LC with a Teicoplanin Aglycone Chiral Sorbent for the Separation of the Enantiomers of Non-Steroidal Anti-Inflammatory Drugs: An Evaluation of Chiral Capillary Columns

A capillary column with a teicoplanin aglycone (TAG) stationary phase (CSP) was used for enantioselective separation of selected profen non-steroidal anti-inflammatory drugs in capillary liquid chromatography (cLC). The effect of variations in the mobile phase composition on the retention and enantioselective separation was examined. The best resolution was attained in the mobile phase composed of 40/60 (v/v) methanol/1.0% triethylamine acetate buffer, pH 4.0 or 4.5. Under the optimized separation conditions, five of the set of eight analytes were enantioresolved with resolution values better than 0.9. Only fenoprofen was not enantioseparated in any system tested. The optimized separation conditions were used for evaluation of three chiral capillary columns (all prepared in the same way in our laboratory) in terms of the repeatability and reproducibility of the results. The run-to-run repeatability was expressed in terms of the relative standard deviation (RSD) values, obtained from ten independent measurements, for the following parameters: the retention factor for the first eluted enantiomer (k ₁), the selectivity (α), the enantioresolution (R), the theoretical plate count per meter for the first eluted enantiomer (N ₁) and the elution curve asymmetry for the first eluted enantiomer (As ₁). None of the RSD values exceeded 8%. The column-to-column reproducibility of these parameters ranged between 1 and 9%. The results obtained with TAG based CSPs in cLC (a laboratory packed capillary column) were compared with those obtained by classical high-performance liquid chromatography (HPLC) with a commercially available column. The cLC procedure provided a better enantioresolution and the elution curves had a better symmetry.     

毛细管电泳手性拆分喹诺酮类药物对映体

采用毛细管电泳法,以铜(Ⅱ)-L-异白氨酸为手性拆分剂,同时分离了氧氟沙星、洛美沙星、司帕沙星和加替沙星四种喹诺酮类药物对映体.考察了手性拆分剂的种类、配比和浓度,缓冲溶液的种类、浓度和pH值,有机添加剂的种类和用量,分离电压等试验条件对分离效果的影响.含8 mmol·L-1L-异白氨酸和4 mmol·L-1硫酸铜的pH 8.5的30 mmol·L-1硼酸钠-盐酸缓冲溶液中,氧氟沙星和加替沙星对映体实现分离;在含20 mmol·L-1 L-异白氨酸,10 mmol·L-1硫酸铜和乙腈(5+95)的pH 9.0的20 mmol·L-1的Tris-硼酸钠缓冲溶液中,司帕沙星、洛美沙星和加替沙星对映体同时实现完全分离.     

非水毛细管电泳对9种手性药物的拆分

用非水毛细管电泳成功地分离了洛贝林、托吡卡胺、普萘洛尔、阿替洛尔、环扁桃酯、沙丁胺醇、苯海索、芬氟拉明和异丙嗪等9种手性化合物。以甲酰胺为介质、柠檬酸-三羟甲基氨基甲烷(Tris)为电解质、在254 nm波长下紫外检测。对手性选择剂的类型及浓度、背景电解质的pH值以及离子强度等因素对分离的影响做了系统的研究,最后确立了9种手性药物的最佳分离条件。实验发现,不同的手性选择剂对手性药物具有不同的分离选择性;每一种选择剂都存在一个相对水相体系较高的最佳浓度值而使分离效果最佳;在非水体系中,最佳pH值要比在水相体     

毛细管电泳法手性拆分4种氨酸和2种手性药物对映体

以双(6-氧-β-羧甲基-1,4-丁烯二酸单酯)-β-环糊精(DOCB-β-CD）作为手性添加剂,利用毛细管电泳对氨基酸和手性药物对映体进行拆分研究。 以20 mmol/L磷酸盐为缓冲溶液,考察了手性添加剂的浓度及缓冲溶液的pH值与分离电压等对拆分效果的影响,并在其优化条件下,实现了4种DL-氨基酸（苯丙氨酸、色氨酸、酪氨酸和组氨酸）以及手性药物（罗格列酮和酮洛芬）对映体的基线分离。     

