首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Mertzman MD  Foley JP 《Electrophoresis》2004,25(9):1188-1200
Cyclodextrin (CD)-modified microemulsion electrokinetic chromatography (MEEKC) or CD-MEEKC has not previously been applied to the area of chiral separations. Herein, the results of investigations of various microemulsions with CD additives are presented. Two different microemulsions are explored: an ethyl acetate sodium dodecyl sulfate microemulsion, and a chiral dodecoxycarbonylvaline (DDCV) microemulsion. Each microemulsion is paired separately with a neutral CD (hydroxypropyl-beta-CD) and an anionic CD (sulfated-beta-CD). In addition, the chiral DDCV microemulsion is investigated in both the R- and S- form. By varying simple parameters such as buffer system, applied voltage, surfactant enantiomer, and type of cyclodextrin, dramatic improvements in the chiral separations were noted. Resolution was found to be highly dependent on buffer identity and concentration, and somewhat dependent on whether the CDs used were randomly or highly sulfated. Under optimized conditions, the resolution ranged from 0.8 to 4.8, with plate counts ranging from 4000 to 26 000. Additionally, S- and R-levetiracetam, which had never before been enantioseparated via capillary electrophoresis (CE) methodologies, were separated in less than 8 min, with a resolution of 1.1.  相似文献   

2.
In this study, enantioseparations of five phenothiazines in cyclodextrin (CD)-modified micellar electrokinetic chromatography (MEKC) were investigated using a citrate buffer containing tetradecyltrimethylammonium bromide (TTAB) as a cationic surfactant at low pH. Beta-cyclodextrin (beta-CD) and hydroxylpropyl-beta-CD (HP-beta-CD) were selected as chiral selectors. The results indicate that the separation window is greatly enlarged by beta-CD concentration and that the separability and selectivity of phenothiazines are remarkably influenced by the concentrations of both beta-CD and TTAB, as well as buffer pH. The interaction of thioridazine with beta-CDs is considerably reduced in the presence of TTAB micelles due to competitive complexation of thioridazine with TTAB micelles, which is pH-dependent. As a result, effective enantioseparation of thioridazine is simultaneously achievable with that of trimeprazine and promethazine or ethopropazine in MEKC with addition of either beta-CD or HP-beta-CD, respectively, to a micellar citrate buffer containing TTAB at pH 3.5. Better enantioresolution of thioridazine in MEKC than in capillary zone electrophoresis can be obtained.  相似文献   

3.
A rapid and effective method was developed for the chiral separation of raltitrexed (RD) enantiomers by carboxymethyl-beta-cyclodextrin (CM-β-CD)-modified micellar electrokinetic chromatography (MEKC). Optimization of conditions including the type and concentration of the chiral selector, concentration of sodium dodecyl sulfate (SDS), pH and concentration of the background electrolyte (BGE), capillary temperature, and applied voltage was investigated. The enantiomers of raltitrexed could be separated with satisfactory resolution and linear response by using 75 mM Tris-phosphate at pH 8.0 containing 30 mM SDS and 8 mM CM-β-CD as buffer system. Furthermore, the usefulness of this method was demonstrated in a purity test of a real synthetic drug sample. Figure Chiral separation of raltitrexed by CM-β-CD MEKC was optimized and applied to test the purity of a synthetic drug sample  相似文献   

