Separation of ofloxacin enantiomers by capillary electrophoresis with fluorescence detection using deoxyribonucleic acid oligonucleotides as chiral selectors

This study used capillary electrophoresis with fluorescence detection- and a partial-filling mode-based method for chiral separation of ofloxacin. The deoxyribonucleic acid oligonucleotides with different base sequences were studied as potential chiral selectors including deoxyribonucleic acid tetrahedron, G-quadruplex, and G-riched double-strand deoxyribonucleic acid. Under the optimized conditions, all the deoxyribonucleic acid chiral selectors exhibited excellent chiral separation capabilities with a resolution higher than 1.5. The electrophoretic behavior of the ofloxacin enantiomer might result from the intermediate conjugate with different stabilities between chiral selectors and analytes by a combination of the hydrogen bond and spatial recognition structure. Moreover, satisfactory repeatability regarding run-to-run and interday repeatability was obtained, and all the relative standard deviation values of migration times and resolutions were below 4% (n = 6). Conclusively, both spatial structure and arrangement of the G bases potentiated the chiral separation capability of deoxyribonucleic acid for ofloxacin enantiomer. This work offered a stepping stone for enantioseparation using deoxyribonucleic acid as chiral selectors.     

毛细管电泳法手性拆分14种二肽

以咔唑-9-乙基氯甲酸酯(CEOC)作为柱前衍生试剂,采用毛细管电泳对14种二肽进行了手性拆分。以5种二肽为代表,考察了缓冲液种类、浓度、pH值、二元手性选择剂的组合配比等因素对二肽的拆分效果,优化了实验条件。在各自的优化条件下,14种二肽手性拆分的分离度均在3.63以上,最高分离度可达43.14(Gly-Ala)。     

A multichannel electrophoresis microchip platform for rapid chiral selector screening

This study presents a four-channel electrophoresis chip platform, featuring double-cross hydrostatic sample injection, for rapid chiral selector screening. This platform needs only five electrodes to drive microchip electrophoresis in four separate channels for screening four chiral selectors at a time. To demonstrate the performance of this screening platform, eight neutral CDs and their derivatives as chiral selectors were screened towards two FITC-labeled chiral compounds. The screening could be accomplished in less than 2 min. Dimethyl-beta-CD and hydroxypropyl-alpha-CD was demonstrated to be the appropriate selectors for FITC-norfenefrine and FITC-baclofen, respectively. The established platform is easy to operate and suitable for rapid screening process, which is expected to be a potential platform for high-throughput screening of chiral selectors.     

毛细管区带电泳法拆分手性药物萘普生和氟联苯丙酸

 70-72 -------------------------------------------------------------------------------- 以β-环糊精(CD)作为手性选择剂 ,用毛细管区带电泳法成功地拆分了两种弱酸性药物萘普生(naproxen)和氟联苯丙酸(flurb iprofen),并比较了4种环糊精［β-环糊精(β-CD)、二甲基-β-环糊精( DM-β-CD)、羟丙基-β-环糊精(HP-β-CD)和三甲基-β-环糊精( TM-β-CD)］对手性拆分的影响,同时测定了萘普生对映体在不同环糊精中的出峰次 序。通过实验,发现对于此类化合物拆分的最佳pH值为5左右,即接近于该类化合物的pK a值。该方法适用于酸性手性药物的拆分。     

Enantioseparation of four cis and trans diastereomers of 2',3'-didehydro-2',3'-dideoxythymidine analogs, by high-performance liquid chromatography and capillary electrophoresis

Compounds 1-4 are the four stereoisomers of a synthetic new potential antiviral agent (d4T analog) containing two chiral centers and a base (uracil). Both high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) techniques were used to separate and quantify enantiomers with high resolution. The determination of enantiomeric purity of the compounds was developed using both amylose chiral stationary phase by HPLC and anionic cyclodextrins (highly S-CD) as chiral selectors in CE. The HPLC method was found to be superior in sensitivity to the CE method.     

Peptide and peptidomimetic chiral selectors in liquid chromatography

The application of peptide and peptidomimetic chiral selectors in LC is reviewed in this article. In particular, methods for finding these types of selectors using combinatorial library approaches are discussed, as well as recent advances in the use of peptides and peptidomimetics as general chiral selectors for LC. In terms of the library approaches, batch screening and reciprocal screening are discussed. As for general chiral selectors, one example involves the application of chiral diamide phases. Another example shows the versatility of oligoproline chiral stationary phases, which exhibit resolution for a number of racemic analytes, comparable to other well-established chiral stationary phases.     

