Physicochemical characterization of phosphinic pseudopeptides by capillary zone electrophoresis in highly acidic background electrolytes

Phosphinic pseudopeptides (i.e., peptide isosteres with one peptide bond replaced by a phosphinic acid moiety) were analyzed and physicochemically characterized by capillary zone electrophoresis in the pH range of 1.1-3.2, employing phosphoric, phosphinic, oxalic and dichloroacetic acids as background electrolyte (BGE) constituents. The acid dissociation constant (pK(a)) of phosphinate group in phosphinic pseudopeptides and ionic mobilities of these analytes were determined from the pH dependence of their effective electrophoretic mobilities corrected to standard temperature and constant ionic strength of the BGEs. It was shown that these corrections are necessary whenever precise mobility data at very low pH are to be determined. Additionally, it was found that the ionic mobilities of the phosphinic pseudopeptides and pK(a) of their phosphinate group are affected by the BGE constituent used. The variability of migration behavior of the pseudopeptides can be attributed to their ion-pairing formation with the BGE components.     

Use of cyclodextrins for the enantioselective separation of ergot alkaloids by capillary zone electrophoresis.

Ergot alkaloid enantiomer derivatives were resolved using capillary zone electrophoresis. The effect of cyclodextrins, added to the background electrolyte, on the migration time and the resolution was studied. Good separation for epimeric ergot alkaloid derivatives was also obtained using phosphate buffer at pH 2.5. Separation was improved by supplementing the background electrolyte with 30 mM of gamma-cyclodextrin. Good resolution of racemic ergot alkaloid derivatives in their enantiomers was achieved in a background electrolyte containing either beta-cyclodextrin or its derivative, or gamma-cyclodextrin.     

Analysis and characterization of phosphinic pseudopeptides by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was applied to analysis and characterization of phosphinic pseudopeptides with the general structure N-Ac-Val-Ala(psi)(PO2(-)-CH(2)) Leu-Xaa-NH(2), where Xaa represents one of 20 proteinogenic amino acid residues. Pseudopeptides containing neutral or acidic amino acid residues in position Xaa were analyzed as anions in weakly alkaline (pH 8.1) Tris-Tricine background electrolyte (BGE), pseudopeptides with basic amino acid residues in position Xaa were analyzed as cations in acid BGEs (Tris-phosphate buffers). Acidity of phosphinic acid moiety in peptides with basic amino acid residues was determined from the dependence of effective mobility of these peptides on pH in the acid pH region (pH 1.4-2.8). Additionally, separation of diastereomers of some peptides was achieved.     

区带毛细管电泳法分离测定洋金花中莨菪烷类生物碱

采用区带毛细管电泳法分离测定洋金花中3种莨菪烷类生物碱—阿托品、山莨菪碱和东莨菪碱。以57 cm×50μm熔融石英毛细管为分离通道,工作电压25 kV,温度25℃,200 mmol/L Tris-H3PO4(pH=8.3)为背景电解质。经优化分离条件,3种莨菪烷类生物碱达到基线分离,此方法快速、简便,可作为中药材洋金花中有效成分分离的方法和质量控制方法。     

Separation and determination of strychnine and brucine in Strychnos nux-vomica L. and its preparation by capillary zone electrophoresis

A capillary zone electrophoresis method was developed for the separation and determination of strychnine and brucine in Strychnos nux-vomica L. and its preparation. The factors that could affect the separation were studied, such as the types and concentrations of electrolytes, pH, ionic strength and organic modifier. The optimum running buffer was 20 mmol/L of ammonium acetate containing 0.2 mol/L of glacial acetic acid (pH 3.64). The applied voltage was 25 kV and the wavelength of the UV detector was set at 214 nm. The established method with dopamine hydrochloride as internal standard was linear in the range of 5-100 microg/mL for both strychnine and brucine. The recovery was 102.96% for strychnine and 98.56% for brucine. The extracts of Strychnos nux-vomica and its preparation could be directly injected for analysis.     

Determination of ephedrine alkaloids by capillary electrophoresis

A simple and rapid method for the simultaneous determination of six ephedrine alkaloids (ephedrine, pseudoephedrine, norephedrine, norpseudoephedrine, methylephedrine and methylpseudoephedrine) in Ephedrae herba by capillary electrophoresis was developed. A buffer solution that contained 0.005 M barium hydroxide and 0.02 M isoleucine and adjusted to pH 10.0 with ammonia solution was found to be the most suitable electrolyte for this separation. The contents of the six alkaloids in the crude drug of Ephedrae herba could be easily determined.     

