Chiralpak IC Research Articles

Thermodynamic evaluation of immobilized cellulose tris(3,5-dichlorophenylcarbamate) as a stationary phase for liquid chromatographic separation of darunavir enantiomers.

Liquid chromatographic separation of darunavir (DRV) enantiomers was studied on Chiralpak IC column containing immobilized cellulose tris(3,5-dichlorophenylcarbamate) using a variety of mobile phase solvents at different temperatures. The separations were accomplished under normal phase conditions using different compositions of n-hexane, organic modifier (2-propanol, ethanol or 1-propanol) and diethyl amine (0.1%) as mobile phase solvents. The effect of volume and nature of organic modifier and column temperature on retention, separation and resolution were studied. Van't Hoff plots (ln k' vs 1/T) were drawn from the chromatographic retention data to calculate to apparent thermodynamic parameters and explain the interactions between the DRV enantiomers and cellulose tris(3,5-dichlorophenylcarbamate) immobilized on silica.

The Chiral Separation and Enantioselective Degradation of the Chiral Herbicide Napropamide

The chiral pesticide enantiomers often have different toxic effects and environmental behaviors, which suggests that the risk assessments should be on an enantiomeric level. In this work, the chiral separation of the napropamide enantiomers and the stereoselective degradation in tomato, cucumber, rape, cabbage, and soil were investigated. Napropamide enantiomers could be separated absolutely by high-performance liquid chromatography (HPLC) using a Chiralpak IC column with a resolution factor of 11.75 under the optimized condition. Solid phase extraction (SPE) was used for cleanup of the enantiomers in the vegetable samples. The residue analysis method was validated. Good linearities (R(2) = 0.9997) and recoveries (71.43% -97.64%) were obtained. The limits of detection (LOD) were 0.05 mg/kg in soil and 0.20 mg/kg in vegetables. The results of degradation showed that napropamide dissipated rapidly in vegetables with half-lives of only 1.13-2.21 days, but much more slowly in soil, with a half-life of 11.95 d. Slight stereoselective degradation of the two enantiomers was only observed in cabbage, with enantiomeric fraction (EF) = 0.46, and there was no enantioselectivity in the other vegetables. The degradation of napropamide in the five matrixes was fast, and there was no enantioselectivity.

Chiral liquid chromatography resolution and stereoselective pharmacokinetic study of pioglitazone enantiomers in rats

A selective chiral high performance liquid chromatographic (HPLC) method was developed and validated to separate and quantify the pioglitazone enantiomers in rat plasma. After extraction of the plasma samples with ethyl acetate, the separation of pioglitazone enantiomers and internal standard (I.S., dexamethasone acetate) was achieved on a cellulose tris (3,5-dichlorophenylcarbamate) column known as Chiralpak IC with a mobile phase of hexane-isopropanol (70:30, v/v) at a flow rate of 1.0mL/min. The ultraviolet (UV) detection wavelength was set at 225nm. Baseline separation of pioglitazone enantiomers and I.S., free from endogenous interferences, was achieved in less than 25min. Ratio of peak area of each enantiomer to I.S. was used for quantification of plasma samples. Linear calibration curves were obtained over the range of 0.25-50μg/mL in plasma for both enantiomers (R(2)>0.9990) with quantitation limit of 0.25μg/mL. The mean extraction recoveries were 82.37-91.38% for pioglitazone enantiomers and 95.76% for I.S. from rat plasma. The mean relative error (R.E. %) of accuracy and the mean relative standard deviation (R.S.D. %) of intra-day and inter-day precision for both enantiomers were <10%. The method was validated with accuracy, precision, recovery and stability and used to determine the pharmacokinetics of pioglitazone enantiomers, after a single oral administration of racemic pioglitazone (30mg/kg). The differences between the pharmacokinetic parameters Cmax, AUC0-24, AUC0-∞, CL/F of (+)-pioglitazone and (-)-pioglitazone were significant, suggesting that the disposition of pioglitazone in rats may be enantioselective. Moreover, the plasma levels of (+)- and (-)-pioglitazone in female rats were apparently higher than that in male rats, respectively.

