Separation and determination of the anthraquinones in Xanthophytum attopvensis pierre by nonaqueous capillary electrophoresis

A nonaqueous capillary electrophoresis (NACE) method with direct on-column UV detection has been developed for the separation of the pharmaceutically important anthraquinones from the total grass of Xanthophytum attopvensis pierre extract. The separation of three main anthraquinones (1-hydroxy-2-methoxy-3-hydroxymethyl-9, 10-anthraquinone-1-O-β-d-glucoside (1), rubiadin- 1-methylether (2) and 1-methoxy-2-formyl-3-hydroxy-9, 10-anthraquinone (3)) was optimized with respect to concentration of sodium cholate (SC) and acetic acid, addition of acetonitrile (ACN), and applied voltage. Baseline separation was obtained for the three analytes within 5 min using a running buffer containing 50 mM sodium cholate (SC), 1.0% acetic acid and 40% ACN in methanol. The method of NACE for the separation and determination of bioactive ingredient in traditional Chinese medicines was discussed.     

Separation and determination of aconitine alkaloids in traditional Chinese herbs by nonaqueous capillary electrophoresis

An easy, rapid, and simple nonaqueous capillary electrophoresis (NACE) method was developed for the identification and determination of three aconitine alkaloids, hypaconitine (HN), aconitine (AN), and mesaconitine (MN) within 6 min. The most suitable running buffer was composed of 60 mM ammonium acetate, 0.5% acetic acid, and 15% acetonitrile (ACN) in methanol with a fused-silica capillary column (50 cm x 75 microm ID). In the concentration range 12.5-1000 mg/L the calibration curves reveal linear relationships between the peak area for each analyte and its concentration (correlation coefficients: 0.9997 for HN, 0.9999 for AN, and 0.9995 for MN). The relative standard deviations of the migration time and peak area of the three alkaloids were 0.13, 0.57, 0.33 and 2.87, 1.06, 3.49%, respectively. The method was successfully applied to determine the three alkaloids in two commonly used traditional Chinese herbal medicines, the recoveries of the three constituents ranging between 94.7-101.9% for HN, 98.3-102.3% for AN, and 98.1-104.6% for MN.     

Separation of open-cage fullerenes using nonaqueous capillary electrophoresis

In this study, nonaqueous capillary electrophoresis (NACE) was used to separate three open-cage fullerenes. Trifluoroacetic acid (TFA) was used as the nonaqueous background electrolyte to change the analytes’ mobilities. The selectivity and separation efficiency were critically affected by the nature of the buffer system, the choice of organic solvent, and the concentrations of TFA and sodium acetate (NaOAc) in the background electrolyte. The optimized separation occurred using 200 mM TFA/20 mM NaOAc in MeOH/acetonitrile (10:90, v/v), providing highly efficient baseline separation of the open-cage fullerenes within 5 min. The migration time repeatability for the three analytes was less than 1% (relative standard deviation). Thus, NACE is a rapid, useful alternative to high-performance liquid chromatography for the separation of open-cage fullerenes.     

柱前衍生化-非水毛细管电泳法高效分离饮料中的脂肪醛

以9,10-菲醌作为柱前衍生试剂,采用非水毛细管电泳模式考察并优化了脂肪醛的分离条件。实验采用毛细管(总长58.5 cm,有效长度50 cm,内径50 μm),应用80 mmol/L NH4Ac、1.4 mol/L HAc缓冲体系,于20 ℃、5 kPa(50 mbar)下压力进样 8 s,在不加入其他添加剂的情况下,实现了7种脂肪醛的高效基线分离,检出限为0.37～0.87 μmol/L,线性范围为0.78～25 μmol/L。应用所建立的方法对实际样品进行了测定,结果令人满意。     

Separation and determination of 2,4-D, dicamba and 2,4,5-T in tobacco by nonaqueous capillary electrophoresis

A practical method for residue analysis of 2,4-D, dicamba and 2,4,5-T in baked tobacco leaves has been developed using nonaqueous CE (NACE). The herbicide residues of 2,4-D, dicamba and 2,4,5-T in tobaccos were extracted by ultrasonication with ethyl acetate, followed by a cleanup procedure with gel permeation chromatography. The separation of 2,4-D, dicamba and 2,4,5-T by NACE was optimized based on orthogonal experiment design with four factors at three levels. The optimal NACE condition was established with the running buffer of 40.0 mmol/L ammonium acetate in 90% CH3CN (apparent pH 10.2), and the applied voltage of -25 kV over a capillary of 50 microm id x 46 cm (37.5 cm to the detector window), which gave a baseline separation of 2,4-D, dicamba and 2,4,5-T within 15 min. The LOD were ca. 0.4-0.6 microg/mL for the three herbicides, whereas the overall recovery ranged from 80.8 to 84.1%. The proposed method has been successfully applied to measure 300 real tobacco samples, and the residue profiles of the three herbicides in tobacco samples were obtained and evaluated.     