高效毛细管电泳-电导检测拆分联萘酚对映体

手性拆分;高效毛细管电泳-电导检测拆分联萘酚对映体     

Multivariate Optimization Approach for Chiral Resolution of Chlorophenoxy Acid Herbicides Using Teicoplanin as Chiral Selector in Capillary LC

In this paper, the selectivity and resolution of enantiomeric separation by capillary liquid chromatography (cLC) of racemates of phenoxy acid herbicides are modelled. The compounds studied were 2-(±)-(2,4,5-trichlorophenoxy)propanoic acid (2,4,5-TP), 2-(±)-(2,4-dichlorophenoxy)propanoic acid (2,4-DP), 2-(±)-(4-chloro-2-methyl)phenoxypropanoic acid (MCPP) and 2-(±)-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid] (diclofop acid), using a capillary column packed with silica particles modified with teicoplanin as chiral selector. Several mixtures of methanol (MeOH), water and triethylamine acetate (TEAA) buffer at different pHs have been tested as mobile phases, and experimental parameters such as resolution (Rs), retention factor (k) and enantioselectivity factor (α) have been measured in all tested conditions. The chemometric methods used to explore and to model the data were principal component analysis (PCA), stepwise multiple linear regression (stepwise-MLR) and response surface analysis (RSA). The results show that it is possible to quantitatively predict the quality of enantiomeric separations of related compounds in a given chromatographic system.     

Separation of Enantiomers of Drugs by Capillary Electrophoresis with Permethyl‐gamma‐Cyclodextrin as Chiral Solvating Agent

High‐throughput screening is a promising new approach in analytical chemistry. Within the framework of an extended screening program (The German‐Chinese Drug Screening Program), the enantioseparation of 86 drugs was investigated by capillary zone electrophoresis in the presence of the chiral solvating agent (CSA) octakis‐(2,3,6‐tri‐O‐methyl)‐γ‐cyclodextrin (TM‐γ‐CD). By this means, 15 drugs could be separated into enantiomeric pairs. Approximate measures for the degree of interaction (migration retardation factor, R_m) and for the degree of enantiomer recognition (migration separation factors, α_m) revealed intriguing patterns that were compared with those found for native γ‐cyclodextrin (γ‐CD). Although there is a distinct influence of the analyte structure on the electrophoretic data, interpretation remains difficult. Most remarkably, permethylation of γ‐CD leads neither to a higher affinity nor to better chiral recognition, in contrast to the findings with α‐CD.     

奥美拉唑、兰索拉唑对映体及相关物质在不同手性柱的分离比较

考察了奥美拉唑、兰索拉唑对映体及其拆分剂联二萘酚在4种手性柱（chiralcel OD、chiralpak AD、kromasil CHI-TBB和chiral-AGP)上的色谱行为。实验结果表明：Chiralpak AD、 Chiral-AGP柱分离度大，柱效稳定，并且这两种柱子的配合使用实现了对包结拆分的全过程监控。此外，本文根据对映体在不同手性柱的出峰顺序进行了讨论。     

Determination of Non-Steroidal Anti-Inflammatory Drugs in Natural Waters Using Off-Line and On-Line SPE Followed by LC Coupled with DAD-MS

Two different procedures for simultaneous determination of six NSAIDs (diflunisal, diclofenac, fenoprofen, ibuprofen, naproxen and tolmetin) in environmental waters are described. Final analysis of target compounds is performed by reversed-phase liquid chromatography – diode array detection and mass spectrometry (HPLC-DAD and LC-MS), whereas sample preparation is based on solid-phase extraction (SPE). A variety of sorbents and their respective advantages and disadvantages are discussed. For the off-line SPE of NSAIDs from water samples, a LiChrolut RP-18 was selected out of all investigated sorbents. In case of on-line coupling of SPE with chromatographic system LiChrosphere RP-18 was selected as the best one in terms of recovery of NSAIDs evaluated, RSD and availability. The applicability of the method was also evaluated. Method detection limits were in the range of 0.7−94 ng L⁻¹. Recoveries ranged from 96 to 109% and relative standard deviations were lower than 5%. The procedures were shown to be linear over a wide range of concentration, exhibited satisfactory repeatability and accuracy, and reached limits of detection in the low ng L⁻¹ range. No breakthrough volume was observed neither for off-line SPE (in the studied range of 100, 200, 300, 500, 700, 1000 and 2000 mL of tap water sample) nor for on-line SPE (in the wide range of 10 mL, 20 mL, 30 mL, 50 mL, 70 mL, 100 mL and 200 mL of tap water sample).     