RESOLUTION OF RACEMIC γ-SUBSTITUTED BUTENOLIDE DERIVATIVES USING A POLYSACCHARIDE TYPE STATIONARY PHASE BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

The enantioseparation by immobilized polysaccharide-based chiral stationary phases has pronounced advantages due to its enhanced efficiency and universal solvent resistance. The newly synthesized γ-substituted butenolide derivatives, which showed good inhibitory activity against wide range of fungi, were successfully resolved on cellulose tris(3,5-dichlorophenylcarbamate) chiral stationary phase (Chiralpak IC) by high performance liquid chromatography (HPLC). The effects of mobile phase composition and column temperature were studied. The good resolution was achieved using a mobile phase composition of hexane and ethanol. Under optimal conditions, the resolutions of enantiomers of five compounds were 1.96, 1.66, 1.93, 1.72, and 2.03, respectively. For the butenolides derivatives, π–π interaction contributes to the retention rather than selectivity, resolution was dramatically changed corresponding to variation of ethanol content in the mobile phase. This suggests that the dominant chiral recognition is from hydrogen bonding interactions. With regard to the structure of the analytes, bulky R1 substituents and electron deficiency R2 substituents appear to favor stereoselective interaction.

Pharmaceutical-enantiomers resolution using immobilized polysaccharide-based chiral stationary phases in supercritical fluid chromatography

Since their introduction on the market the applicability of immobilized polysaccharide-based chiral stationary phases in high-performance liquid chromatography has been thoroughly investigated. These immobilized phases have the benefit to be applicable with a wide range of modifiers, potentially extending the application range of the polysaccharide-based stationary phases. Because an increasing number of stationary phases are being introduced in the field of chiral chromatography it is important to evaluate their enantioselectivity in different techniques in order to get an idea about their applicability. In this study, three immobilized chiral polysaccharide-based stationary phases (Chiralpak IA, IB, and IC) are evaluated in supercritical fluid chromatography (SFC) with a test set of pharmaceutical racemates. This is done in a three-fold manner: their performance is evaluated (1) using traditional modifiers, (2) using mixtures of atypical modifiers, and (3) the results were compared to those on coated stationary phases with an equivalent chiral selector. To get a visual overview of the enantioselective patterns of the different chromatographic systems (mobile and stationary phase combinations), a Principal Component Analysis is performed, which allows determining the (dis)similarity between individual systems. To assess the complementarity cumulative success rates are determined. The immobilized chiral stationary phases prove to yield high cumulative success rates.

Chiral separation of six tetralone derivative enantiomers using immobilized cellulose chiral stationary phase

A high performance liquid chromatographic method (HPLC) was developed for the chiral separation of six α-aryl tetralone derivatives, using a Chiralpak IC column. The factors influencing the chiral separation including the type and concentration of organic modifier, column temperature and flow rate were investigated. The results showed that high enantiomeric separation can be obtained with isopropanol as modifier for the six compounds. The thermodynamic study indicated that the enantioseparation was enthalpically driven and showed that low column temperature was beneficial to separation. Complete separation of compound I was achieved with a binary solvent mixture of n-hexane-isopropanol (90 :10, v/v) as the recommended mobile phase. The compounds II , II and IV were separated with the mobile phase of the mixture of n-hexane-isopropanol (99:1, v/v) and the compound V was separated with the mixture of n-hexane-isopropanol (85:15, v/v). The compound VI was separated with the mixture of n-hexane-isopropanol (80:20, v/v). The column temperature was 25 °C, and the flow rate was 1. 0 mL/min. The six tetralone derivative enantiomers were separated on a chiral stationary phase of Chiralpak IC by HPLC. The column has high enantiomeric selectivity to the six tetralone derivative enantiomers.

