Chiral resolution of basic drugs by capillary electrophoresis with new glycosaminoglycans

New glycosaminoglycans, fucose-containing glycosaminoglycan (FGAG) and depolymerized holothurian glycosaminoglycan (DHG), were investigated as chiral additives for the separation of drug enantiomers by capillary electrophoresis. The average molecular masses of FGAG and DHG were estimated to be about 59,000 and 14,000, respectively. A variety of basic drug enantiomers were resolved using 10 mM phosphate buffer, pH 5.0, containing 3% FGAG or DHG. Since chiral recognition properties of FGAG and DHG are different, some drug enantiomers were only separated by using FGAG or DHG. With regard to comparison of chiral recognition abilities of FGAG and DHG with other chiral selectors, tolperisone and eperisone enantiomers were not separated with alpha- or beta-cyclodextrin, or heparin as the chiral additives, but were separated with FGAG and DHG. The results obtained reveal that FGAG and DHG are useful as the chiral selectors for separations of drug enantiomers by CE, and that they could be complementarily used with other chiral additives.     

Rapid separation of basic drugs by nonaqueous capillary electrophoresis

Summary Nonaqueous capillary electrophoresis (NACE) has been used to achieve rapid separations of basic drugs. A high electric field was obtained by using short capillaries. Baseline separations of basic drugs, including amphetamines, tropane alkaloids and local anesthetics, were achieved in 1 min by selection of the appropriate organic solvent and electrolyte composition. Thus, high-throughput analyses can be performed. Peak efficiency up to 9154 theoretical plates s⁻¹ was achieved in a separation performed at 923V cm⁻¹. No discernible loss in resolution was observed when a conventional capillary (64.5cm) was replaced by a short (32.5 cm) capillary.     

Chiral separation by capillary electrophoresis with oligosaccharides.

Maltodextrins, i.e., mixtures of linear alpha-(1-4)-linked D-glucose polymers, were found to be effective as chiral electrolyte modifiers to perform direct, rapid separations by capillary electrophoresis of racemic mixtures of 2-arylpropionic acid non-steroidal anti-inflammatory compounds and coumarinic anticoagulant drugs, and also diastereomeric cephalosporin antibiotics. Enantioselectivity seemed to be dependent on an as yet unidentified combination of variables.     

Chiral separation of cetirizine by capillary electrophoresis

Chiral separation of cetirizine, a second-generation H(1)-antagonist, was studied by CD-mediated CE. Several parameters, including pH, CD type, buffer concentration, type of co-ion, applied voltage and temperature, were investigated. The best conditions for chiral separation were obtained using a 75 mM triethanolamine-phosphate buffer (pH 2.5) containing 0.4 mg/mL heptakis(2,3-diacetyl-6-sulfato)-beta-CD and 10% ACN. Online UV detection was performed at 214 nm, a voltage of 20 kV was applied and the capillary was temperature controlled at 25 degrees C by liquid cooling. Hydrodynamic injection was performed for 1 s. The method was validated for the quantification of levocetirizine in tablets and for enantiomeric purity testing of the drug substance. Selectivity, linearity, LOD and LOQ, precision and accuracy were evaluated for both methods. The amount of levocetirizine dihydrochloride in the commercially available tablets was quantified and was found to be within the specification limits of the claimed amount (5 mg). The amount of distomer in levocetirizine drug substance was found to be 0.87 +/- 0.09% w/w, which is in agreement with the certificate of analysis supplied by the company.     

