) in urine for both enantiomers of metoprolol and its metabolites with quantitation limit of 0.025μg/mL. Intra and inter-day precision and accuracy were below 15% for both metoprolol and metabolites enantiomers. The recovery of enantiomer of metoprolol and its metabolite was greater than 68.0%, utilizing a SPE procedure. The method was tested with urine quality control samples and human urine fractions after administration of 50mg rac-metoprolol.

Dispersive liquid–liquid microextraction and HPLC to analyse fluoxetine and metoprolol enantiomers in wastewaters

Sample extraction is a major step in environmental analyses due both to the high complexity of matrices and to the low concentration of the target analytes. Sample extraction is usually expensive, laborious, time-consuming and requires a high amount of organic solvents. Actually, there is a lack of miniaturized methodologies for sample extraction and chiral analyses. Here, we developed a dispersive liquid–liquid microextraction (DLLME) to extract the pharmaceuticals fluoxetine and metoprolol, as models of basic chiral compounds, from wastewater samples. Compounds were then analysed by enantioselective high-performance liquid chromatography. We monitored the influence of sample pH, extracting and dispersive solvent and respective volumes, salt addition, extracting and vortexing time. The DLLME method was validated within the range of 1–10 µg L−1 for fluoxetine enantiomers and 0.5–10 µg L−1 for metoprolol enantiomers. Accuracy ranged from 90.6 to 106 % and recovery rates from 54.5 to 81.5 %. Relative standard deviation values lower than 7.84 and 9.00 % were obtained for intra- and inter-batch precision, respectively.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY FOR DETERMINATION OF METOPROLOL ENANTIOMERS IN PHARMACEUTICAL FORMULATIONS

A novel high performance liquid chromatography with fluorescence detector (HPLC-FL) method for determination of metoprolol enantiomers in a pharmaceutical formulation was developed and validated. This study investigated the ultrasound-assisted extraction (UAE) of metoprolol from commercial tablets using methanol as extraction solvent. The separation of enantiomers was successfully carried out with a CHIRALCEL OD-RH column, under isocratic elution mode using 0.05% trifluoroacetic acid and 0.05% diethylamine in water and acetonitrile (80:20, v/v).The chromatographic method was validated in terms of precision, accuracy, detection and quantification limits, linearity and recovery. Calibration curves were linear in the investigated range with correlation coefficient better than 0.9931 while the limit of quantifications was 0.19 µg mL-1 for S(–)-MET and 0.23 µg mL-1 for R(+)-MET. The mean recovery of S(–)-MET and R(+)-MET from tablets were found to be 78.8% and 92.1%, respectively.This method for the direct determination and quantification of metoprolol enantiomers in pharmaceutical formulations is suitable for routine analyses in quality control laboratories and was applied to evaluate for the first time, the presence and the quantities of cited analytes in commercially available formulation.

Clarithromycin as a chiral selector for enantioseparation of basic compounds in nonaqueous capillary electrophoresis.

The first use of macrolide antibiotic clarithromycin (CLM) in nonaqueous media for enantioseparation (partial or baseline) of the following compounds: alprenolol, atenolol, metoprolol, clenbuterol, methoxyphenamine, pindolol, propranolol, sotalol, synephrine, labetalol, and fenoterol is reported. Each analysis took less than 15 min. To find optimal separation conditions, some properties of CLM (adsorption, solubility), as well as the effect of experimental parameters on the enantioseparation of analytes (background electrolyte composition, chiral selector concentration, temperature, and applied voltage) were studied. The best chiral resolution was achieved in methanolic solution of 100 mM citric acid, 10mM NaOH, 240-300 mM H3 BO3 , and 60-75 mM CLM. Using the proposed procedure, adsorption of CLM on the capillary wall was negligible and the repeatability of the migration times (RSD) was as good as 1.6%. For the analysis of propranolol, the linearity was achieved in the concentration range 2.5 × 10(-2) - 3.0 × 10(-1) mg/mL with the LODs (3 × S/N) being equal 2.6 × 10(-3) mg/mL and 2.8 × 10(-3) mg/mL for the first and the second enantiomers, respectively. Linear range for metoprolol enantiomers was 1.0 × 10(-2) -1.6 × 10(-1) mg/mL. The LODs (3 × S/N) were determined as 2.8 × 10(-3) and 3.0 × 10(-3) mg/mL for the first and the second enantiomers, respectively.