Separation of nicotine metabolites by capillary zone electrophoresis and capillary zone electrophoresis/mass spectrometry

The use of capillary zone electrophoresis (CZE) and capillary zone electrophoresis/mass spectrometry (CZE/MS) has been demonstrated, in principle, for the separation of nicotine and nicotine metabolites. The buffer system developed for separation and detection by CZE/UV was modified for use in CZE/MS analysis. Several of the metabolites are isobaric and tandem mass spectrometric (MS/MS) techniques have been used to differentiate such analytes.     

Separation and partial characterization of Maillard reaction products by capillary zone electrophoresis

Capillary zone electrophoresis proved useful for separating small amounts of both charged and uncharged solutes that are otherwise difficult to analyse. A typical complex mixture that had previously resisted all analytical approaches, including reversed-phase separations, is the products arising from the reaction of free amino acids with aldehydic sugars (Maillard reaction products). By using capillary zone electrophoresis [untreated capillary 50 cm x 75 microns I.D., 18 kV, 0.02 mol/l phosphate buffer (pH 7.5)], a number of products resulting from the reaction of glucose or ribose with glycine, alanine and isoleucine were separated and partially characterized. They were separated (1) without derivatization (and profiles of compounds absorbing at 220 nm were obtained), (2) as phenylthiocarbamyl derivatives in a search for reactive amino groups and (3) after derivatzation with 2,4-dinitrophenylhydrazine in a search for a method for compounds with a free aldehydic group. Phenylthiocarbamyl derivatives were separated in 0.005 mol/l borate buffer (pH 9.6) at 20 kV and 25 microA. Separation of 2,4-dinitrophenylhydrazones was effected by electrokinetic micellar chromatography in the same apparatus using a 50 cm x 75 microns I.D. capillary at 10 kV in 0.01 mol/l Na2HPO4-0.006 mol/l tetraborate, 0.050 mol/l with respect to sodium dodecyl sulphate. The results are compared with those given by high-performance liquid and thin-layer chromatography.     

Enantiomeric separation by cyclodextrin modified capillary zone electrophoresis (CD-CZE) of quaternary tetrahydroprotoberberine alkaloids

A cyclodextrin modified capillary zone electrophoresis (CD-CZE) for the enantiomeric separation of tetrahydroprotoberberine N-metho salts was established. The resolution was optimized by changing the concentration of the electrolyte solution, hydroxypropyl-beta-CD (0.02 M, 0.07 M, or 0.14 M) or dimethyl-beta-CD (0.05 M or 0.15 M) in phosphate buffer (pH 2.5 or 3) containing 10% acetonitrile with an applied voltage of 20 kV. This method was applied toward the enantioselective bio-conversion of quaternary tetrahydroprotoberberine N-metho salts in cultured cells of Corydalis species.     

Separation and characterization of sub-microm- and microm-sized particles by capillary zone electrophoresis

The analytical separation and characterization of particles in the size range of sub-microm and microm diameters by capillary zone electrophoresis (CZE) has been reviewed. The theoretical basis, on which the mobility can be interpreted to provide information regarding characteristics of particle surface, has shortly been presented. Particular emphasis was put on the model dependence of that interpretation and the need in most applications to forego the classical idealized model of spherical particles with "smooth" surfaces and to apply more realistic models, which take the "hairy" surface of real particles into account. Some highlights of the literature on the CZE of polystyrene latex microspheres, organic and inorganic colloids, lipoprotein particles, viruses, liposomes, biological membrane vesicles, and biological cells have been discussed. Also summarized are the reports on the particle size dependence of mobility and peak broadening in CZE and on electrophoretic behavior of rodlike particles and particle aggregates. Finally, the effects of neutral polymers in the background electrolyte on particle mobility and peak width are reviewed.     