4.
5.
Jabor VA  Bonato PS 《Electrophoresis》2001,22(7):1399-1405
A capillary electrophoresis method for the simultaneous quantitation of praziquantel and its main metabolite trans-4-hydroxypraziquantel enantiomers in human plasma was developed and validated using cyclodextrin-modified micellar electrokinetic chromatography. Sample clean-up involved a single-step liquid-liquid extraction of plasma with toluene after the addition of NaCl. The complete enantioselective analysis was obtained in less than 7 min using 2% w/v sulfated beta-cyclodextrin as chiral selector and 20 mmol/L sodium deoxycholate as surfactant, in 20 mmol/L sodium borate buffer, pH 10. A 50 microm x 42 cm uncoated fused-silica capillary was used for the analysis, performed at a voltage of 18 kV and at 20 degrees C. The calibration curves were linear over the 125-625 ng/mL concentration range. The mean recoveries for praziquantel and trans-4-hydroxypraziquantel were up to 96 and 71%, respectively, with good precision. All four enantiomers were quantified at two concentration levels (200 and 600 ng/mL) with precision and accuracy below 15%. The quantitation limit was 50 ng/mL for (-)-(R)- and (+)-(S)-praziquantel and 62.5 ng/mL for (-)-(R)- and (+)-(S)-trans-4-hydroxypraziquantel, using 1 mL of human plasma.  相似文献   

6.
A chiral microemulsion electrokinetic chromatography method has been developed for the enantiomeric separation of 3,4-dihydroxyphenylalanine (dopa), its precursors phenylalanine and tyrosine, and the structurally related substance methyldopa. The separations were achieved using an oil-in-water microemulsion, which consisted of the oil-compound ethyl acetate, the surfactant sodium dodecylsulfate (SDS), the co-surfactant 1-butanol, the organic modifier propan-2-ol and 20mM phosphate buffer pH 2.5 or 2.0 as aqueous phase. For enantioseparation sulfated beta-cyclodextrin was added. The resolution of each racemate was optimized by varying the concentration of the buffer and all components of the microemulsion. Enantioseparation could be achieved for dl-dopa, dl-phenylalanine and dl-tyrosine within 13min with a resolution of 4.3, 3.1 and 3.3, respectively, and for methyldopa in 17min (Rs: 1.4). The established methods allowed the detection of dopa, phenylalanine, tyrosine and methyldopa with a limit at 0.5, 1.0, 0.2 and 2.0mug/ml.  相似文献   

7.
A micellar electrokinetic chromatography (MEKC) method was developed for the quantitation of polyphenols (+)-catechin and (-)-epicatechin (catechin monomers) and the methylxanthine theobromine in Theobroma cacao beans. Owing to the poor stability of catechin monomers in alkaline conditions, a 50 mM Britton-Robinson buffer at a pH 2.50 was preferred as the background electrolyte. Under these conditions, the addition of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) at a concentration of 12 mM to the SDS micellar solution (90 mM), resulted in a cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) endowed with two peculiar advantages compare to the conventional MEKC: (i) strong improvement of separation of the most important phytomarkers of T. cacao and (ii) enantioselectivity toward (+/-)-catechin. In particular, separation of methylxanthines (theobromine and caffeine), procyanidin dimers B1 and B2, and catechins (epicatechin and catechin) was obtained simultaneously to the enantioseparation of racemic catechin within 10min. The enantioselectivity of the method makes it suitable in evaluation of possible epimerisation at the C-2 position of epicatechin monomer potentially occurring during heat processing and storage of T. cacao beans. The extraction procedure of the phytomarkers from the beans was approached using ultrasonic bath under mild conditions optimized by a multivariate strategy. The method was validated for robustness, selectivity, sensitivity, linearity, range, accuracy and precision and it was applied to T. cacao beans from different countries; interestingly, the native enantiomer (+)-catechin was found in the beans whereas, for the first time we reported that in chocolate, predominantly (-)-catechin is present, probably yielded by epimerisation of (-)-epicatechin occurred during the manufacture of chocolate.  相似文献   

8.
A new micellar electrokinetic capillary chromatography method (MEKC) is proposed for the determination of ibuprofen and tetrazepam in human urine samples over a concentration range of therapeutic interest. A fused silica capillary (60 cm × 75 μm) is used. Ibuprofen and tetrazepam are detected via UV detection at 220 and 228 nm, respectively. Separation is performed at 25 °C and at a separation voltage of 30 kV, with 15 mM borate buffer (pH 10.2) containing 40 mM sodium dodecylsulfate as the electrolyte solution. Under these conditions the analytes were separated in <11 min. Sulfamethazine is used as an internal standard. Prior to determination, the samples are purified and enriched by means of an extraction–preconcentration step with a preconditioned C18 cartridge and by eluting the compounds with methanol. Good linearity, accuracy, precision, robustness and solution stability were achieved for the technique. Detection limits of 200 μg L−1 for ibuprofen and 300 μg L−1 for tetrazepam were obtained. These analytes were then determined in real urine using the technique.  相似文献   