Enantiomeric Resolution of Benzoxazolinonic Aminoalcohols, Potential Adrenergic Ligands, by LC and CE

Benzoxazolinone amino alcohols are chiral derivatives that carry one asymmetric center. Both capillary electrophoresis and high-performance liquid chromatography (LC) techniques were used to separate enantiomers with high resolution and thus permitted the determination of enantiomeric excess. Highly sulfated and anionic cyclodextrins were used as chiral selectors under CE conditions. Amylose and cellulose chiral stationary phases were used for LC for the enantioseparation of five racemic compounds. Separations were carried out on a Chiralpak AS column with various polar organic modifiers. The HPLC method appeared more to be more sensitive and was subsequently validated in terms of limits of detection and quantification. LC detection was based on UV and evaporating light scattering.     

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.     

Enantioselective analysis of ofloxacin enantiomers by partial-filling capillary electrophoresis with bacteria as chiral selectors

The enantiomeric separation of ofloxacin enantiomers (OFLX) was achieved by using capillary electrophoresis partial-filled with Escherichia coli, Pseudomonas aeruginosa (Gram-negative), and Staphylococcus aureus (Gram-positive) as chiral selectors. Experimental parameters, including the concentration of background electrolyte, applied voltage, length of the filled bacteria plug, and pH of the buffer, were intensively investigated. Baseline separation of OFLX could be achieved within 7 min by using E. coli and P. aeruginosa as chiral selectors under the following conditions: electrophoretic buffer composed of 10 mM phosphate buffer at pH 7.4, applied voltage at 15 kV, and the bacteria (6.0 × 10(8) cells/mL) were injected into the capillary by gravity with injection height of 17.5 cm for 180 s (E. coli), 300 s (P. aeruginosa), and 300 s (S. aureus), respectively. E. coli and P. aeruginosa had better chiral selectivity for OFLX than S. aureus, which was in good agreement with OFLX having better antimicrobial activity on Gram-negative rather than Gram-positive bacteria. A novel method was developed for the enantioselective separation of enantiomers using bacteria as chiral selectors, which provides a new approach for antimicrobials enantioselective analysis, chiral pharmacodynamics, and chiral pharmacokinetics studies.     

Chiral capillary electrophoretic resolution of baclofen, gabaergic ligand, using highly sulfated cyclodextrins

Using cyclodextrin-capillary zone electrophoresis (CD-CZE), baseline separation of baclofen, a potent GABA(B) agonist; was achieved. A method for the enantioresolution of this gamma-aminobutyric acid (GABA) and determination of enantiomeric purity was developed using CDs (highly sulfated-CD or highly S-CD) as chiral selectors and capillaries dynamically coated with polyethylene oxide (PEO). Operational parameters, such as the nature and concentration of the chiral selectors, buffer concentration, organic modifiers, and applied voltage, were investigated. The use of charged CDs provides a driving force in the opposite direction of the positively charged baclofen in the running buffer and enantiomeric resolution by inclusion of compounds in the CD cavity. Highly S-beta-CD was found to be the most effective complexing agent, allowing good enantiomeric resolution. The complete resolution was obtained using 25 mM phosphate buffer, pH 2.5, containing 3% w/v highly S-beta-CD at 25 degrees C with aN applied field of 0.40 kV/cm. The apparent association constants of the inclusion complexes were calculated. This optimized method was validated in terms of repeatability and limits of detection (0.13 microg x mL(-1)) and quantification. The migration order was determined.     

组合手性萃取拆分克伦特罗外消旋体

以D-二苯甲酰酒石酸(D-DBTA)和D-二对甲苯甲酰酒石酸(D-DTTA)的组合作为手性选择剂,研究克伦特罗对映体在水相和有机相中的萃取分配行为,优化了手性萃取条件,考察了组合手性选择剂的不同摩尔浓度比、有机溶剂、水相pH值和亲脂性阴离子BPh4-对手性萃取性能的影响,并测定了手性萃取拆分过程中的热力学函数.在优化的手性萃取条件下,有机相中的对映体过量值(e.e.%)可大于10%,而所使用的选择剂量相对大为降低.热力学数据分析表明,该手性萃取过程为焓控过程.     

Properties of L-phenylalanine tetraamides as chiral selectors for D,L-amino acids by capillary gas chromatography

Summary A wide series of L-phenylalanine tetraamide selectors (Phe-n-O-TA) have been synthesized and used as stationary phases for chiral resolution of D,L-amino acids by capillary gas chromatography. The influence of length and polarity of the oxaalkanoyl bridge spacing the diamide chains of the selectors and the effects of steric hindrance on separating power were investigated. The characteristics of the chiral columns and the separation factors of D,L-n-butyl-N-trifluoroacetyl amino esters are reported.     

Cyclodextrins as chiral selectors in capillary electrophoresis: a comparative study for the enantiomeric separation of some beta-agonists.

A comparative study for the enantiomeric separation of terbutaline, clenbuterol, salbutamol and dobutamine was performed by capillary electrophoresis using cyclodextrins and their derivatives as chiral selectors. Several parameters such as buffer composition and temperature were studied. Simple, fast and reliable enantioseparations were achieved for all drugs studied, especially when the isomerically pure sulfated beta-cyclodextrin derivatives were used as chiral selectors.     

