毛细管区带电泳法拆分手性药物环扁桃酯

近年来,随着不同种类的手性添加剂[1]在毛细管电泳(CZE)中的使用,毛细管电泳越来越显示出其强有力的手性拆分性能。具有特殊笼状结构并含有多个手性中心的环糊精及其衍生物是毛细电泳手性分离研究中最常采用的手性添加添[2-4]。本文合成了环糊精衍生物单3 O 苯基胺甲酰基 β CD[2]并以之作为手性选择剂分离了β CD及手性药物环扁桃酯。1　实验部分932 3 HVPS高压电源(山东省化工研究院),DD 2000型可调波长紫外检测器(中国科学院大连化学物理研究所),XWT型记录仪(上海大华仪表厂),pHS 25型酸度计(上海雷磁仪器厂),石英毛细管45cm…     

Enantiomeric separation by capillary electrophoresis with an electroosmotic flow-controlled capillary

Perfect control of electroosmotic flow (EOF) was achieved by dovetailing successive multiple ionic-polymer layer (SMIL) coated capillaries. The direction and magnitude of the EOF was perfectly controllable over the pH range 2-13. Zone diffusion was not observed, even if the inner wall of the dovetailed capillary was discontinuous, or if the sample zone passed through the connected part of the capillary because the RSDs of migration time, theoretical plates, symmetry factor and S/N of the marker were almost the same when seamless capillary and dovetailed capillary were compared. The dovetailed capillary was applied to cyclodextrin modified capillary zone electrophoresis. The control of the EOF enabled us to control both the resolution and the migration order of the enantiomers. The migration time was also controllable and, therefore, the best condition between separation and migration time could be determined by controlling the EOF. Partial filling affinity electrokinetic chromatography with a protein used as a chiral selector was also studied. The migration of the pseudostationary phase was controllable by EOF, and detection of the solute at 214 nm was possible. Therefore, the EOF-controlled dovetailed capillary has great potential to expand the application of the separation technique.     

Enantiomeric separation of racemic clenbuterol by capillary zone electrophoresis

A method for capillary electrophoretic enantiomeric separation of a racemic clenbuterol has been established with hydroxypropyl-β-cyclodextrin as the chiral selector. General equations and data analysis are presented to relate mobility to the equilibrium constants in simple binding equilibria and used to determine binding constants and thermodynamic parameters for host-guest complexation of clenbuterol enantiomers with hydroxypropyl-β-cyclodextrin as a selector. The effects of β-cyclodextrin type and concentration, buffer type, concentration and pH, as well as separation voltage and capillary temperature were investigated in detail. A maximal resolution of 6.78 was obtained. The binding constants of the host-guest complex of clenbuterol enantiomers with hydroxypropyl-β-cyclodextrin, K _R-CD and K _S-CD are 22.50 and 43.09 l mol^-1, respectively.     

Enantiomeric separation of citalopram and its metabolites by capillary electrophoresis

A simple and fast capillary electrophoretic method has been developed for the enantioselective separation of citalopram and its main metabolites, namely N-desmethylcitalopram and N,N-didesmethylcitalopram, using beta-cyclodextrin (beta-CD) sulfate as the chiral selector. For method optimisation several parameters were investigated, such as CD and buffer concentration, buffer pH, and capillary temperature. Baseline enantioseparation of the racemic compounds was achieved in less than 6 min using a fused-silica capillary, filled with a background electrolyte consisting of a 35 mM phosphate buffer at pH 2.5 supplemented with 1% w/v beta-CD sulfate and 0.05% w/v beta-CD at 25 degrees C and applying a voltage of -20 kV. A fast separation method for citalopram was also optimized and applied to the analysis of pharmaceutical formulations. Racemic citalopram was resolved in its enantiomers in less than 1.5 min using short-end injection (8.5 cm, effective length) running the experiments in a background electrolyte composed of a 25 mM citrate buffer at pH 5.5 and 0.04% w/v beta-CD sulfate at a temperature of 10 degrees C.     

