Enantiomer separation of phenyllactic acid by HPLC with Hp-β-cyclodextrin as chiral mobile phase additive

In our current research work, a sensitive, specific, and economic HPLC method has been developed for the separation of phenyllactic acid (PLA) enantiomers. The effects of cyclodextrin (CD) type, column temperature, buffer pH, methanol content and CD concentration on enantioselective separation were investigated. Baseline chromatographic separation was achieved on an Inertsil ODS-SP (150 × 4.6 mm, i.d. 5 μm) column with HP-β-CD as chiral mobile phase additive. The LOD and LOQ for d-phenyllactic acid were 0.3 and 0.7 μg/mL, respectively. A good linear relationship was obtained in the concentration range of 0.71–5.13 μg/mL with r² >0.999 for d-PLA. The percentage recovery of the d-PLA ranged from 94.1 to 103.2 in l-PLA. This method is simple and cost-saving, and could be easily applied for chiral discrimination and determination of the racemic PLA in an enantioselective study in quality control laboratory.     

Chromatographic and spectroscopic studies on the chiral recognition of sulfated β-cyclodextrin as chiral mobile phase additive: Enantiomeric separation of a chiral amine

A fast enantiomeric separation of a chiral aromatic amine was achieved, using ultra high pressure liquid chromatography and highly sulfated beta-cyclodextrin (S-β-CD) as a chiral additive in the mobile phase. The stationary phase consisted of a core–shell support with a particle size of 2.7 μm. Under these conditions the base-line separation was obtained within 2.5 min. The influence of the concentration of the additive, along with the thermodynamics of the separation, was studied. Vibrational circular dichroism (VCD) spectroscopy was applied to assess the absolute configuration of the two enantiomeric analytes, as well as the interaction of these enantiomers with the S-β-CD. The VCD results revealed that S-β-CD undergoes a temperature-induced conformational change. Further, VCD experiments indicate that the interactions of the two enantiomers with the S-β-CD occur through an inclusion of the aromatic part of the analyte, as well as through electrostatic interaction between the protonated amine and the sulfate groups located at the narrow part of the S-β-CD. Molecular mechanics calculations performed according to the VCD results are consistent with experimental data, providing further evidence of these interactions.     

A β-cyclodextrin covalent organic framework used as a chiral stationary phase for chiral separation in gas chromatography

Chiral covalent organic frameworks(CCOFs) featuring chirality, stability, and good porosity have attracted a considerable amount of attention due to their important applications, such as asymmetric catalysis, chiral separation, and chiral recognition. In this study, a β-cyclodextrin(β-CD) covalent organic framework(β-CD-COF) diluted with polysiloxane OV-1701 was explored as a novel chiral stationary phase(CSP) for gas chromatography(GC) separation of racemates. The β-CD-COF coated capillary colu...     

Investigation on chiral capillary columns and their application in separation of enantiomers

Six chiral diamide stationary phases (CSPs), namely N-(3-carbobenzoxypropionyl)-L-Val-tert-butylamide (CSP-1), N-undecenoyl-L-Val-S-α-phenylethylamide (CSP-2), N-undecenoyl-L-Val-R-α-phenylethylamide (CSP-3), OV-225-L-Val-tert-butylamide (CSP-4), XE-60-L-Val-tert-butylamide (CSP-5) and polycyanoethyl vinyl siloxane-L-Val-tert-butylamide (CSP-6), were inves-tigated and CSP-6 was crosslinked within narrow bore (70 μm) fused silica capillary columns. Theseparation of amino acid enantiomers on this narrow bore column by gas chromatography (GC) isillustrated.     

Enantioseparation of five racemic N-alkyl drugs by reverse phase HPLC using sulfobutylether-β-cyclodextrin as a chiral mobile phase additive