9.
Eder AR  Chen JS  Arriaga EA 《Electrophoresis》2006,27(16):3263-3270
Doxorubicinol (DOXol) is a human metabolite of the chemotherapy agent doxorubicin (DOX), and is associated with dose-dependent cardiotoxicity and decreased drug efficacy. Due to the structural similarities and equal molecular charges of DOXol and DOX, their electrophoretic separation is commonly ineffective. A method for separating and detecting DOX and DOXol, as well as two DOXol enantiomers, was established using cyclodextrin-modified micellar electrokinetic capillary chromatography with laser-induced fluorescence detection. Differential DOXol production was detected in a DOX-sensitive and resistant pair of cell lines, with a 0.08 +/- 0.01 fmol limit of detection.  相似文献   

10.
Bitar Y  Holzgrabe U 《Electrophoresis》2007,28(15):2693-2700
CD-modified microemulsion EKC as a CE technique has been applied to the chiral separation of atropine, scopolamine, ipratropium and homatropine. Enantioseparations of these tropa alkaloids were optimized by using a standard oil-in-water (O/W) microemulsion and varying the nature and concentration of CD additives as well as of the organic modifier (methanol, 2-propanol or ACN) whilst keeping the applied voltage of 15 kV and capillary temperature of 30 degrees C constant. The standard (O/W) microemulsion BGE solution consisted of 0.8% w/w octane, 6.6% w/w 1-butanol, 2.0% w/w SDS and 90.6% w/w 10 mM sodium tetraborate buffer (pH 9.2). Enantioseparations with high resolution and short migration times of all tropa alkaloids were achieved by using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD and sulfated beta-CD in the microemulsion BGE and were superior to corresponding CD-modified CE methods.  相似文献   

11.
Gotti R  Fiori J  Hudaib M  Cavrini V 《Electrophoresis》2002,23(17):3084-3092
Separation of nine important alkyl methylbutyl- and isobutylamides (known as alkamides) obtained from Echinacea purpurea extracts was investigated by using cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC). Hydrophobic alkamides interact strongly with the micelles from the most common surfactants used in MEKC and this lead to predominant partition of the analytes into the micellar phase, resulting in poor resolution. The addition of neutral CDs to the alkaline (10 mM phosphate buffer pH 8.0) micellar system of sodium dodecyl sulfate (SDS), sodium cholate (SC) and sodium deoxycholate (SDC) was found to improve the separation of the studied alkamides. Among the several combinations surfactant/CD, three different systems showed to be particularly effective: SDS/hydroxypropyl-beta-CD (110 mM/100 mM) and SC/heptakis (2, 3, 6-tri-O-methyl)-beta-CD (200 mM/40 mM) which provided a complete separation of the studied compounds, and SDC/heptakis (2, 6-di-O-methyl)-beta-CD. The importance of appropriate surfactant vs. CD concentration ratio as well as that of total concentration of both surfactant and CD was considered. The optimization of the separation was performed by focussing the need for a rapid separation of nine alkamides diagnostically useful to define the fingerprint of Echinacea species.  相似文献   