Evaluation of non-conventional polar modifiers on immobilized chiral stationary phases for improved resolution of enantiomers by supercritical fluid chromatography

An evaluation of the use of non-conventional polar modifiers for the supercritical fluid chromatographic separation of enantiomers on immobilized chiral stationary phases is presented. The resolution of a group of nine commercially available racemates is studied on the Chiralpak IA, IB, IC, ID, IE, and IF chiral stationary phases using CO2-based eluents containing non-conventional polar modifiers such as dichloromethane, chloroform, tetrahydrofuran, 2-methyl tetrahydrofuran, methyl tert-butyl ether, cyclopentyl methyl ether, acetone, ethyl acetate, toluene, 2,2,2-trifluoroethanol, and N,N-dimethylformamide. Screening experiments and method development for the commercial racemates on the immobilized columns with the non-conventional solvents demonstrated an ability to adjust the retention and improve resolution. From these results we were able to assign a general eluotropic relationship between the non-conventional solvents and methanol. A general ability to selectively adjust chromatographic retention while improving analyte solubility can lead to improved preparative chromatographic performance.

Optimization of the HPLC enantioseparation of 3,3′-dibromo-5,5′-disubstituted-4,4′-bipyridines using immobilized polysaccharide-based chiral stationary phases

The HPLC enantioseparation of nine atropisomeric 3,3',5,5'-tetrasubstituted-4,4'-bipyridines was performed in normal and polar organic (PO) phase modes using two immobilized polysaccharide-based chiral columns, namely, Chiralpak IA and Chiralpak IC. The separation of all racemic analytes, the effect of the chiral selector, and mobile phase (MP) composition on enantioseparation and the enantiomer elution order (EEO) were studied. The beneficial effect of nonstandard solvents, such as tetrahydrofuran (THF), dichloromethane (DCM), and methyl t-butyl ether on enantioseparation was investigated. All selected 4,4'-bipyridines were successfully enantioseparated on Chiralpak IA under normal or PO MPs with separation factors from 1.14 to 1.70 and resolutions from 1.3 to 6.5. Two bipyridines were enantioseparated at the multimilligram level on Chiralpak IA. Differently, Chiralpak IC was less versatile toward the considered class of compounds and only five bipyridines out of nine could be efficiently separated. In particular, on these columns, the ternary mixture n-heptane/THF/DCM (90:5:5) as MP had a positive effect on enantioseparation. An interesting phenomenon of reversal of the EEO depending on the composition of the MP for the 3,3'-dibromo-5,5'-bis-(E)-phenylethenyl-4,4'-bipyridine along with an exceptional enantioseparation for the 3,3'-dibromo-5,5'-bis-ferrocenylethynyl-4,4'-bipyridine (α = 8.33, R(s) = 30.6) were observed on Chiralpak IC.

Analytical and semipreparative separation of 25 (R/S)‐spirostanol saponin diastereomers using supercritical fluid chromatography

Spirostanol saponins are a class of steroidal saponins with many pharmacological activities. The structural complexity of the spirostanol saponins presents a daunting challenge in separating their 25 R/S diastereomers. Using two CHIRALPAK IC columns coupled in series, six 25 (R/S)-spirostanol saponin diastereomers from the Trigonella foenum-graecum L. seed were successfully separated using supercritical fluid chromatography (SFC) for the first time. In addition, three 25 (R/S)-spirostanol saponin diastereomers were isolated into their respective individual isomers. The structures of the isolated isomers were unambiguously confirmed by NMR analysis. The SFC method development strategy and its associated underlying principles presented in this paper are generally applicable. SFC is a viable addition to the natural product research toolbox, especially for stereoselective analysis and purification.