毛细管区带电泳对手性药物盐酸美西律和盐酸异博定的对映体分离

应用环糊精-毛细管区带电泳体系对手性药物盐酸美西律和盐酸异博定的对映体分离进行了研究。结果表明, 在所研究的手性选择剂α-环糊精, β-环糊精, 二甲基-β-环糊精, 羟丙基β-环糊精和γ-环糊精中, 羟丙基β-环糊精对所研究的手性药物分离效果较好。对盐酸美西律和盐酸异博定的最佳羟丙基-β-环糊精浓度分别为30mmol/L和9mmol/L, 最佳缓冲溶液浓度为100mmol/L Tris-H3PO4(pH2.3)。向缓冲溶液中加入0.05%羟丙基纤维素(HPLC)可改善分离。盐酸美西律获得了接近基线的手性分离, 而盐酸异博定亦获得了较好的分离。     

Enantiomeric separation of neutral hydrophobic dihydrofuroflavones by cyclodextrin-modified micellar capillary electrophoresis

The enantiomeric separations of several very hydrophobic dihydrofuroflavones were performed and optimized using cyclodextrin-modified micellar capillary electrophoresis. Overall, the greatest enantiomeric peak-to-peak separations for the greatest number of flavones were obtained with hydroxypropyl-gamma-cyclodextrin. The effects of cyclodextrin and sodium dodecyl sulfate concentration and pH were examined in order to optimize the separation conditions. The ratio of surfactant-to-cyclodextrin concentration affected the chiral discrimination of the system significantly, with increases in the derivatized cyclodextrin concentration generally enhancing resolution. Higher efficiencies were obtained with lower concentrations of surfactant and cyclodextrin, although enantioseparation optimization often required higher concentrations to be used. A highly acidic pH was necessary to effectively suppress the electroosmotic flow when operating in the reversed polarity mode. Experiments utilizing the normal polarity mode and higher pH produced no separations.     

Enantiomeric separation of acidic compounds using single-isomer amino cyclodextrin derivatives in nonaqueous capillary electrophoresis

The enantiomeric separation of a series of acidic pharmaceuticals (mostly nonsteroidal anti-inflammatory drugs) has been investigated in NACE systems using single-isomer amino beta-CD derivatives. The first part of this study consisted of the selection of the basic experimental conditions to separate efficiently the enantiomers of acidic drugs. Several parameters, such as the nature of the ionic BGE components, were studied and a methanolic solution of ammonium acetate containing the cationic CD was selected as BGE. A D-optimal design with 20 experimental points was then applied and the nature and concentration of the CD were found to have a significant effect on the enantiomeric resolution for all studied compounds. Resolution (R(s)) values were always higher with 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-CD (PA-beta-CD) compared to those obtained with 6-monodeoxy-6-mono(2-hydroxy)propylamino-beta-CD (IPA-beta-CD). However, the latter led to shorter migration times. Generic NACE conditions were then selected by means of the multivariate approach in order to obtain the highest R(s) values in a minimum amount of time. Finally, dependence of separation selectivity, resolution, as well as mobility difference on chiral selector concentration was discussed and binding constants with PA-beta-CD were estimated for the two enantiomers of one of the model compounds, suprofen in these NACE systems.     

Enantiomeric separations by nonaqueous capillary electrophoresis

This paper reviews the recent advances in enantioseparations by nonaqueous capillary electrophoresis (NACE) and the effect of organic solvents on mobility of enantiomers, separation selectivity and resolution. In general, the enantioseparation systems in NACE are similar to those of aqueous capillary electrophoresis (CE) except pure organic solvents are used. The influence of important parameters such as concentration and type of chiral selectors, apparent pH, ionic strength, temperature, and control of electroosmotic flow is discussed. In addition, the reported applications of NACE separations of racemates are presented.     

Enantiomeric separation of furan derivatives and fused polycycles by cyclodextrin-modified micellar capillary electrophoresis

The enantiomeric separations of highly hydrophobic furan derivatives and polycycles were performed and optimized using CD-modified micellar CE. The most effective chiral selector for the enantiomeric separation of these analytes was hydroxypropyl-gamma-CD. The effects of CD and SDS concentration and organic modifier were examined in order to optimize the separation conditions. The ratio of CD to surfactant concentration affected the enantiomeric separation significantly, with increases in the derivatized CD concentration generally enhancing resolution. Addition of an organic solvent modifier to the run buffer served to increase the analytes' solubility and enhance the separation efficiency. A highly acidic pH was necessary to effectively suppress the EOF when operating in the reverse polarity mode.     