Development of a sensitive and rapid method for quantitation of (S)-(−)- and (R)-(+)-metoprolol in human plasma by chiral LC–ESI–MS/MS

A selective, sensitive and high throughput liquid chromatography-tandem mass spectrometry (LC–ESI–MS/MS) method has been developed for separation and quantification of metoprolol enantiomers on a chiral Lux Amylose-2 (250mm×4.6mm, 5μm) column. Solid phase extraction of (S)-(−)- and (R)-(+)-metoprolol and rac-metoprolol-d6 as an internal standard (IS) was achieved on Lichrosep DVB HL cartridges employing 200μL human plasma. Both the analytes were chromatographically separated with a resolution factor of 2.24 using 15mM ammonium acetate in water, pH 5.0 and 0.1% (v/v) diethyl amine in acetonitrile (50:50, v/v) as the mobile phase within 7.0min. The precursor→product ion transitions for the enantiomers and IS were monitored in the multiple reaction monitoring and positive ionization mode. The method was validated over the concentration range of 0.500–500ng/mL for both the enantiomers. Matrix effect was assessed by post-column analyte infusion experiment and the mean extraction recovery was greater than 94.0% for both the enantiomers at all quality control levels. The stability of analytes was evaluated in plasma and whole blood under different storage conditions. The method was successfully applied to a clinical study in 14 healthy volunteers after oral administration of 200mg metoprolol tablet under fasting conditions. The assay reproducibility is shown by reanalysis of 68 incurred samples. The suitability of the developed method was assessed in comparison with different chromatographic methods developed for stereoselective analysis of metoprolol in biological matrices.

Stereoselective Determination of Metoprolol and its Metabolite α‐Hydroxymetoprolol in Plasma by LC‐MS/MS: Application to Pharmacokinetics during Pregnancy

Metoprolol is available for clinical use as a racemic mixture. The S-(-)-metoprolol enantiomer is the one expressing higher activity in the blockade of the β(1)-adrenergic receptor. The α-hydroxymetoprolol metabolite also has activity in the blockade of the β(1)-adrenergic receptor. The present study describes the development and validation of a stereoselective method for sequential analysis of metoprolol and of α-hydroxymetoprolol in plasma using high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS). 1-ml aliquots of plasma were extracted with dichloromethane : diisopropyl ether (1:1, v/v). Metoprolol enantiomers and α-hydroxymetoprolol isomers were separated on a Chiralpak AD column (Daicel Chemical Industries, New York, NY, USA) and quantitated by LC-MS/MS. The limit of quantitation obtained was 0.2 ng of each metoprolol enantiomer/ml plasma and 0.1 ng/ml of each α-hydroxymetoprolol isomer/ml plasma. The method was applied to the study of kinetic disposition of metoprolol in plasma samples collected up to 24 h after the administration of a single oral dose of 100-mg metoprolol tartrate to a hypertensive parturient with a gestational age of 42 weeks. The clinical study showed that the metoprolol pharmakokinetics is enantioselective, with the observation of higher area under the curve (AUC)(0-∞) values for S-(-)-metoprolol (AUC(S-(-)) /AUC(R-(+)) = 1.81) and the favoring of the formation of the new chiral center 1'R of α-hydroxymetoprolol (AUC(0-∞) (1'R/1'S) = 2.78).