毛细管区带电泳法测定粉针剂中头孢拉定的含量

用毛细管区带电泳法测定头孢拉定的含量 ,未涂层毛细管柱 (75 μm×48.5cm ,有效长度 40cm) ,电压 2 8kV ,检测波长 2 3 0nm ,温度 2 0℃ ,进样 5×1 0 3Pa× 3s。运行缓冲液为 2 5mmol/L硼砂缓冲液。方法的线性范围 3 1 .2 2μg/mL～ 749.2 8μg/mL ,检测限为 1 .1 7μg/mL。     

Physicochemical characterization of a PEGylated liposomal drug formulation using capillary electrophoresis

In this work, the applicability of using CE to perform a physicochemical characterization of a PEGylated liposomal drug formulation of the anti-cancer agent oxaliplatin was examined. Characterization of the liposomal drug formulation using CE instrumentation encompassed: determination of the electrophoretic mobilities, size determination by Taylor dispersion analysis and interaction studies. Electrophoretic mobilities determined by CE were compared with the results obtained by laser Doppler electrophoresis, which were found to be subject to larger variation. Average hydrodynamic diameters of the liposome preparations, as determined by Taylor dispersion analysis, were in the range of 61-84 nm and were compared with the results obtained by dynamic light scattering. Interactions between oxaliplatin (and paracetamol) and the PEGylated liposome were non-detectable by CE frontal analysis as well as by liposome electrokinetic chromatography. In contrast, for the more lipophilic compound propranolol, apparent liposome-aqueous phase distribution coefficients (D(lip) ) were successfully determined by both electrokinetic chromatography (log?D(lip) =2.10) and by CE frontal analysis (log?D(lip) =2.14). It is envisioned that CE and capillary-based techniques, including Taylor dispersion analysis, will be useful tools for the characterization of nanoparticulate (e.g. liposomal) drug formulations.     

Separation of nitrophenols by capillary zone electrophoresis

Separation conditions suitable to a rapid resolution of a group of eight nitrophenols by capillary zone electrophoresis (CZE) were found. Required differences in their effective mobilities were achieved via host-guest complexation of -cyclodextrin combined with intermolecular interactions involved by polyvinylpyrrolidone. When both additives were present in the carrier electrolyte at pH=9.1 nitrophenols could be separated in the column of a, 300 m I.D. and 180 mm in the length within 8–9 minutes. It is shown that the column of such an I.D. providing enhanced sample load capacity, can operate with high separation efficiencies as maintaining zone dispersions due to Joule heating on a tolerable level. CZE on-line coupled with isotachophoretic sample pretreatment is shown to provide the concentration limits of detection at low ppb concentrations by using an on-column photometric detector operating at 254 and 405 nm detection wavelengths.     

Determination of rhodanese enzyme activity by capillary zone electrophoresis.

A new sensitive method has been developed for the determination of rhodanese activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of SCN- was monitored by sequential capillary zone electrophoretic runs. The determinations were performed in a 75-micron fused-silica capillary using 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, a separation voltage of 18 kV (negative polarity), a capillary temperature of 25 degrees C and direct detection at 200 nm. Short-end injection or long-end injection procedures were used for sample application. The method is rapid, able to be automated and requires only small amounts of sample and substrates, which is especially important in the case of highly toxic cyanide. The developed capillary electrophoretic method also has great potential for thiocyanate determinations in other applications.     

System zones in capillary zone electrophoresis.

This paper brings an overview of system zones (SZs) in capillary zone electrophoresis (CZE) and their effects upon the migration of zones of analytes. It is shown that the formation and migration of SZs is an inherent feature of CZE, and that it depends predominantly on the composition of an actual background electrolyte (BGE). One can distinguish between stationary SZs and migrating SZs. Stationary SZs, which move due to the electroosmotic flow only, are induced in any BGE by sample injection. Migrating SZs may be induced by a sample injection in BGEs which show at least one of the following features: (i) BGE contains two or more co-ions, (ii) BGE has low or high pH whereby H+ or OH- act as the second co-ion, and (iii) BGE contains multivalent weak acids or bases. SZs do not contain any analyte and show always BGE-like composition. They contain components of the BGE only and the concentrations of these components are different from their values in the original BGE. Providing that some of the ionic components of the BGE are visible by the detector, the migrating SZs can be detected and they are present as system peaks/dips in the electropherogram. It is shown that a migrating SZ may be characterized by its mobility, and examples are given how this mobility can depend on the composition of the BGE. Further, the effects of the migrating SZs (either visible or not visible by the detector) upon the zones of analytes are presented and the typical disturbances of the peaks (extra broadening, zig-zag form, schizophrenic behavior) are exemplified and discussed. Finally, some conclusions are presented how to cope with the SZs in practice. The proposed procedure is based on the theoretical predictions and/or measurements of the mobilities of SZs and on the so-called unsafe region. Then, such operational conditions should be selected where the unsafe region is outside of the required analytical window.     

Enantiomers resolution in capillary zone electrophoresis by using cyclodextrins.