Enantiomeric separation of glycyl dipeptides by capillary electrophoresis with cyclodextrins as chiral selectors

Uncharged cyclodextrins were tested as chiral selectors for the enantiomeric separation of 13 glycyl dipeptides with capillary electrophoresis. Initial experiments were performed on 10 mmol/L of a cyclodextrin in 0.1 mol/L phosphoric acid -0.088 mol/L triethanolamine. Some of the resolved dipeptides were nonaromatic, which is noteworthy since, to our knowledge, no examples of the separation of small, nonaromatic molecules have been published. Mobility difference plots for Gly-DL-Leu and Gly-DL-Phe with heptakis(2,6-di-O-methyl)-beta-cyclodextrin showed relatively flat profiles in a large concentration range, which is an advantage for the development of robust quantitative analytical methods. The use of a background electrolyte (BGE) solution with pH 3.0 gave irreproducible results for two of the dipeptides, the acidic Gly-DL-Asp and Gly-DL-Glu; this pH is not advisable for the development of robust methods for these two peptides. The need for purer chiral selectors was demonstrated by comparing different batches of heptakis(2,6-di-Omethyl)-beta-cyclodextrin from the same supplier. A BGE consisting of malonic acid and triethanolamine was introduced to give better buffer capacity than the original BGE at pH 3.0.     

Enantiomeric separation by capillary electrophoresis using a crown ether as chiral selector.

This paper reviews chiral separations of primary amines by capillary electrophoresis and crown ether as chiral selector. Two possible mechanisms of chiral recognition by host-guest complexation are discussed: (i) The substituents of the crown ether act as barriers for the guest compounds, and (ii) lateral electrostatic interactions between host and guest occur. Experimental conditions affecting the separation are discussed in detail. A literature overview of practical applications is presented as well. More than 80 different primary amines were analyzed, whereupon the majority could be resolved using a screening method. It is shown that a synergistic effect on the resolution of chiral amines is observed when the chiral crown ether and cyclodextrins are simultaneously used in the same buffer system. This approach opens interesting perspectives for further method optimization.     

Enantiomeric and isomeric separation of herbicides using cyclodextrin-modified capillary zone electrophoresis

Cyclodextrin-modified capillary zone electrophoresis (CD-CZE) was applied successfully to the enantiomeric and isomeric separation of three herbicides (imazaquin, diclofop and imazamethabenz). Commercially available cyclodextrins were evaluated for separation of the enantiomers and isomers of the three herbicides having varied molecular structures. The enantiomers of imazaquin and diclofop, and the isomers of imazamethabenz could be resolved with a resolution of ≥1.5. The resolution was found to depend on pH of the run buffer, cyclodextrin type and cyclodextrin concentration. By employing mixed cyclodextrins in the running buffer, the three herbicides were simultaneously separated in a single run. In addition, rapid (less than 3 min) enantiomeric separation is demonstrated using imazaquin as a model herbicide. The reported capillary electrophoresis (CE) methods are simple, rapid, efficient and reproducible and our results demonstrate that CE provides a powerful analytical tool for enantiomeric and isomeric separation of herbicides.     

Enantiomeric separation of chiral peptide nucleic acid monomers by capillary electrophoresis with charged cyclodextrins

Direct chiral separation of chiral peptide nucleic acid (PNA) monomers has been achieved for the first time by capillary electrophoresis (CE) with charged cyclodextrins as chiral selectors added to the electrophoretic buffer. Selectively modified 6-deoxy-6-N-histamino-beta-cyclodextrin and sulfobutyl ether-beta-CD were successfully used as chiral selectors for the enantiomeric separation of chiral monomers based on different aminoethylamino acids bearing thymine or adenine as nucleobases. Chiral separations were obtained at low selector concentrations (1-3 mM) with good enantioselectivity and resolution factors. Separations were optimized as a function of pH in order to exploit the effect of the electrostatic interactions between the oppositely charged selector and selectand. The method has been applied to the analysis of the enantiomeric excess of chiral monomers used for the solid phase synthesis of chiral PNA oligomers. CE chiral analysis showed that a very high enantiomeric purity was generally achieved in the synthesis of all monomers, except for histidine and aspartic acid based monomers in which ca. 10% of the "wrong" enantiomer was always present.     

