Application Of Cyclodextrins In Chiral Separations By Capillary Electrochromatography

Capillary electrochromatography (CEC) is a new and efficient micro-separationtechnology by highly combination of chromatography and electrophoresis. In recentyears, CEC has quickly become one of the most promising analytical and separationtechniques in chiral separation science, because of the rapid, efficient, low-cost,environmentally friendly features. Capillary columns are "heart" for chiral separationin CEC. The separation materials and the preparation of chiral stationary phases (CSP)are the focus of the capillary column research. In this paper the object is to developethe novel capillary electrochromatographic columns for chiral separations ofdifferentenantiomers by CEC. Several capillary columns were prepared by chemicalbonding commonly used chiral β-cyclodextrin (β-CD) selectors modified by variousfunctional groups with as chiral ligands. These CEC columns with novel cyclodextrinligand have the advantage of rapid enantioseparations, good reproducibility and so on.Their structures were characterization by infrared spectroscopy (IR), scanningelectron microscopy (SEM) and other related means. By using novel β-cyclodextrincolumns, the rapid, efficient, low-cost of the new motheds for the enantioseparationsof common cardiovascular drugs enantiomers such as β-blockers and calcium channelblockers were first established by capillary electrochromatography. The new methodswere preliminarily used for the determinations of enantiomers in tablets and humanplasma. The above study has been reported for the first time. The study work on chiralcapillary chromatography includes the following sections:1. It is summary of the recent chiral separation methods and preparation methodsof chiral stationary phases, which focuses on the relevant developments ofcyclodextrin derivative for the separation of chiral drugs by capillaryelectrochromatography. All above would provide the research basis of this thesis.2. A mono-ethylenediamine-β-cyclodextrin was synthesized and first bonded tothe surface of ordered mesoporous material SBA-15in order to obtain a chiralstationary phase (EACDP) with stable urea bond for capillary electrochromatography.The novel separation material was uniformly packed into a piece of fused silicacapillary column by using slurry packing method and fabrication fitter of organicploymers in situ techniques. The chemical structure and morphology of new columnwere characterized. The porosity and electroosmotic flow (EOF) of new column were measured. The results showed that new kind of β-cyclodextrin-based SBA-15columnhas good permeability and can generate stable and enough electroosmotic flow forCEC. The EACDP column was employed for the enantioseparations of β-blockerschiral drugs by electrically driven flow in polar organic mode. The10kinds ofcommonly used in clinical β-blockers enantiomers such propranolol etc wereseparated under optimized conditions. The enantioresolutions of propranolol andarotinolol were1.96and1.99, respectively. The study found that the main factors ofchiral separations were inclusion interation of the cyclodextrin cavitybetween with thesolutes and the hydrogen bonding at the substituent port. The preminary determinationof propranolol enantiomers in tablet obtained satisfactory results by the proposedmethod. Capillary electrochromatography can greatly reduce solvent consumption andthe cost of test, which has a broad application prospects.there is a range ofapplications.reduce costs and3. The separation and determination methods of calcium antagonists includingmanidipine hydrochloride and nicardipine hydrochloride enantiomers were developedby open-tubular capillary electrochromatography (O-CEC), respectively. A newcapillary column (SCDP) with p-nitrophenylcarbamation β-cyclodextrin was preparedby sol-gel method. The preparation method was simple without packing procedureand burning column fittings. The sol-gel column modified with cyclodextrinderivative has higher column capacity and separation reproducibility. Thecyclodextrin ligand and mercapto group (-SH) were introduced by sol-gel procedure.Then the–SH group was coverted into negative sulfonic group (-SO3-) by moderateoxidization, which faciliate to the enhancement of EOF. The open tublar column waspreliminarily characterized by infrared spectroscopy (IR) and scanning electronmicroscopy (SEM). In polar organic mode, the effect of the content of organicsolvents, the volume fraction and concentration of added triethyl amine and glacialacetic acid, the operating voltage, the temperature on resolution (RS) were investigated.The better enantioseparations and reproducilities of manidipine hydrochloride andnicardipine hydrochloride on the O-CEC column were achieved within5min and7min, respectively. For example, the intra-day RSDs of retention times were0.4%and1.0%for the two manidipine enantiomers. And the intra-day RSDs of peak areas were3.2and4.5%(n=5). The CEC method has several advantages, including preparingsimple, rapid, good reproducibility, and low reagent consumption.4. A new sulfobutyl ether-β-cyclodextrin open-tubular capillary electro chromatography (O-CEC) was prepared by sol-gel technique, in which the negativesulfobutyl could increase the EOF. The enantioseparation and determination newmethod of nicardipine hydrochloride in plasma were established by using theopen-tubular CEC column (SECDP). The fast separation of nicardipine hydrochlorideenantiomers was achieved about15min (Rs=4.08) by the synergistic effects ofsulfobutylether-β-cyclodextrin (SBE-β-CD) in both the stationary and mobile phases.A good linear relationship was observed in the range of0.5~50.0μg/mL fornicardipine hydrochloride enantiomers. The detection limts of nicardipine were0.1μg/mLfor its two enantiomers. By compared with the reported literatures, the CECmethod has a good resolution, high column efficiency, short analysis time and lessreagent consumption. Moreover, the preparation of the column is simple, betterpracticability, which will be of great benefit to the pharmacokinetics research of chiraldrugs for the human.5. By using glycidyl methacrylate polymer as matrix in situ, the sulfobutylether-β-cyclodextrin was modified to the inner wall of capillary column and obtaineda kind of more stable open-tubular CEC column (SECDP). Its basic structure wascharacterized by infrared spectroscopy (IR) and scanning electron microscopy (SEM).The sulfonic acid group can provide enough and stable positive electroosmotic flow.The good enantioseparations of10kinds of chiral dihydropyridine drugs includingnicardipine were achieved by synergistic effects of sulfobutylether-β-cyclodextrin inthe stationary phase and mobile phases. Based on the above chromatographic data, therelated chiral separation mechanism was also discussed. The results indicated thatvarious interactions such as inclusion, hydrogen-bonding and electrostatic attractionwith dihydropyridine drugs together contributed the chiral separations.The abovemethod is suitable for fast enantioseparation and montoring of chiral dihydropyridinedrugs. It has important significance for perfect quality control system of chiral drugs.