Enantiomeric separation of proton pump inhibitors on new generation chiral columns using LC and supercritical fluid chromatography

The enantioselectivity of proton pump inhibitors, namely, omeprazole, lansoprazole, rabeprazole, pantoprazole, tenatoprazole, and ilaprazole were studied using new generation chiral packing materials: CHIRALPAK IA, CHIRALPAK IB, and CHIRALPAK IC. Two versatile techniques, HPLC and supercritical fluid chromatography (SFC) were used in this study. CHIRALPAK IC has shown superior selectivity under both LC and SFC conditions, whereas CHIRALPAK IA has shown good selectivity in SFC when compared to LC under primary screening conditions. The chiral recognition ability in LC and SFC modes were found to be in the order CHIRALPAK IC > CHIRALPAK IA > CHIRALPAK IB. In addition to diode array detection, chiral detection was carried out using a laser polarimeter and the elution orders were found to be the same in both LC and SFC elution modes. Mobile phase modifiers and column temperature effects were also studied. In SFC, modifiers (cosolvent) elution strength was found to be in the order ethanol > methanol > 2-propanol > acetonitrile. In both LC and SFC, a decrease in retention and increase in resolution with an increase in temperature was noticed for all the proton pump inhibitors.

Separation of mandelic acid and its derivatives with new immobilized cellulose chiral stationary phase

A new liquid chromatographic method has been developed for the chiral separation of the enantiomers of mandelic acid and their derivatives 2-chloromandelic acid, 4-hydroxymandelic acid, 4-methoxymandelic acid, and 3,4,5-trismethoxymandelic acid. The enantiomers were separated by a CHIRALPAK(®) IC (250 mm×4.6 mm, 5 μm). Mandelic acid, 4-methoxymandelic acid, and 3,4,5-trismethoxymandelic acid were baseline resolved (resolution factor (RS)=2.21, RS=2.14, and RS=3.70, respectively). In contrast, the enantioselectivities between CHIRALPAK(®) IC and 2-chloromandelic acid and 4-hydroxymandelic acid investigated were low. By comparing the chromatographs of mandelic acid enantiomers and mandelic acid spiked with (R)-mandelic acid, it was determined that the first effluent was (R)-mandelic acid.

A New Chiral Residue Analysis Method for Triazole Fungicides in Water Using Dispersive Liquid‐Liquid Microextraction (DLLME)

A rapid, simple, reliable, and environment-friendly method for the residue analysis of the enantiomers of four chiral fungicides including hexaconazole, triadimefon, tebuconazole, and penconazole in water samples was developed by dispersive liquid-liquid microextraction (DLLME) pretreatment followed by chiral high-performance liquid chromatography (HPLC)-DAD detection. The enantiomers were separated on a Chiralpak IC column by HPLC applying n-hexane or petroleum ether as mobile phase and ethanol or isopropanol as modifier. The influences of mobile phase composition and temperature on the resolution were investigated and most of the enantiomers could be completely separated in 20 min under optimized conditions. The thermodynamic parameters indicated that the separation was enthalpy-driven. The elution orders were detected by both circular dichroism detector (CD) and optical rotatory dispersion detector (ORD). Parameters affecting the DLLME performance for pretreatment of the chiral fungicides residue in water samples, such as the extraction and dispersive solvents and their volume, were studied and optimized. Under the optimum microextraction condition the enrichment factors were over 121 and the linearities were 30-1500 µg L(-1) with the correlation coefficients (R(2)) over 0.9988 and the recoveries were between 88.7% and 103.7% at the spiking levels of 0.5, 0.25, and 0.05 mg L(-1) (for each enantiomer) with relative standard deviations varying from 1.38% to 6.70% (n = 6) The limits of detection (LODs) ranged from 8.5 to 29.0 µg L(-1) (S/N = 3).