Separation and determination of active components in Radix Salviae miltiorrhizae and its medicinal preparations by nonaqueous capillary electrophoresis

A nonaqueous capillary electrophoresis (NACE) method was developed for simultaneous assay of three bioactive components (1: cryptotanshinone; 2: tanshinone IIA, and 3: tanshinone I) in Radix Salviae miltiorrhizae and in its herbal preparations for the first time. After optimization of separation conditions, a buffer of 250 mmol L(-1) ammonium acetate containing 30% acetonitrile and 1.0% acetic acid (V:V) in methanol was selected for separating the three analytes, but baseline separation of tanshinon I and tanshinone IIA was not obtained. Therefore second-order derivative electropherograms were applied for resolving overlapping peaks. Regression equations revealed good linear relationships (correlation coefficients 0.9943-0.9991) between peak heights in second-order derivative electropherograms and concentrations of the three analytes. The relative standard deviations (RSD) of the migration times and the peak height of the three constituents were in the range of 0.81 -0.88% and 0.34-1.13% (intra-day), 1.57-1.86% and 3.05-5.52% (inter-day), respectively. The recoveries of three constituents ranged from 90.2 to 108.5%. The results indicated that baseline separation of the analytes was sometimes hard to obtain and second-order derivative electropherograms were applicable for the resolving and analysis of overlapping peaks.     

Separation and determination of homologues of linear alkylbenzenesulfonates by nonaqueous capillary zone electrophoresis using alkylammonium salts in ethanol

The separation of linear alkylbenzene sulfonates (LAS) by nonaqueous capillary electrophoresis (NACE) using negative polarity, and a buffer containing acetic acid and an alkylamine in nonaqueous ethanol, has been investigated. Several primary, secondary, and tertiary alkylamines with alkyl chains of different length were compared. The solutes travelled against the electroosmotic flow (EOF), and at the same time were braked by association with the alkylamine molecules or with the alkylammonium ions. The best resolution between adjacent LAS homologues (R approximately 2.1), partial isomer resolution in two peaks, and at the same time an excellent repeatability, was obtained with a small dipentylamine excess over the acetic acid. When the buffer concentration increased, resolution between the homologues increased slightly (R approximately 2.4), and a different isomer group was partially separated. A background electrolyte (BGE) containing 10 mM acetic acid and 20 mM dipentylamine to separate and quantify the homologues within 25 min is recommended. The isomer peak profile with up to three peaks can be estimated using this buffer and another one with 80 mM acetic acid and 90 mM dipentylamine. The former BGE was used to determine LAS in liquid and powder laundry detergents. The detection limit for the determination of total LAS in these products was 2.5 microg mL(-1), and the peak area and migration time interday repeatabilities were below 4.3 and 2.8%, respectively.     

Separation of transition metals in nonaqueous media with capillary electrophoresis

The separation of transition metal Ni2+, Cu2+, Co2+, Zn2+, Cd2+ and Fe3+ in methanol was investigated by using different types of organic acids as complexing agents. In pure methanol, the weaker and simpler acetic, propionic, butyric and valeric acids could enhance metal ions selectivity by increasing acid concentration and metal ions could be separated with high efficiency. However, hydroxycarboxylic acids obviously made separation efficiency worse. The effect of mixed organic acids, mixture solvent (methanol-acetonitrile, methanol-water) on metal ions separation was discussed further. The advantages of using nonaqueous solvent over aqueous for metal ions separation were shown finally.     

Separation of linoleic acid oxidation products by micellar electrokinetic capillary chromatography and nonaqueous capillary electrophoresis

In this work the suitability of micellar electrokinetic capillary chromatography (MEKC) and nonaqueous capillary electrophoresis (CE) to the analysis of the primary oxidation products of linoleic acid was studied with uncoated fused-silica capillaries. The primary autoxidation products of linoleic acid are the four hydroperoxide isomers 13-hydroperoxy-cis-9, trans-11-octadecadienoic acid, 13-hydroperoxy-trans-9, trans-11-octadecadienoic acid, 9-hydroperoxy-trans-10,cis-12-octadecadienoic acid, 9-hydroperoxy-trans-10, trans-12-octadecadienoic acid. Addition of a surfactant such as sodium dodecyl sulfate (SDS) or sodium cholate (SC) into the running buffer (20-30 mM 3-(cyclohexylamino)-1-propanesulfonic acid (CAPS) or ammonium acetate, pH 9.5-11) was required to enhance the water solubility of the sample and selectivity of the separation. MEKC proved to be a promising new technique for the separation of the primary oxidation products of lipids giving results comparable to high performance liquid chromatography (HPLC). Partial separation of hydroperoxide isomers was also achieved using nonaqueous CE with methanol-acetonitrile-sodium cholate as running buffer.     