Cyclodextrins added to the background electrolyte are shown to be useful for the resolution of racemic compounds in their enantiomers. Several parameters have to be controlled in order to achieve resolution, e.g., cyclodextrin type, concentration, analyte shape, as well as column temperature. The resolution of nor-epinephrine, epinephrine and isoproterenol in their enantiomers decreased by increasing the column temperature. Octopamine and ketamine have been resolved by supporting the background electrolyte with 2, 6-di-O-methyl-beta-cyclodextrin. In spite of the stronger inclusion-complex of ketamine than octopamine with the modified cyclodextrin its resolution was not satisfactory.     

毛细管区带电泳法拆分手性药物环扁桃酯

近年来,随着不同种类的手性添加剂[1]在毛细管电泳(CZE)中的使用,毛细管电泳越来越显示出其强有力的手性拆分性能。具有特殊笼状结构并含有多个手性中心的环糊精及其衍生物是毛细电泳手性分离研究中最常采用的手性添加添[2-4]。本文合成了环糊精衍生物单3 O 苯基胺甲酰基 β CD[2]并以之作为手性选择剂分离了β CD及手性药物环扁桃酯。1　实验部分932 3 HVPS高压电源(山东省化工研究院),DD 2000型可调波长紫外检测器(中国科学院大连化学物理研究所),XWT型记录仪(上海大华仪表厂),pHS 25型酸度计(上海雷磁仪器厂),石英毛细管45cm…     

A rapid urine creatinine assay by capillary zone electrophoresis.

Using capillary zone electrophoresis, the urine creatinine (uCr) assay was validated in extemporaneous diluted urine, both in healthy subjects and athletes, with the uCr concentration as a reference value to compare excretion rates of other metabolites in the same samples. The electrokinetic sample injection was carried out at 10 kV per 10 s; UV absorbance detection was at 254 nm. Using standard samples, the creatinine migration mean time in 100 mmol/L acetate buffer, pH 4.4, was 3.3+/-0.2 min; the repeatability for absolute migration mean time was 0.6% and peak height repeatability was 2.9%. The correlation coefficient of the standard curve was r = 0.999 and the detection limit was 23.1 micromol/L. Intra- and interassay coefficients of variation (CV) were 3.0 and 3.6%, respectively; recovery was 99+/-3% and linearity was r= 0.98. Normal urine samples were diluted 1:80 in run buffer. The present CE urine creatinine assay showed a good correlation with HPLC and with Jaffe methods (r = 0.98 and r = 0.97, respectively; p < 0.0001). The uCr in the morning urine samples of 34 healthy males (M), 38 healthy females (F), and 83 male athletes (A) was 10.4+/-6.1 mmol/L, 10.8+/-8.1 mmol/L and 13.2+/-6.5 mmol/L, respectively. The uCr difference (p < 0.02) between M and A and a correlation (p < 0.05) with age in A were observed.     

Application of capillary zone electrophoresis in the separation and determination of the principal gum opium alkaloids

We describe the use of capillary zone electrophoresis (CZE) for the qualitative and quantitative determination of major alkaloids (i.e., thebaine, codeine, morphine, papavarine and narcotine) in gum opium involving the analysis of alkaloids without derivatization or purification. Three extractions with 2.5% w/v aqueous acetic acid quantitatively extracted major alkaloids. The separation was carried out by CZE using a 7:3 mixture of methanol and sodium acetate (100 mM, pH 3.1) at a potential of 15 kV, with UV detection at 224 nm. Spiking of pure reference alkaloid standards in the opium extract was used for peak identification. The influences of buffer composition, pH and voltage on the separation of alkaloids were studied. The detection limit of each alkaloid dissolved in methanol was found to be 850 ng/mL (morphine), 450 ng/mL (thebaine), 500 ng/mL (codeine), 550 ng/mL (papaverine), and 500 ng/mL (narcotine) at an injection pressure of 300 mbar (injection volume, 4 nL) with a signal-to-noise ratio of 3:1. The external standard method was used for the quantification of alkaloids. The calibration plot was based on linear regression analysis. The relative standard deviation (RSD) for peak area and migration time was in the range of 1.03-3.56% and 0.34-0.69%, respectively. Percentage compositions (g%) of opium alkaloids in five gum opium samples were found to be in the range of 14.45-15.95 (morphine), 2.0-3.45 (codeine), 1.32-2.73 (thebaine), 0.92-2.37 (papavarine), and 3.85-5.77 (narcotine). The method developed is suitable for the routine analysis of major gum opium alkaloids in samples of forensic importance.