Chiral liquid chromatography resolution and stereoselective pharmacokinetic study of indapamide enantiomers in rats

This investigation describes a precise and accurate stereoselective HPLC method for the simultaneous determination of indapamide enantiomers in whole blood to follow its pharmacokinetics in rats up to 24h after single oral dosing. Enantiomeric resolution was achieved on a cellulose tris (3,5-dichlorophenylcarbamate) column known as Chiralpak IC, with UV detection at 240nm, and the mobile phase consisted of n-hexane and isopropanol (70:30, v/v). Using the chromatographic conditions described, indapamide enantiomers were well resolved with a resolution factor (Rs) of at least 2.0 and with retention times of 19.2 and 23.3min, respectively. Linear responses (r>0.999) were observed over the range of 0.05-50μg/mL of indapamide enantiomers, with quantitation limit of 0.05μg/mL. The mean relative standard deviation (RSD) of within-day precision and accuracy of the drug were <10%. The mean extraction efficiency was greater than 86% for each enantiomer. The assay method shows good specificity to indapamide enantiomers, and it could be successfully applied to its pharmacokinetic studies and to therapeutic drug monitoring.

Chiral separation of amides using supercritical fluid chromatography

Nine amide derivatives bearing α-stereocenters as well as different substitutions on the amide nitrogen were synthesized via an n-propanephosphonic acid cyclic anhydride (T3P)-mediated coupling, and their enantiomeric pairs were separated using supercritical fluid chromatography (SFC). Five polysaccharide-based chiral stationary phases (CSPs), Chiralcel OD-H, and OJ-H, and Chiralpak AD-H, AS-H and IC columns were explored for the chiral separation of these compounds. None of the compounds could be resolved on all five columns, and no single column could separate all nine pairs of enantiomers. Comparatively, the IC and OD-H columns showed the best results for this group of amides, yielding baseline separations for eight of nine pairs. The type of polar functional group and aromatic substitution in the CSPs and the substitutions on the amide nitrogen had a significant impact on the enantiomeric resolution of the compounds in the interaction between the analyte and the stationary phases. The potential separation mechanism and the effect of substitutions in the CSPs and amide solutes on the separation are discussed. The effects of the organic modifiers, modifier composition, mobile phase additives, and temperature were investigated for the separation of these amides on the IC or the OD-H column. Baseline resolution was achieved under optimized chromatographic conditions using an IC or an OD-H column. Linearity, reproducibility, and limit of quantitation were also demonstrated for the compound 9. Approximately three-fold improvement in signal-to-noise was observed using a SFC system with better instrument design.

Access to Enantiomerically Pure cis‐ and trans‐β‐Phenylproline by High‐Performance Liquid Chromatography Resolution

The preparation of all four stereoisomers of the proline analog that bears a phenyl group attached to the β carbon either cis or trans to the carboxylic acid (cis- and trans-β-phenylproline, respectively) has been addressed. The methodology developed allows access to multigram quantities of the target amino acids in enantiomerically pure form and suitably protected for use in peptide synthesis. Racemic precursors of cis-β-phenylproline and trans-β-phenylproline were prepared from easily available starting materials and subjected to high-performance liquid chromatography enantioseparation. Semipreparative columns (250 × 20 mm) containing chiral stationary phases based on amylose (Chiralpak IA) (Daicel-Chiral Technologies Europe, Illkirch, France) or cellulose (Chiralpak IC) were used respectively for the resolution of the cis- and trans-β-phenylproline precursors.

Absolute Configuration and Enantiodifferentiation of a Hemicryptophane Incorporating an Azaphosphatrane Moiety

The hemicryptophane racemate (±)-1 was optically resolved by semipreparative HPLC on Chiralpak IC column. The absolute configuration of each isolated enantiomer was established from the analysis of their electronic circular dichroism spectra. Enantiodifferentiation of the chiral cationic cage (±)-1 was evidenced in solution using Δ-TRISPHAT as chiral solvating agent, and the diastereomeric associations were observed in (1)H and (31)P NMR spectra.