12.
13.
14.
A method for the chiral separation of propiconazole using cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) with hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as chiral selector is reported. The use of a mixture of 30 mM HP-gamma-CD, 50mM SDS, methanol-acetonitrile 10%:5% (v/v) in 25 mM phosphate buffer solution was able to separate two enantiomeric pairs of propiconazole. Stacking- and sweeping-CD-MEKC under neutral pH (pH 7) and under acidic condition (pH 3.0) were used as two on-line preconcentration methods to increase detection sensitivity of propiconazole. Good repeatabilities in the migration time, peak area and peak height were obtained in terms of relative standard deviation (RSD). A sensitivity enhancement factor of 100-fold was achieved using sweeping-CD-MEKC at acidic pH. This is the first report on the separation of two pairs of propiconazole enantiomers and all the enantiomers of fenbuconazole and tebuconazole using sweeping-CD-MEKC. The limit of detection (S/N=3) for the three triazole fungicides ranged from 0.09 to 0.1 microg/mL, which is well below the maximum residue limits (MRL) set by Codex Alimentarius Commission (CAC). Combination of solid-phase extraction (SPE) pretreatment and sweeping-CD-MEKC procedure was applied to the determination of selected triazole fungicides in grapes samples spiked at concentration 10-40 times lower than the MRL established by the CAC. The average recoveries of the selected fungicides in spiked grapes samples were good, ranging from 73% to 109% with RSD of 9-12% (n=3).  相似文献   

15.
A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method was established for the determination of oleanolic acid and ursolic acid in cornel. The two components were separated in the running buffer of 40 mmol/L sodium borate containing 5% methanol, 25 mmol/L SDS and 15 mmol/L hydroxypropyl-beta-cyclodextrin (HP-beta-CD). The applied voltage was 24 kV. The wavelength of detection was 200 nm. The temperature was kept at 25 C. Cinnamic acid was used as the internal standard. The analytical performance of the method was tested with respect to linearity, precision and recovery. The calibration curves were linear in the range of 10.15-243.6 microg/mL, r=0.9993 (oleanolic acid) and 10.07-241.7 microg/mL, r=0.9994 (ursolic acid); the intra-day precision (RSD) was less than 3.7% (oleanolic acid) and 4.1% (ursolic acid); the inter-day precision (RSD) was less than 4.2% (oleanolic acid) and 4.9% (ursolic acid). The limits of detection were 1.6 microg/mL for both components. The method proved to be sensitive, rapid, accurate and suitable for the determination of oleanolic acid and ursolic acid in cornel.  相似文献   

16.
A cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) method has been developed and validated for purity determination of two bile acids, ursodeoxycholic acid (UDCA) and deoxycholic acid (DCA). Quantitation of related impurities such as lithocholic acid (LCA), chenodeoxycholic acid (CDCA), cholic acid (CA), and DCA in UDCA and CA in DCA was performed. A running buffer containing 20 mM borate-phosphate, 50 mM sodium dodecyl sulfate (SDS), 2.0 mM beta-cyclodextrin, and acetonitrile was used. Modifiers were added to improve resolution and selectivity. The applied voltage was 25 kV and detection was performed at 185 nm. Validation parameters such as selectivity, linearity, repeatability, intermediate precision, limit of detection, limit of quantitation, and robustness were evaluated. The method was simple and proved to be useful for the purity testing of bile acids in bulk drugs. Good results were obtained for related impurities at concentration levels from 0.05 to 1.5% with respect to the main component, according to international requirements.  相似文献   

17.
A method for the quantitative enantioselective analysis of amphetamine in human plasma by LC-HRMS is presented. High-resolution detection, alone and in combination with targeted MS/MS, was validated and compared to a highly sensitive GC-NICI-Method. Derivatization with (S)-N-(heptafluorobutyryl)-prolyl chloride was accomplished to yield derivatives suitable for enantioselective analysis of amphetamine on a nonchiral reversed phase column with MS-compatible mobile phase. Equal analytical performance was observed for the methods presented and the GC-NICI-MS method. A dynamic range of 4,000 was found for the established calibration curves. A fivefold deuterated analogue of both enantiomeres was used as an internal standard. Full validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, autosampler stability, matrix effect, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral application.  相似文献   