Analytical enantioseparations of five N-alkyl drugs, fluoxetine hydrochloride, labetalol, venlafaxine hydrochloride, trans-paroxol, and atropine sulfate, were investigated by reverse phase high-performance liquid chromatography with sulfobutylether-β-cyclodextrin as chiral mobile phase additive. Effects of various factors such as composition of mobile phase, concentration of cyclodextrins, and column temperature on retention and enantioselectivity were studied. Apparent formation constant between methanol, acetonitrile, and sulfobutylether-β-cyclodextrin were determined to be 2.90 × 10⁻³ and 1.00 × 10⁻⁴ L mmol⁻¹ under 25°C using UV-spectrophotometry. Van't Hoff plots were used to investigate thermodynamic parameters for enantiomers–stationary phase interaction and formation of inclusion complex. Two retention models were employed individually for evaluation of inclusion complexation between five racemates and sulfobutylether-β-cyclodextrin. The second model with complex adsorption was more accord with the retention behavior of fluoxetine hydrochloride, labetalol, and venlafaxine hydrochloride enantiomers, while the first model was more consistent with the retention behaviors of trans-paroxol and atropine sulfate. In the selected mobile phase, stoichiometric ratio for both of inclusion complex was found to be 1:1.     

Chiral separation on achiral stationary phases with different functionalities using β-cyclodextrin in the mobile phase and application to bioanalysis and coupled columns

Summary -cyclodextrin was used in the mobile phase as chiral selector for separating the enantiomers of terbutaline, chlorthalidone and oxazepam. The effect on chiral resolution using e.g. hydrophobic, polar or cation exchanging stationary phases was investigated. Both the chiral separation factor and retention level were affected by the concentration of methanol and -cyclodextrin. The stationary phase had no effect on the chiral separation only on the level of retention. By tuning the concentration of -cyclodextrin and methanol in the mobile phase chiral separation could be obtained on most stationary phases. By changing the stationary phase while adjusting the mobile phase composition to maintain the chiral selectivity, improvements of the selectivity towards e.g. endogenous compounds can be obtained when separating enantiomers in complex matrixes as biological fluids. Further improvement on selectivity can be obtained if coupled columns are used. This is examplified for separation of chlorthalidone and terbutaline enantiomers in biological fluids by coupling an achiral column to another achiral column and using a mobile phase containing -cyclodextrin on the last column.     

A simple method for the separation of (6R)- and (6S)-5,6,7,8-tetrahydrofolic acid by reversed-phase HPLC with hydroxypropyl-β-cyclodextrin as the mobile phase additive

(6R)- and (6S)-5,6,7,8-tetrahydrofolic acid were resolved by reversed-phase HPLC on a C-18 column with hydroxypropyl-??-cyclodextrin (HP-??-CD) in the mobile phase. As the concentration of HP-??-CD increased from 0 to 45?mM, resolution increased and retention times decreased dramatically. The influence of different mobile phase pH, column temperature, and some other factors were evaluated, and we obtained the optimal HPLC separation conditions.     

A comparison of phosphated and sulfated β-cyclodextrins as chiral selectors for capillary electrophoresis

The enantioseparation capabilities of three different functionalized β-cyclodextrins, two sulfated β-cyclodextrins with 4 and 15 nominal degrees of substitution and a phosphated β-cyclodextrin with 8 degrees of substitution, were compared. While anodic detection was used with both sulfated cyclodextrins, the phosphated cyclodextrin required cathodic detection suggesting either lower ionization of the phosphated cyclodextrin or generally lower affinity of the analytes for the phosphated cyclodextrin. The effects of several experimental parameters were evaluated with respect to enantioseparation. The degrees of substitution of the cyclodextrin, pH of the background electrolyte as well as the concentration of the functionalized β-cyclodextrin, each had a significant influence on the successful enantiomeric separation of the chiral drugs investigated.     

Chromatographic study of four sesquiterpenoids in volatile oil of Curcumae Rhizoma on reverse phase stationary phase with methyl-β-cyclodextrin as mobile additive

Abstract

The elution behavior of four sesquiterpenoids in volatile oil of Curcumae Rhizoma on reverse-phase high-performance liquid chromatography with methyl-β-cyclodextrin as mobile phase additive was studied, including germacrone, curzerene, furanodiene, and β-elemene. Stoichiometric ratio and apparent formation constants of inclusion complex formed by methyl-β-cyclodextrin and each analyte were calculated by varying the concentration of the additive in the mobile phase composed of methanol and water (90:10, v/v), in which the association constant for inclusion complex formed by the organic modifier methanol and methyl-β-cyclodextrin was also determined. Results showed that the stoichiometric ratio of all the inclusion complex was 1:1 when 0–9?mmol L^?1 of methyl-β-cyclodextrin was added in the mobile phase. Unusual retention behavior of the analyte germacrone was found, which was further investigated by the calculation of thermodynamic parameters. Meanwhile, enthalpy and entropy of the inclusion complexes and solute-stationary phase interactions were determined by linear van’t Hoff plots.     