Chiral separation of cathinone derivatives used as recreational drugs by cyclodextrin-modified capillary electrophoresis

In recent years, cathinone derivatives have entered the global drug market and caused serious social problems in many European countries. Modification of the basic structure of cathinone leads to a multitude of derivatives, including the most popular representative mephedrone. All those substances contain a stereogenic center and therefore two isoforms exist. As it is the case with many chiral active pharmaceutical ingredients, even the pharmacological effect of the enantiomers of those psychoactive compounds may differ. During this research, an easy-to-prepare chiral capillary zone electrophoresis method for the enantioseparation of a set of 19 cathinone derivatives was developed. Testing different types of cyclodextrin (CD), including native-β-CD, carboxymethyl-β-CD, 2-hydroxypropyl-β-CD, sulfated-β-CD, and native γ-CD, best results were obtained with the negatively charged sulfated-β-CD. The effect of the CD concentration, the temperature, and the addition of ACN to the BGE on the enantioseparation is shown by three model compounds. Under optimal conditions, using 20 mg/mL sulfated-β-CD in 50 mM ammonium acetate buffer pH?= 4.5 containing 10% v/v ACN at a cassette temperature of 40°C and with an applied voltage of 20 kV, all derivatives except methedrone were resolved in their enantiomers within 20 min.     

Chiral separation of local anaesthetics with capillary electrophoresis

Summary A chiral capillary electrophoresis system for the highresolution separation of the enantiomers of the local anaesthetics mepivacaine, ropivacaine, bupivacaine and prilocaine is described. Triethanolamine was added to the background electrolyte to obtain a negative electroosmotic flow and hence higher resolutions. The interactions of the local anaesthetics and their chemical analogues with the chiral selector, dimethyl--cyclodextrin, were studied. From a model describing chiral capillary electrophoresis, the association equilibrium constants were determined by curve-fitting. The separation of mepivacaine, ropivacaine and bupivacaine was due to the different mobilities of the free analytes in solution, whereas the separation of a pair of enantiomers of a single analyte was due to differences between the association equilibrium constantsK ₁ andK ₂. Branching of the alkyl chain, which was situated close to the cavity in the inclusion complex, had strong effects on the chiral separation of the enantiomers.     

用羧甲基聚合环糊精作手性剂的毛细管电泳法分离3种碱性药物

 采用 5种环糊精衍生物对碱性药物硫喷妥钠、盐酸氟桂利嗪、山梗菜碱进行了毛细管区带电泳的手性拆分。结果表明 ,采用含 2 % (质量分数 ,其余相同 )聚合 β 环糊精 (P β CD)或 0 5%羧甲基聚合 β 环糊精 (CM P β CD) 30mmol/L的Tris H3PO4缓冲液可使这 3种药物达到基线分离 ;使用CM P β CD时 ,分离度高达 4～35。     

Chiral separation of amino acids and peptides by capillary electrophoresis

Chiral separation of amino acids and peptides by capillary electrophoresis (CE) is reviewed regarding the separation principles of different approaches, advantages and limitations, chiral recognition mechanisms and applications. The direct approach details various chiral selectors with an emphasis on cyclodextrins and their derivatives, antibiotics and chiral surfactants as the chiral selectors. The indirect approach deals with various chiral reagents applied for diastereomer formation and types of separation media such as micelles and polymeric pseudo-stationary phases. Many derivatization reagents used for high sensitivity detection of amino acids and peptides are also discussed and their characteristics are summarized in tables. A large number of relevant examples is presented illustrating the current status of enantiomeric and diastereomeric separation of amino acids and peptides. Strategies to enhance the selectivity and optimize separation parameters by the application of experimental designs are described. The reversal of enantiomeric elution order and the effects of organic modifiers on the selectivity are illustrated in both direct and indirect methods. Some applications of chiral amino acid and peptide analysis, in particular, regarding the determination of trace enantiomeric impurities, are given. This review selects more than 200 articles published between 1988 and 1999.     