Chiral analysis of metoprolol and two of its metabolites, α-hydroxymetoprolol and deaminated metoprolol, in wastewater using liquid chromatography–tandem mass spectrometry

A LC–MS/MS method for the chiral separation of metoprolol and two of its main metabolites, α-hydroxymetoprolol (α-OH-Met) and deaminated metoprolol (COOH-Met), in environmental water samples has been developed. The target bases, metoprolol and α-OH-Met, as well as the acidic metabolite (COOH-Met) were extracted from water samples by a solid phase extraction method employing Oasis HLB cartridges. The extraction recoveries were ≥73% for all compounds in surface water. Four different types of chiral stationary phases were investigated for the separation of the eight stereoisomers of metoprolol and its metabolites, Chiralcel OD-H, Chirobiotic V, Chiral AGP and Chiral CBH. In the final method, the enantiomers of metoprolol and four stereoisomers of α-OH-Met were separated using Chiral CBH, the enantiomers of COOH-Met were separated employing Chiral AGP. The analytes were detected in SRM mode by triple quadrupole mass spectrometry. The method was applied for the chiral analysis of the analytes in treated wastewater samples from Uppsala, Sweden. The enantiomers and diastereoisomers of α-OH-Met were detected and analyzed in the samples. The concentrations of the three first eluting stereoisomers of α-OH-Met were between 54 and 61pM. Interestingly, the last eluting stereoisomer was found to be present at a concentration of 151pM at the same sampling occasion. This is, to the best of the authors’ knowledge, the first time the stereoisomers of α-OH-Met have been detected in wastewater samples. The enantiomers of metoprolol were determined to be 1.77 and 1.86nM in the same matrix. The enantiomers of COOH-Met were not detected above the method detection limit (42pM) in treated wastewater samples. The developed LC–MS/MS methods were validated in wastewater samples.

Evaluation of clarithromycin lactobionate as a novel chiral selector for enantiomeric separation of basic drugs in capillary electrophoresis

Nowadays, macrocyclic antibiotics are presenting an increasing number of enantioseparation applications. The macrocyclic antibiotics used as chiral selectors in capillary electrophoresis (CE) include the ansamycins and the glycopeptides. The macrolides, another important class of macrocyclic antibiotics, have been reported as a new type of chiral selectors recently. In this study, clarithromycin lactobionate (CL), belonging to the group of macrolide antibiotics, was first investigated for its potential as a novel chiral selector in CE for enantiomeric separation of several basic drugs. As observed, CL allowed excellent separation of the enantiomers of metoprolol, atenolol, propranolol, bisoprolol, esmolol, ritodrine, and amlodipine, as well as partial enantioresolution of labetalol and nefopam. In addition, CL possesses advantages such as high solubility and low viscosity in the solvent and very weak UV absorption. In the course of this study, it was found that both migration times and enantioseparation of the basic drugs were influenced by several experimental parameters, e.g. selector concentration, the composition and pH of the BGE, the type and concentration of organic modifier, and applied voltage. Thus, the effects of these factors were systematically investigated, and satisfactory enantioseparations of the studied drugs were achieved at the buffer pH range of 7.3-7.5 using 12.5 mM borax buffer with 50% v/v methanol, 60 mM CL, and 20 kV applied voltage. Moreover, comparison of the influences of the studied parameters was further investigated by means of Statistical Product and Service Solutions (SPSS) in this article.

Liquid chromatographic resolution of the enantiomers of metoprolol and carvedilol in pharmaceutical formulations by use ofMarfey’sreagent and its variants

A simple and rapid method has been established for indirect separation of the enantiomers of (R,S)-metoprolol and (R,S)-carvedilol by reversed-phase TLC. Beta blockers derivatized with 1-fluoro-2,4-dinitrophenyl-5-l-alanine amide (Marfey’s reagent, FDNP-l-Ala-NH2) and its six structural variants (FDNP-l-Phe-NH2, FDNP-l-Val-NH2, FDNP-l-Pro-NH2, FDNP-l-Leu-NH2, FDNP-l-Met-NH2, and FDNP-d-Phg-NH2) were spotted on precoated plates. (R,S)- Metoprolol and (R,S)-carvedilol were isolated from pharmaceutical dosage forms and purified. The diastereomers were separated most effectively by use of mobile phases containing acetonitrile and triethylamine-phosphate buffer (50 mM, pH 5.5). The results obtained by use of Marfey’s reagent were compared with those obtained by use of the other variants. The effects of buffer concentration, pH, and concentration of organic modifier were studied.