아미노산 에스테르의 벤조피논 이민 유도체의 액체 크로마토그래피의 광학분리

A convenient liquid chromatographic enantiomer separation of several <TEX>${\alpha}$</TEX>-amino acid esters as benzophenone Schiff base derivatives on covalently immobilized chiral stationary phases (CSPs) derived from polysaccharide derivatives was developed. The benzophenone imine derivatives of <TEX>${\alpha}$</TEX>-amino acid esters were readily prepared by stirring benzophenone imine and the <TEX>${\alpha}$</TEX>-amino acid ester hydrochloride salts in 2-propanol. The chromatographic conditions used on all CSPs were 0.5% or 5% 2-propanol/hexane (V/V) as the mobile phases at 1 mL/min of flow rate and UV 254 nm detection. The performance of Chiralpak IC among all CSPs was superior to that of the other CSPs for resolution of benzophenone imine derivatives of <TEX>${\alpha}$</TEX>-amino acid esters. It is expected that the developed analytical method will be useful for enantiomer resolution of other <TEX>${\alpha}$</TEX>-amino acid esters as benzophenone Schiff base derivatives.

A Validated LC Method for the Determination of the Enantiomeric Purity of Aliskiren Hemifumarate in Bulk Drug Samples

High-performance liquid chromatography enantioseparation of aliskiren hemifumarate was accomplished on an immobilized-type Chiralpak IC chiral stationary phase under both polar organic and reversed-phase modes. A simple analytical method was developed and validated using a mixture of acetonitrile-n-butylamine 100:0.1 (v/v/) as a mobile phase with a flow rate maintained at 1.0 mL/min. Ultraviolet detection was carried out at 228 nm. Resolution between the two enantiomers was greater than 3.0. This method was capable of detecting the R-isomer to a level of 0.2 μg/mL. The method was validated as per International Conference on Harmonization guidelines and found to be robust. The method is very useful for routine evaluation of the quality of aliskiren hemifumarate in bulk drug manufacturing units.

A convenient method for the enantiomeric separation of α-amino acid esters as benzophenone imine Schiff base derivatives

A convenient liquid chromatographic method for the separation of α-amino acid esters as benzophenone Schiff base derivatives on coated chiral stationary phases (CSPs) (Chiralcel OD-H, Chiralcel OD, Chiralpak AD-H, Chiralpak AD, and Chiralpak AS) or covalently immobilized CSPs (Chiralpak IA, Chiralpak IB, and Chiralpak IC) derived from polysaccharide derivatives is described. Benzophenone imine derivatives of α-amino acid esters were readily prepared by stirring benzophenone imine and the hydrochloride salts of α-amino acid esters in 2-propanol. The chromatographic separations were conducted at a flow rate 1.0 mL/min and a detection wavelength of 254 nm; 0.5% 2-propanol/hexane (v/v) was used on CSPs. In general, the resolution of Chiralpak IC was superior to those of the other CSPs. In addition, the resolutions of other arylimine derivatives of α-amino acid esters and the effects of different mobile phases on the enantiomeric separation of α-amino acid esters as benzophenone imine derivatives on Chiralpak IC were investigated.

Recent Trends in Chiral Separations on Immobilized Polysaccharides CSPs

Polysaccharide CSPs are recognized widely in chiral chromatography but the introduction of immobilized phases (Chiralpak IA, Chiralpak IB and Chiralpak IC columns) is a remarkable achievement. The immobilized CSPs can be used with organic, normal and reversed phase modes; even with prohibited solvents too (tetrahydrofuran, chlorofom, dichloromethane, acetone, 1,4-dioxane, ethylacetate, and certain other ethers). Their susceptibilities to work with a wide range of solvents have increased the range of applications including chiral recognition mechanisms. Besides, these are also useful for monitoring the progress of stereo-specific reactions; normally need prohibited solvents. The present review describes the various aspects of commercial available immobilized chiral columns. Attempts have been made to discuss immobilized polysaccharides CSPs, immobilized vs coated CSPs, comparison of immobilized CSPs, method development, optimization, chiral recognition mechanism and applications. The chiral recognition capabilities of commercial columns were in the order of Chiralpak IA > Chiralpak IB > Chiralpak IC columns; but complimentary to each other. Of course, these CSPs are not fully developed and need more advancements and applications. Definitely, the future of immobilized CSPs is quite better. Hopefully, in the coming years they will be the choice of the chromatographers for chiral separations in liquid chromatography.