毛细管区带电泳法拆分匹伐他汀钙对映体

建立了匹伐他汀钙对映体的毛细管区带电泳(CZE)拆分方法。分别考察了电泳电压,缓冲溶液种类、浓度及pH值,环糊精种类及浓度,添加剂种类及浓度等参数对实验结果的影响,从而确定了匹伐他汀钙对映体的最佳拆分条件: 电泳电压为18 kV;运行缓冲溶液为80 mmol/L的Tris-HCl缓冲体系,pH值为3.20,其中含有50 mmol/L HP-β-CD(羟丙基-β-环糊精)和5 mmol/L SDS(十二烷基磺酸钠);采用重力进样,进样高度17 cm,进样时间为2 s。在优化的实验条件下,匹伐他汀钙对映体得到了较好的分离,分离度可达2.17。实验结果表明该方法可用于匹伐他汀钙对映体的分离,具有快速、便捷、准确性好等优点。     

Chiral separation of highly negatively charged enantiomers by capillary electrophoresis

The separation of two highly negatively charged enantiomeric organic disulfates containing two chiral centers was investigated by capillary electrophoresis using cyclodextrin based chiral selectors added to the run buffer. The optimum separation for the enantiomers was achieved in less than 3 min at 25 degrees C with a run buffer of 10 mM glycine pH 2.4 and 5 mM QA-beta-CD, which is a positively charged quaternary ammonium beta-cyclodextrin derivative. The method resulted in baseline resolution, excellent linearity, and highly reproducible migration times allowing facile evaluation of the enantiomeric purity of the individual isomers. Detection limits for the enantiomeric pair were determined to be 0.3 ng/microl (S/N = 3). The nature of the selector-enantiomer interaction and a quantitative measurement of the apparent stability constants that governed chiral discrimination of the enantiomers with QA-beta-CD were also investigated by UV-Vis spectroscopy and electrospray ionization mass spectrometry.     

Chiral separation of quinolones by liquid chromatography and capillary electrophoresis

The quinolones are derivatives of oxoquinolines and mostly known for their antibacterial and antiviral activities. Many quinolones are chiral compounds having asymmetric centers and important due to their enantioselective biological activities. In order to study the biological activities of quinolone enantiomers, to control the manufacturing of homochiral drugs and to prepare necessary quantities of pure enantiomers for preclinical or clinical trials, respective chiral separation methods are urgently needed. In this context, the present review discusses chromatographic and electrophoretic methods for the enantioseparation of chiral quinolones and provides some useful information on their physical and pharmaceutical properties. The drawbacks of currently used techniques are revealed and ways to overcome them are outlined. Moreover, recommendations for an optimal choice of a separation protocol are given.     

Chiral separation of halogenated amino acids by ligand-exchange capillary electrophoresis

The chiral separation of halogenated amino acids by ligand-exchange CE is described. Halogenated amino acids attracted increasing interest in recent years because of their physiological activities. Different chiral selectors, as there are L-4-hydroxyproline, L-histidine, and N-alkyl derivatives of L-4-hydroxyproline in form of their copper(II) complexes, are compared for their chiral recognition ability for halogenated amino acids. The influence of various parameters, such as selector concentration, pH, organic modifier, and field strength, on the resolution was investigated. All halogenated amino acids investigated were baseline-separated under optimized conditions.     

Chiral separation of sympathomimetics by ligand exchange capillary electrophoresis.

A rapid and simple approach to the chiral separation of sympathomimetic drugs with amino alcohol structure by ligand exchange capillary electrophoresis is described. An N-(2-hydroxyoctyl)-L-4-hydroxyproline/copper(II) complex is used as chiral selector. Thirteen sympathomimetics were resolved, nine with baseline resolution. The influence of pH and composition of the electrolyte on resolution was investigated. The optimal pH for complexation of these amino alcohols was found to be 12.     

Chiral separation of the plant lignan matairesinol by capillary electrophoresis

Lignans are dimeric phenylpropanoid compounds in plants that enjoy increasing medicinal interest because of their phytoestrogen activity. Lignans are chiral compounds and for most natural occurring lignans, chirality is not known. Separation of racemic matairesinol by CE in a non-coated silica capillary with carboxymethyl-beta-cyclodextrin as chiral selector in phosphate buffer was successful. Electrolyte and selector concentrations and pH were systematically optimized in order to obtain baseline separation and short analysis times. Matairesinol from safflower fruit was determined as (-)-enantiomer. Quantitation results for matairesinol with the optimized method after calibration with authentic lignan were very similar to those by HPLC. The limit of detection is 2 microg/mL sample by DAD detection.     