Evaluation of chiral purity for a substituted imidazole p38 MAP kinase inhibitor and its intermediates using a single chiral capillary electrophoresis method

The chiral separation of a substituted imidazole p38 MAP kinase inhibitor and its intermediates was investigated using capillary electrophoresis (CE) with various sulfated cyclodextrins. After initial screens, a single CE chiral method with a randomly sulfated beta-CD was selected for the evaluation of chiral purity for all three compounds. Operational parameters, such as the concentration of the chiral selectors, background electrolyte (or mobile phase) pH, organic modifiers, and temperature were varied in order to achieve an optimized method. The optimal method was validated in terms of linearity, sensitivity, precision, ruggedness, and specificity.     

Recent advances in peptide chiral selectors for electrophoresis and liquid chromatography

The application of peptides in chiral separations using techniques such as capillary electrophoresis (CE), electrokinetic capillary chromatography (EKC) and liquid chromatography is the focus of this review. Methods for finding peptide selectors using combinatorial library approaches are discussed, as well as recent advances in the use of peptides as general chiral selectors for electrophoresis and liquid chromatography. One example shows the effectiveness of polymeric dipeptide surfactants as general chiral selectors for electrophoresis. Another example shows the versatility of oligoproline chiral stationary phases, exhibiting resolution for a number of racemic analytes comparable to other well-established chiral stationary phases.     

双手性选择单元手性固定相的研究进展

手性固定相（chiral stationary phase,CSP）作为手性色谱分离的核心技术,在手性化合物的识别和分离中得到广泛应用。以双手性选择单元结合作为CSP是近些年的研究热点,研究表明,两种手性选择单元相结合的CSP可增加手性识别位点,显著提高分离效果。本文介绍了近几年双手性选择单元手性固定相在手性分离中的研究进展,并对其发展前景进行了展望。     

Comparison of enantioseparations using Cu(II) complexes with L-amino acid amides as chiral selectors or chiral stationary phases by capillary electrophoresis,capillary electrochromatography and micro liquid chromatography

In this paper we report that Cu(II) complexes with L-amino acid amides were used as chiral selectors for enantioseparation by capillary electrophoresis, capillary electrochromatography (CEC) and micro liquid chromatography using chemically modified monolithic columns. The enantioselectivity, enantiomer migration order, and the performance have been compared when different chiral selectors were used in these modes. L-Enantiomers showed longer retention times than D-forms in both CEC and LC modes. However, it has interestingly been observed that the migration order of Dns-DL-Ser showed an exception in CEC using L-prolinamide-modified column that Dns-L-Ser was eluted as the first peak. On the basis of proposed structures of complexes in the chiral recognition, differences in migration orders and recognition mechanism were discussed.     

Bile Salts in Chiral Micellar Electrokinetic Chromatography: 2000–2020

Bile salts are naturally occurring chiral surfactants that are able to solubilize hydrophobic compounds. Because of this ability, bile salts were exploited as chiral selectors added to the background solution (BGS) in the chiral micellar electrokinetic chromatography (MEKC) of various small molecules. In this review, we aimed to examine the developments in research on chiral MEKC using bile salts as chiral selectors over the past 20 years. The review begins with a discussion of the aggregation of bile salts in chiral recognition and separation, followed by the use of single bile salts and bile salts with other chiral selectors (i.e., cyclodextrins, proteins and single-stranded DNA aptamers). Advanced techniques such as partial-filling MEKC, stacking and single-drop microextraction were considered. Potential applications to real samples, including enantiomeric impurity analysis, were also discussed.     

基于环糊精手性选择剂的几种手性药物对映体的毛细管电泳拆分

以环糊精(-αCD、-βCD和-γCD)为手性选择剂,采用毛细管电泳对扑尔敏、异丙嗪和二氧异丙嗪对映体进行了分离,考察了手性选择剂的浓度、缓冲液pH值及有机添加剂对手性分离的影响,并就拆分机理进行了初步探讨.     

Enantiomer separation of chiral pharmaceuticals by capillary electrochromatography

Enantiomer separation of chiral pharmaceuticals by capillary electrochromatography (CEC) is achieved with open-tubular capillaries (o-CEC), with packed capillaries (p-CEC) or with monolithic capillaries. In o-CEC, capillaries are coated with a thin film containing cyclodextrin derivatives, cellulose, proteins, poly-terguride or molecularly imprinted polymers as chiral selectors. In p-CEC, typical chiral HPLC stationary phases such as silica-bonded cyclodextrin or cellulose derivatives, proteins, glycoproteins, macrocyclic antibiotics, quinine-derived and 'Pirkle' selectors, polyacrylamides and molecularly imprinted polymers are used as chiral selectors. Chiral monolithic stationary phases prepared by in situ polymerization into the capillary were also developed for electrochromatographic enantiomer separation.