18.
In this study both native and chemically modified cyclodextrins (CDs) were investigated as buffer additives to improve the micellar electrokinetic capillary chromatography (MEKC) separation of endogenous bioanalytes in human urine. The following CDs were investigated: alpha, beta, gamma-CDs; hydroxypropyl-alpha-CD, hydroxypropyl-beta-CD, methylated beta-CD, sulphated beta-CD, sulphobutyl ether-beta-CD and hydroxypropyl-gamma-CD. The separations were compared to MEKC without additives. The best improvement in peak resolution and separation of urine components was observed with the sulphated beta-CD. A four-factor three-level full factorial design study was conducted on voltage, temperature, pH and sulphated beta-CD molarity. The optimum conditions were 25 mM sodium tetraborate, pH 9.5, 75 mM sodium dodecyl sulphate (SDS) and 6.25 mM sulphated beta-CD and were able to resolve 70 peaks from a urine pool in 12 min. These optimum conditions have been successfully applied to a number of clinical samples.  相似文献   

19.
A cyclodextrin-modified micellar electrokinetic chromatographic (CD-MEKC) method for the determination of the most important potential impurities of methotrexate (MTX): 2,4-diamino-6-(hydroxymethyl)pteridine, aminopterine hydrate, 4-[N-(2-amino-4-hydroxy-6-pteridinylmethyl)-N-methylamino] benzoic acid, 4-[N-(2,4-diamino-6-pteridinylmethyl)-N-methylamino] benzoic acid, and the distomer D-MTX is presented. The MEKC separation of these compounds was optimized by applying a step-by-step approach. The addition of beta-CD to a conventional MEKC system, based on sodium dodecyl sulfate (SDS) as surfactant, showed to be essential for the enantioresolution of racemic MTX as well as for the separation of the achiral impurities. To achieve high-resolution factor between the peaks adjacent to the main component (L-MTX), as required in the analysis of related impurities, the separation conditions were stressed; in particular, the addition of methanol to the CD-MEKC system resulted in a very effective choice. Under the optimized final conditions (100 mM SDS and 45 mM beta-CD in a mixture of 50 mM borate buffer, pH 9.30-methanol (75:25 v/v)), the method was validated showing a general adequate accuracy (93-106% recovery) in the determination of L-MTX related substances at the impurity level of 0.12% w/w with a relative standard deviation (RSD)% lower than 8% (n = 4). The method was successfully applied to the analysis of pharmaceuticals (tablets and injections) which showed to contain the distomer D-MTX as major impurity and aminopterine hydrate as a further related substance in the commercial tablets.  相似文献   

20.
Cyclodextrin-modified electrokinetic chromatography (CD-EKC) was investigated for the separation of 12 monomethylbenz[a]anthracene (MBA) isomers. Combined use of a polymeric surfactant, poly(sodium 10-undecenyl sulfate) (poly-SUS), with various types of neutral cyclodextrins (CDs) [beta-CD, gamma-CD, dimethyl-beta-CD (DM-beta-CD), trimethyl-beta-CD (TM-beta-CD) and hydroxypropyl-beta-CD (HP-beta-CD)] were successful in CD-EKC separation of the MBA isomers. Baseline resolution of 10 of the 12 isomers, except for 9-MBA and 2-MBA, was achieved with gamma-CD at pH 9.75. The beta-CD, gamma-CD, and beta-CD derivatives (DM-beta-CD, TM-beta-CD, HP-beta-CD) were found to have different resolution and selectivity. Additionally, the tR/t0 values of isomers were found to be dependent on the type and concentration of the CD additives. In general, tR/t0 values of MBA isomers decrease with an increase in the concentration of beta-CD derivatives, whereas the reversed was true when the concentrations of native beta-CD and gamma-CD were varied. The combination of 5 mM gamma-CD, 0.5% (w/v) poly-SUS, 35% (v/v) acetonitrile at a pH of 9.75 provided the best selectivity and resolution of the MBA isomers with a separation time of 110 min. However, the use of 30 mM DM-beta-CD under similar EKC conditions resulted in much faster separation (ca. 16 min) of 10 MBA isomers.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号