Chiral Separation of Ofloxacin Enantiomers by Microchip Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection

We describe a chiral separation method for ofloxacin enantiomers, levofloxacin and dextrofloxacin by microchip capillary electrophoresis with capacitively coupled contactless conductivity detection. The running buffer included 1 mmol L^?1 MES and 1 mmol L^?1 Tris (pH 8.0) with a separation voltage of 1.5 kV and an injection time of 10s. Under these conditions, the enantiomers were completely separated within 1 min. The linear calibration curves were A = 5.76 c — 0.00587 for levofloxacin and A = 5.41 c — 0.00551 for dextrofloxacin, in which the linear concentration of the components all ranged from 0.05 to 0.15 mg mL^?1 (regression coefficients were both 0.9996). The limits of detection (S/N = 3) were, respectively, 18 and 21 μg mL^?1. The relative standard deviations of migration time were both 2.0% (n = 6). The relative standard deviations of peak area were 3.4% (n = 6) for levofloxacin and 4.0% (n = 6) for dextrofloxacin. The effects of some factors on resolutions, such as separation voltage and injection time, concentration of running buffers, were studied. The method was simple, rapid, high‐efficient. Furthermore, the method could be applied to the chiral separation of the product containing these enantiomers, such as Ofloxacin Eye Drops.     

毛细管电泳分离盐酸美西律对映体机理的研究

探讨了环糊精对美国西律对映体手性识别的机理，对毛细管电泳手性分离选择系数ａ值和环糊精包结常数的计算方法做了修正，计算了甲基化β环糊精与对映体形成包结络合物的稳定常数和手性分离过程中的热力学参数，并对由该方法计算的结果进行了分析，结果表明，环糊精对美西律对映体包结常数的大小顺序与它们的手性分离选择相相反，但是，手性分离过程中的焓变（△（△Ｈ）和熵变（△（△Ｓ））越大，手性分离选择性也越大，根据计算结     

NMR Investigation of the Interaction of Three Non-Steroidal Anti-Inflammatory Drugs with Human Serum Albumin

The understanding of the interaction between non-steroidal anti-inflammatory drugs and human serum albumin plays a fundamental role in the development of new drugs and new therapeutic strategies. Several studies have been performed, nevertheless, the interaction phenomena are still not fully understood. In this work, high-field solution Nuclear Magnetic Resonance (NMR) spectroscopy was applied to compare the strength of the interaction of diclofenac sodium salt, ketorolac tris salt and flurbiprofen sodium salt toward albumin. To this aim, mono- and bi-selective relaxation rate measurements were performed by applying selective π-pulses at the selected frequencies and by following magnetization recovery. On the basis of the dependence of relaxation parameters on albumin concentration, normalized affinity indexes were calculated for several protons of the drugs. Affinity indexes for diclofenac were about five-fold higher in comparison with ketorolac and flurbiprofen. Aromatic moieties of the three drugs and methine protons at the chiral centers of ketorolac and flurbiprofen were more involved in the interaction with albumin. In conclusion, NMR spectroscopy allows not only for the comparison of drug-to-protein affinities but also points out the nature of the drug sites that are more extensively involved in the interaction.     

5种手性药物毛细管电泳对映体拆分

采用α、β、γ－环糊精和二甲基、羟丙基－β－环糊精等６种中性环糊精为手性添加剂,在毛细管电泳分离中,进行了５种手性中心具有相似特点的碱性药物对映体的拆分研究。详细地讨论了环糊精类型及其浓度、pＨ值、分离电压、操作温度、以及有机添加剂等操作参数对药物对映体拆分的影响。     

Simultaneous Chiral Separation of Geometry Isomers and Enantiomers of Nateglinide by Capillary Electrophoresis with Mixture of CD Derivations as Chiral Selector