Enantiomeric separations by nonaqueous capillary electrophoresis

This paper reviews the recent advances in enantioseparations by nonaqueous capillary electrophoresis (NACE) and the effect of organic solvents on mobility of enantiomers, separation selectivity and resolution. In general, the enantioseparation systems in NACE are similar to those of aqueous capillary electrophoresis (CE) except pure organic solvents are used. The influence of important parameters such as concentration and type of chiral selectors, apparent pH, ionic strength, temperature, and control of electroosmotic flow is discussed. In addition, the reported applications of NACE separations of racemates are presented.     

Separation of phospholipids by capillary zone electrophoresis with indirect ultraviolet detection

A simple method for separation of different anionic and zwitterionic phospholipid classes by capillary zone electrophoresis (CZE), using indirect UV detection with adenosine monophosphate (AMP) as background electrolyte and the UV-absorbing additive, was successfully developed in this study. The separation conditions including apparent pH (pH*) of running buffer, concentration of AMP, organic solvent, applied voltage and capillary temperature were systematically optimized. The application of this method to human blood sample was also briefly examined.     

Analysis of steroids by nonaqueous capillary electrophoresis

A simple method for the separation and determination of steroids (estradiol valerate, triamcinolone, levonorgestrel and ethinylestradiol) in single and compound tablets by nonaqueous capillary electrophoresis with ultraviolet (UV) spectrophotometric detection has been developed for the first time. After optimizing the electrophoretic parameters, including the nature of electrolytes and composition of organic solvent, the running buffers of methanol-acetonitrile (95: 5, v/v) containing 20 mM sodium acetate (pH 6.5) and methanol-acetonitrile (90: 10, v/v) containing 25 mM sodium acetate (pH 7.0) were found to be most suitable for determining estradiol valerate and triamcinolone, respectively. Reliable separation and simultaneous determination of levonorgestrel and ethinylestradiol were achieved in methanol containing 20 mM of ammonium acetate and 10 mM of sodium dodecyl sulfate (SDS). Tamoxifen was used as internal standard. Performance of the method, including migration time and peak area reproducibility, linearity, sensitivity and accuracy, were also evaluated. The limits of detection (S/N = 3) for four analytes were in the range of 9.8–19.5 μ g/mL. The relative standard deviations (RSD) of the migration times and peak areas of the analytes were in the range of 0.14–1.0% and 0.7–2.7% (intraday), 0.5–2.8% and 1.5–4.2% (interday), respectively. Within the tested concentration range, linear relationships between peak area ratios and concentrations of the analytes were obtained (correlation coefficients: 0.9987–0.9996). The method has been successfully applied to the determination of ingredients with recoveries over the range of 96.6–100.6%. The text was submitted by the authors in English.     

非水毛细管电泳测定黄连饮片中5种生物碱

建立了一种非水毛细管电泳(NACE)同时测定黄连饮片生品与炮制品中小檗碱、巴马汀、药根碱、木兰碱和黄连碱含量的方法。分别考察了非水溶剂、缓冲液体系及其浓度和pH、运行电压、运行温度和检测波长等条件对实验结果的影响。在优化的实验条件下,选择非水毛细管电泳分离模式,以40 mmol/L乙酸钠-40 mmol/L乙酸铵的无水甲醇缓冲溶液(pH 5.8)为电泳介质,未涂渍标准熔融石英毛细管(64.5 cm×75 μm,有效长度56 cm)为分离通道,检测波长为254 nm,分离电压为25 kV,压力进样(5 kPa×6 s),柱温为20 ℃。结果显示,5种生物碱在20 min内可实现基线分离,加标回收率为98.37%～101.03%。该方法简单、准确,重现性较好,可用于黄连饮片内在质量的评价和控制。     

Separation and determination of flavonoids in Ixeridium gracile by capillary electrophoresis

A simple and rapid capillary electrophoresis method has been developed for the quantitative analysis of three active compounds: (3R)-7,2'-dihydroxy-3',4'-dimethoxy-isoflavan, kaempferol, and quercetin in Ixeridium gracile. The buffer solution used in this method is 20 mmol/L borate at pH 9.5. The effects of pH value, borate concentration, and applied voltage on migration behavior are systematically investigated. Regression equations reveal good linear relationships (correlation coefficients: 0.9986, 0.9997, and 0.9999) between the peak area of each compound and its concentration. The relative standard deviations of the migration time and peak area are less 1.12% and 3.11% (intraday), and 1.43% and 3.52% (interday), respectively, under the optimized separation conditions. The contents of the three flavonoids in I. gracile are successfully determined within 7.8 min, with satisfactory repeatability and recovery.     