Chiral separation of amino acids by capillary electrophoresis with octyl-beta-thioglucopyranoside as chiral selector

In the present work, we propose the use of direct coupling of a headspace sampler to a mass spectrometer for the detection of adulterants in olive oil. Samples of olive oils were mixed with different proportions of sunflower oil and olive-pomace oil, respectively, and patterns of the volatile compounds in the original and mixed samples were generated. Application of the linear discriminant analysis technique to the data from the signals was sufficient to differentiate the adulterated from the non-adulterated oils and to discriminate the type of adulteration. The results obtained revealed 100% success in classification and close to 100% in prediction. The main advantages of the proposed methodology are the speed of analysis (since no prior sample preparation steps are required), low cost, and the simplicity of the measuring process.     

Chiral separation of labetalol stereoisomers in human plasma by capillary electrophoresis

A newly derivatized cyclodextrin [octakis-(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin] was investigated as a chiral selector in capillary zone electrophoresis in a study of the chiral separation of labetalol stereoisomers. Heptakis(2,3-diacetyl-6-sulfato)-beta-cyclodextrin (HDAS-beta-CD) and octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin (ODAS-gamma-CD) were shown to be effective in separating labetalol stereoisomers. Optimal separating conditions of the four stereoisomers of labetalol were achieved with 10 mM HDAS-beta-CD and 10 mM ODAS-gamma-CD in an acidic pH buffer of low molarity. Data illustrating the effects of capillary length and cyclodextrin concentration on the separation are presented. The longer capillary length and high voltage enabled the baseline separation of all isomers in less than 15 min. The optimized method was applied to the analysis of human control plasma containing labetalol utilizing solid-phase extraction (SPE) in the 96-well format.     

Chiral separations of basic drugs and quantitation of bupivacaine enantiomers in serum by capillary electrophoresis with modified cyclodextrin buffers.

Modified cyclodextrin derivatives were evaluated as the buffer additives in capillary electrophoresis of several racemic pharmaceutical bases. Uncoated and polyacrylamide-modified silica capillaries were compared for their effectiveness in the enantiomeric resolution and migration reproducibility of model solutes. Using cationic detergents in the mixed-micellar mode, optimized separations of the racemic drug bupivacaine are demonstrated in a spiked serum sample at the therapeutic level. Precision, linearity and sensitivity of the method appear adequate for reliable quantitation required in pharmacokinetic and clinical studies.     

Chiral separation of diastereomeric flavanone-7-O-glycosides in citrus by capillary electrophoresis

The 2S- and 2R-diastereomers of major flavanone-7-O-glycosides found in sweet orange (Citrus sinensis), mandarine (Citrus deliciosa), grapefruit (Citrus paradisi), lemon (Citrus limon), and sour or bitter orange juice (Citrus aurantium) were separated for the first time by chiral capillary electrophoresis (CE) employing various buffers with combined chiral selectors. Native cyclodextrins (CDs), neutral and charged CD derivatives were examined as chiral additives to the background electrolyte (BGE). Separation efficiency has not proved satisfactory with one single CD as chiral selector in the buffer, a full and simultaneous separation could often be achieved only by using combined buffer with two different CDs. Chiral separation of major flavanones in sweet orange, mandarine and grapefruit juices raised more difficulties than in lemon and sour orange juices as narirutin will not readily build complexes with most CDs. Diastereomeric flavanones of mature and immature grapefruits were compared and some differences were found: naringin showed different diastereomeric ratio and 2S-prunin appeared only in immature grapefruit. Marmalade was also examined by chiral CE. Its major flavanones corresponded to flavanone pattern of mixed sour and sweet oranges.