Molecular dynamics study of the influence of solvents on the chiral discrimination of alanine enantiomers by β-cyclodextrin

The influence of solvents on the separation of alanine enantiomers using β-cyclodextrin as a chiral selector was studied by means of a molecular dynamics simulation at a constant temperature. The potential energy of the interaction is modelled by the AMBER force field, where different polar and non-polar solvents are represented by the dielectric constant ? and two configurations for the amino acid derived from its electric charge distribution: the AMBER data base or its zwitterion state. The l enantiomer has more positions inside the cavity of a β-cyclodextrin where it is more stable than the d-enantiomer in vacuo and solution, except for solvents such as hydrocarbons in which most positions of the d-alanine inside and outside the cavity are more stable. In all cases, the greatest differences are located near the cavity walls. Molecular dynamics simulations show that Ala is able to form inclusion complexes with β-cyclodextrin in vacuo and in solvents such as hydrocarbons, benzene, acetone, ethanol or water. The chiral discrimination of Ala by β-cyclodextrin is mainly due to the adaptation of the guest to the host in the presence of non-polar agents, whereas the nonbonded interaction is the driving force for zwitterions. The elution order depends on the type of organic modifiers while a reversal of the enantiomeric elution order can be observed in solvents with higher dielectric constants.     

Application of β-cyclodextrin in polymeric solid phase for separation and determination of lead in different environmental matrices

Immobilization of β-cyclodextrin on Dowex resin as an insoluble polymeric matrix by covalent bond presents a new solid-phase medium for preconcentration of Pb (II) at trace level in environmental samples prior to its flame atomic absorption spectrometric determination. The method is based on the sorption of lead after passing on modified Dowex sorbent in a column. The effect of several parameters such as pH, flow rate of sample, eluent kind and volume was investigated. The sorption capacity of the matrix has been found to be 0.4996?mg?g^?1 of adsorbent with the preconcentration factor of 250 for Pb (II). Nitric acid (3 M) as an eluent was sufficient to obtain quantitative recovery (>95%) for Pb (II). The optimum flow rate was 10?ml?min ^?1. The calibration curve was linear in the range of (3–250?ng?mL^?1) with a correlation coefficient of 0.9995. The limit of detection (LOD) based on three times the standard deviation of the blank was 1.37?ng?mL^?1. The relative standard deviation (RSD) for determination of 10?ng?mL^?1 and 100?ngmL^?1 of Pb (II) was 3.00 % and 0.58 % (n?=?10), respectively. The method was successfully applied to determination of lead in some environmental samples such as tap water, river water, soil and rice.     

A new approach to the synthesis of N-monosubstituted aniline and its derivatives via β-cyclodextrin host-guest complexes

A novel method for the synthesis of N-monosubstituted aniline and its derivatives β-cyclodextrin(CD)host-guest complexes has been presented.The mild reaction gives the title compounds with high selectivity in good yields of 90-98%.     

A new approach to the synthesis of N-monosubstituted aniline and its derivatives via β-cyclodextrin host-guest complexes

A novel method for the synthesis of N-monosubstituted aniline and its derivatives via β-cyclodextrin （CD） host-guest complexes has been presented. The mild reaction gives the title compounds with high selectivity in good yields of 90-98%.     

Direct chiral separation of abscisic acid by high-performance liquid chromatography with a phenyl column and a mobile phase containing γ-cyclodextrin