Abstract

A capillary electrophoresis (CE) method for the simultaneous separation of geometry isomers and enantiomers of nateglinide was built. Several different dyclodextrin (CD) derivatives were tested for the chiral separation of nateglinide, and it was proved that ionic CDs [i.e., carboxymethy-β-CD (CM-β-CD) and sulphonic-β-CD (S-β-CD)] could show better chiral selectivity for both geometry isomers and enantiomers than the neutral CDs. The separation of geometry of both isomers and enantiomers of nateglinide was obtained by CE in a 75-µm i.d. × 60 cm (effective length 45 cm) fused-silica capillary at 11 kV voltage, while 30 mM phosphate (pH = 8.38) acted as running buffer and a mixture of 40 mM S-β-CD + 21 mM CM-β-CD served as chiral selector. The detective wavelength was set at 254 nm.     

Evaluation of the Enantiomeric Separation of Dipeptides Using a Chiral Crown Ether LC Column

Abstract

The direct optical resolution of six dipeptides into four stereoisomers each was achieved on an enantioselective crown ether column. An inclusion complex is formed between the stationary phase and the solute when using an acidic mobile phase. The acidic mobile phase serves to protonate the requisite primary amine of the dipeptide thereby allowing an attractive interaction between the ammonium functional group and the oxygens of the crown ether. Due to the differences in stability of the complexes formed, the four optical isomers elute at different times allowing the stereoisomeric separation. One of the factors affecting enantioselectivity is the distance between the primary amine functional group and the stereogenic center of the chiral moiety. Dipeptides are particularly useful molecules for the studying this “distance effect” since the bonding order of the two amino acids can be reversed. In addition to the enantiomeric separations of dipeptides possessing two stereogenic centers, the behavior of dipeptide separations possessing only one chiral center (i.e., with achiral glycine as one of the residues) is examined to gain additional insight into the mechanism and the effect of the proximity of the primary amine group to the chiral center.     

Detection and Separation of Free Amino Acid Enantiomers by Capillary Electrophoresis with a Chiral Crown Ether and Indirect Photometric Detection

18-Crown-6 tetracarboxylic acid (18C6H₄) has been successfully used as a chiral selector for capillary electrophoretic (CE), high-performance liquid chromatographic (HPLC), and gas chromatographic (GC) separation of the enantiomers of DL-amino compounds. We have previously used X-ray crystallographic analysis and HPLC with an immobilized 18C6H₄ chiral stationary phase to study chiral recognition by 18C6H₄ of several DL amino acids (DL-AA). In this study CE was used for chiral recognition of several DL-AA in electrolyte solution containing 18C6H₄, in which the analyte (D or L amino acid) interacts freely. Among 14 DL-AA investigated, the enantiomers of nine (Glu, Ile, Met, PheG, Phe, Ser, Tyr, Val, and Thr) were successfully recognized in 4-15 mM 18C6H₄. Indirect photometric detection with a cationic dye, chrysoidine, was used to monitor non-chromophoric DL-AA. Among nine successfully recognized DL-AA, the D forms of Ser, Thr and Met migrated faster than the corresponding L forms. The strengths of interactions predicted from the order of migration of each enantiomer in CE were different from those in HPLC analysis. The different enantiomer recognition probably can be ascribed to the difference between CE in which the selector is not immobilized and HPLC in which the selector is immobilized by means of a spacer.     

Separation of the Enantiomers of Thyroxine by HPLC with Chiral Mobile Phases

A high-performance liquid chromatographic (HPLC) method has been developed for separation of the enantiomers of thyroxine (T4). A silica gel column was used in conjunction with a chiral mobile phase (CMP) comprising 35:65 (v/v) acetonitrile–water containing 0.1 mM copper(II) acetate, 0.2 mM L-proline, and 0.5 mM triethylamine (TEA), pH 5.42. The flow rate was 1.0 mL min^?1 and the analysis temperature 40 °C. L-T4 was eluted before D-T4 by mobile phase containing L-proline copper complex. Inversion of the chirality of the mobile phase resulted in reversal of this order of elution. A racemic mobile phase containing DL-proline copper complex resulted in no separation. The enantioseparation phenomenon is discussed. When the method was used to determine the concentration of T4 enantiomers in the serum of a patients with thyroid disease, different concentrations of T4 enantiomers were found in different patents.