Enantiomeric separation of some common controlled stimulants by capillary electrophoresis with contactless conductivity detection

CE methods with capacitively coupled contactless conductivity detection (C⁴D) were developed for the enantiomeric separation of the following stimulants: amphetamine (AP), methamphetamine (MA), ephedrine (EP), pseudoephedrine (PE), norephedrine (NE) and norpseudoephedrine (NPE). Acetic acid (pH 2.5 and 2.8) was found to be the optimal background electrolyte for the CE‐C⁴D system. The chiral selectors, carboxymethyl‐β‐cyclodextrin (CMBCD), heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DMBCD) and chiral crown ether (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid (18C6H₄), were investigated for their enantioseparation properties in the BGE. The use of either a single or a combination of two chiral selectors was chosen to obtain optimal condition of enantiomeric selectivity. Enantiomeric separation of AP and MA was achieved using the single chiral selector CMBCD and (hydroxypropyl)methyl cellulose (HPMC) as the modifier. A combination of the two chiral selectors, CMBCD and DMBCD and HPMC as the modifier, was required for enantiomeric separation of EP and PE. In addition, a combination of DMBCD and 18C6H₄ was successfully applied for the enantiomeric separation of NE and NPE. The detection limits of the enantiomers were found to be in the range of 2.3–5.7 μmol/L. Good precisions of migration time and peak area were obtained. The developed CE‐C⁴D method was successfully applied to urine samples of athletes for the identification of enantiomers of the detected stimulants.     

Enantiomeric separation of dansylamino acids by capillary zone electrophoresis based on complexation with cyclodextrins

Summary The enantiomeric separation ability of unmodified and methylated cyclodextrins (CDs) during capillary zone electrophoresis (CZE) was investigated using twelve dansylamino acids. Unmodified - and -CDs exhibited high enantioselectivities. -CD could scarcely separate the enantiomers before and after dimethylation, but obtained enantioselectivity after trimethylation. On the other hand, dimethylation of -CD removed much of its high enantioselectivity. Moreover, the chemical modifications produced a reverse in the migration order of the enantiomers. The inclusion of dansyl-DL-phenylalanine with CDs was evaluated using 600 MHz ¹H NMR spectroscopy.     

Nonaqueous media for separation of nonionic organic compounds by capillary electrophoresis

For the separation of neutral compounds by micellar electrokinetic chromatography, separations are usually carried out in predominantly aqueous solution in order to preserve the charged micelle necessary for the separation. We now show that polycyclic aromatic hydrocarbon (PAH) compounds can be separated efficiently by capillary electrophoresis in pure methanol or in aqueous-organic mixtures containing a high percentage of methanol. Sodium tetradecyl sulfate was the preferred surfactant. The effects of pH, solvent composition, surfactant structure, and surfactant concentration on the separations were studied. Reproducible migration times and linear calibration plots were obtained.     

Enantiomeric separation of alanyl and leucyl dipeptides by capillary electrophoresis with cyclodextrins as chiral selectors

Eight neutral cyclodextrins were tested for the enantiomeric separation of alanyl and leucyl dipeptides by capillary electrophoresis at pH 3, and seven out of the eight cyclodextrins proved suitable for the separation of one or more of the dipeptide enantiomer pairs. The best results were obtained with heptakis(2,6-di-O-methyl)-beta-cyclodextrin. The dipeptides that were separated were mainly the aromatic and the more lipophilic aliphatic dipeptides. Mobility difference plots at pH 3.0 with malonic acid-triethanolamine as background electrolyte showed that the aromatic dipeptides had higher affinities for the cyclodextrin than the nonpolar, aliphatic dipeptides. The results suggested that, under the conditions applied, the C-terminal amino acid rather than the N-terminal one is involved in the chiral discrimination.     

Enantiomeric separation by cyclodextrin modified capillary zone electrophoresis (CD-CZE) of quaternary tetrahydroprotoberberine alkaloids

A cyclodextrin modified capillary zone electrophoresis (CD-CZE) for the enantiomeric separation of tetrahydroprotoberberine N-metho salts was established. The resolution was optimized by changing the concentration of the electrolyte solution, hydroxypropyl-beta-CD (0.02 M, 0.07 M, or 0.14 M) or dimethyl-beta-CD (0.05 M or 0.15 M) in phosphate buffer (pH 2.5 or 3) containing 10% acetonitrile with an applied voltage of 20 kV. This method was applied toward the enantioselective bio-conversion of quaternary tetrahydroprotoberberine N-metho salts in cultured cells of Corydalis species.