Abscisic acid (2-cis,4-trans-abscisic acid) is a plant hormone that has an asymmetric carbon atom. We tried to separate the enantiomers of native abscisic acid by HPLC using a phenyl column and a chiral mobile phase containing γ-cyclodextrin. The optimum mobile phase conditions were found to be 0.8% (w/v) γ-cyclodextrin, 4% (v/v) acetonitrile, and 20 mM phosphate buffer (pH 6.0). It was found that (R)-abscisic acid was earlier detected than (S)-abscisic acid. Since γ-cyclodextrin is hardly retained on a phenyl column, it was suggested that (R)-abscisic acid formed a more stable complex with γ-cyclodextrin than the (S)-abscisic acid. Abscisic acid in an acacia honey sample was successfully enantioseparated with the proposed method and only (S)-abscisic acid was detected. A biologically inactive 2-trans,4-trans-abscisic acid, which was prepared by irradiation of abscisic acid with a light-emitting diode lamp at 365 nm, was partially enantioseparated by the proposed method. Since the irradiation of (S)-abscisic acid-induced cis-to-trans isomerization to produce one 2-trans,4-trans-abscisic acid enantiomer, it is reasonable that racemization did not proceed during the cis-to-trans isomerization. (S)-Abscisic acid and probably (S)-2-trans,4-trans-abscisic acid were detected in a honey sample, where the peak area of (S)-abscisic acid was 7 times larger than that of (S)-2-trans,4-trans-abscisic acid.     

Enantiomeric separation of α-phenylethylamine and its analogs by mixed chiral and achiral stationary phase

A mixed stationary phase of modified β-cyclodextrin, 2,6-di-O-butyl-3-O-butyryl-β-cyclodextrin (phase A), and SE-54 (phase B) was used for enantiomeric separation of α-phenylethylami-ne, o,m,p-methyl and o,m,p-methoxy-substituted analogs. The composition of mixed phase was selected by comparison of each calculated amin(= (γm,i+1)/(γm,i))> the relative retention values of the most adjacent peaks, and γm,last, the relative retention values of the last eluting peak at each preselected ratio. Values of γm,i,α calculated by derived equations were in good agreement with the experimental results obtained with two specified mixed phases. All solutes investigated were almost baseline separated at a predicted composition of phase A and phase B in a single run within 18 minutes.     

Novel and efficient supramolecular synthesis of pyrroles in the presence of β-cyclodextrin in water

A simple and efficient synthesis of highly substituted pyrroles was achieved in water medium via multi-component strategy, using amine,DMAD/DEAD as well as phenacyl bromide catalyzed by β-CD.Utilizing this protocol various pyrrole derivatives were synthesized in good to excellent yields.     

Polyelectrolyte microcapsules containing molecules of sulfated β-cyclodextrin in the structure of nanosized shell

Alternate adsorption of the molecules of poly(allylamine hydrochloride) (PAA) and sulfated β-cyclodextrin (sulfo-β-CD) is studied by piezoelectric microweighing upon the formation of coatings of nanosized thicknesses by the polyionic assembly procedure. The thickness of planar coatings on the surface of single-crystalline silicon is determined by ellipsometry. The layer-by-layer character of the formation of planar nanosized coating is revealed and assumptions about the structure of the PAA and sulfo-β-CD bilayers are stated. A comparison of the spherical microparticles of polystyrene, as well as manganese and calcium carbonates, demonstrated that it is feasible to use microparticles of calcium carbonate as a template for producing microcapsules. Microcapsules with shells containing five (PAA/sulfo-β-CD) layers are prepared and studied by confocal fluorescent microscopy.     

A simple strategy for the synthesis of Zn-IL-SBA-15 by sol–gel and the application in desulfurization

Journal of Sol-Gel Science and Technology - SBA-15 functionalized with both zinc ions and ionic liquids was simply synthesized by sol–gel method. The characterization results of Fourier...     

Influence of solvent polarity on the separation of leucine enantiomers by β-cyclodextrin: a molecular mechanics and dynamics simulation

The interaction between leucine and β-cyclodextrin with different solvents was studied by molecular mechanics and dynamics simulations. In order to analyse the influence of the solvent polarity on the inclusion complex formation and separation process of leucine enantiomers by β-cyclodextrin, the organic modifiers were characterised by the same value of dielectric constant in the electrostatic contribution to the interaction energy, and a different molecular configuration of amino acids (neutral or zwitterion). The complexes formed in polar solvents were more stable than those in non-polar solvents with the same dielectric constant, because the electrostatic contribution is negative for the former and positive for the latter. The optimized structures obtained for leucine enantiomers and β-cyclodextrin in vacuo are non-inclusion complexes. The solvent polarity contributes to increasing the probability of the presence in an inner position for the guest, whereas the results for non-polar configurations were smaller and distributed in larger areas. The regions where the enantiomers spend more time in the simulation correspond to locations with greater chiral discrimination. d-Leu was the first eluted enantiomer in every case, except for a polar solvent with $\epsilon =26$.