Recent advances in nonaqueous capillary electrophoresis

Nonaqueous capillary electrophoresis is undergoing rapid development. The scope of the investigations has clearly expanded, covering both basic studies and analytical applications. This review provides a comprehensive overview at the current status of the technique. Special attention is given to theoretical, methodological, and technical challenges, and the achievements of capillary electrophoresis in nonaqueous media are demonstrated with reference to recent applications.     

Efficiency studies in nonaqueous capillary electrophoresis

Nonaqueous capillary electrophoresis (NACE) is a relatively new area with several advantages that include enhanced efficiency and improved detection sensitivity. The goal of this study was to investigate the influence of NACE compared to aqueous CE on the separation efficiency of oligosaccharides. The applied voltage and buffer concentration were optimized for the aqueous and nonaqueous buffer media to minimize the band broadening effects of Joule heating and electrophoretic dispersion. At the optimized conditions a 1.5-fold enhancement in efficiency was obtained with the nonaqueous buffer medium.     

Stacking for nonaqueous capillary electrophoresis

Nonaqueous capillary electrophoresis (NACE) is a useful mode in CE for separation and quantification of hydrophobic compounds. However, because of the low conductivity of most of the organic solutions, stacking is not used often in this technique and the sample volume is very limited. As a result of the small sample volume, the detection limits are poor. Furthermore, NACE is affected greatly by the presence of salts in the sample. Here, we show that transient isotachophoresis (t-ITP) can be used easily in this type of electrophoresis to enhance the detection limits and also to reverse the deleterious effects of salts in the sample. Several factors, which affect the stacking in this type of electrophoresis, are described. For example, the presence of salts in the organic solvent, type of sample introduction, and the solvent for the terminating ion were all found to have profound effects on the degree of concentration. Furthermore, the separation time can be shortened by t-ITP.     

Rapid determination of momordicoside in Momoradica charantia seeds by capillary zone electrophoresis

A novel method is described for the rapid determination of momordicoside in bitter melon based on capillary zone electrophoresis. Electrophoresis conditions, including the pH value and concentration of running buffer, as well as the voltage applied were optimized. The contents of momordicoside in 52 samples originating from different agricultural areas in China were determined. The results showed an excellent linearity in the concentration range of 0.50–2.51 mg mL^?1 for all samples (R ²?>?0.9999), with a recovery of 96.0% and a relative standard deviation of 1.4%. The method is characterized by rapidity, accuracy, the need for small samples only, and is suitable for analyses at a large scale.     

Separation and determination of cations in beverage products by capillary zone electrophoresis

Cation determination is important for quality control of beverage products. To determine a large group simultaneously, a capillary electrophoresis procedure is developed with indirect UV at 214 nm in a three-complex buffer system (10 mM N,N-dimethylbenzylamine (DBA), 8 mM lactic acid and 2 mM 18-crown-6) with good mobility matching with desired cations. Under optimized conditions with pH adjusted to 4.65, a baseline separation is achieved for 14 cations (Rb(+), NH(4)(+), K(+), Ca(2+), Na(+), Mg(2+), Mn(2+), Co(2+), Fe(2+), Cd(2+), Cr(3+), Ni(2+), Zn(2+) and Cu(2+)) within 7 min using an uncoated silica column. To cover ng/l to mug/l range, both hydrostatic and electrokinetic sampling are studied, showing working ranges within (0.05-50)/(0.005-2) microg/l and detection limits (13-78)/(1.4-10) ng/l, respectively with satisfactory repeatability (RSD 0.31-0.47% for migration time, and 3.0-4.0% for peak height measurement). Agreeable results with established inductively coupled plasma-atomic emission spectrometry method have been obtained for orange juice and tea samples.     

Separation and simultaneous determination of quinolone antibiotics by capillary zone electrophoresis

Summary The potential of capillary zone electrophoresis has been investigated for the separation and quantitative determination of some quinolone antibiotics. The influence of different conditions, such as the nature and concentration of the electrophoretic electrolyte, on migration time, peak symmetry, efficiency and resolution was studied. A buffer consisting of 100mm HEPES adjusted to pH 8.5 containing 10% (v/v) acetonitrile was found to furnish a very efficient and stable electrophoretic system for the separation of exoxacin, ciprofloxacin, ofloxacin, oxolinic acid, nalidixic acid and pipemedic acid. A linear relationship between concentration and peak area for each compound was obtained in the concentration range 0.25–40 μg mL⁻¹; detection limits were approximately 0.25 ng mL⁻¹. It was demonstrated that the method can be used for the simultaneous determination of these six antibiotics in serum and urine samples.