荔枝中水溶性维生素的毛细管电泳快速分离分析

本研究通过双模对接高压电源实现了毛细管电泳中0～40 kV及以上的超高电压。通过考察电压、缓冲溶液浓度、pH等对分离的影响,确定了优化的实验条件。结果表明,在40 kV的超高电压下,缓冲液为25 mmol/L硼砂-H3BO3溶液(pH 8.8),8种水溶性维生素(VB1、VB2、VB6、VC、D-泛酸钙、D-生物素和烟酸、叶酸)在2.2 min内获得了较好的基线分离。同时对荔枝中的水溶性维生素进行定量分析得到了令人满意的结果。     

毛细管电泳法高压快速分离分析菠菜中的水溶性维生素

在毛细管电泳法中,通过双模对接高压电源可以获得0～40 kV甚至40 kV以上的超高电压。本研究在40 kV的超高电压下,以纯电解质水溶液为缓冲液,实现了蔬菜中通常含有的8种水溶性维生素(VB1、VB2、VB6、VC、D-泛酸钙、D-生物素、烟酸和叶酸)的快速分离及菠菜样品的定量分析。通过考察电压、缓冲溶液浓度、pH值等因素对分离的影响,确定了优化的实验条件。结果表明,在40 kV高压下,采用25 mmol/L硼砂-硼酸溶液缓冲液(pH 8.8),菠菜中上述8种水溶性维生素在2.2 min内获得了较好的基线分离。用此方法对菠菜中的水溶性维生素进行定量分析,得到了令人满意的结果。水溶性维生素的线性相关系数范围为0.9981～0.9999,检出限为0.2～0.3 mg/L,在菠菜中的平均加标回收率为88.0%～100.6%,峰面积的相对标准偏差(RSD)为1.15%～4.13%。     

Nonaqueous media for separation of nonionic organic compounds by capillary electrophoresis

For the separation of neutral compounds by micellar electrokinetic chromatography, separations are usually carried out in predominantly aqueous solution in order to preserve the charged micelle necessary for the separation. We now show that polycyclic aromatic hydrocarbon (PAH) compounds can be separated efficiently by capillary electrophoresis in pure methanol or in aqueous-organic mixtures containing a high percentage of methanol. Sodium tetradecyl sulfate was the preferred surfactant. The effects of pH, solvent composition, surfactant structure, and surfactant concentration on the separations were studied. Reproducible migration times and linear calibration plots were obtained.     

改良型单纯形法优化硝基喜树碱的毛细管电泳分离

使用改良型单纯形法优化硝基喜树碱(Nitrocamprothecinum,NC)一对同分异构体的毛细管电泳分离。考察了运行电压、缓冲液的pH、硼砂和十二烷基磺酸钠(SDS)的浓度等4个影响因子,与传统的单因子优化方法及其结果进行比较。改良型单纯形法(采用CRS函数为响应函数)在分析方法的建立过程中显著减少了实验步骤,获得了更好的电泳分离条件。     

Application of capillary zone electrophoresis for separation of water-soluble gold monolayer-protected clusters

An effective capillary electrophoretic technique for separating samples of negatively charged, polydisperse, water-soluble gold monolayer-protected cluster (Au MPC) protected by monolayers of N-acetyl-L-cysteine has been developed. The separation mechanisms of the Au MPC in CZE suggest that the larger core sizes Au MPC emerge first from the capillary. The electrophoretic separation depends on pH, buffer concentration, and organic modifiers. The addition of aliphatic alcohols to the run buffer can improve the separation of Au MPC by reducing the EOF and changing the selectivity between the Au MPCs. The enhancement of resolution is attributed to the more significant difference in the charge-to-size ratio between the Au MPCs. The run buffer containing 20 v/v % ethanol provides the best separation for water-soluble Au MPC. Our proposed CE method provides a powerful tool to evaluate and separate the water-soluble Au MPC products.     

毛细管电泳在手性化合物分离分析中的研究进展

手性化合物的对映异构体往往表现出不同的生理活性,因此建立手性化合物的有效分离分析方法具有重要意义。毛细管电泳(CE)是一种分离效率高、分析速度快、样品用量少、分离模式灵活多样的分离分析方法,在手性化合物的分离和检测领域应用广泛。该文主要综述了2017～2019年CE在手性分离分析方面的最新进展,并对其未来的发展趋势进行了展望。     

Elimination of adsorption effects in the analysis of water-soluble vitamins in pharmaceutical formulations by capillary electrophoresis.

A tendency to an increase in migration times was observed when different water-soluble vitamins were analysed repeatedly in pharmaceutical preparations by capillary electrophoresis. In order to better understand the origin of this effect, the influence of the vitamins and the excipients, such as cellulose derivatives, was investigated. These studies indicated that the increase in analyte migration times was most probably due to the adsorption of different kinds of constituents to the capillary wall. Different rinsing procedures were tested in order to eliminate these unfavourable effects. A rinse of the capillary with a 25 mM sodium dodecyl sulfate (SDS) solution in the running buffer between successive runs was found to be particularly effective when the analysis was performed by free solution capillary zone electrophoresis (CZE). When the vitamins were determined by micellar electrokinetic chromatography (MEKC) using SDS as surfactant, a short capillary rinse with the running buffer was sufficient to obtain reproducible migration times. The CZE and MEKC methods developed were validated and compared. Both methods could be applied to the determination of water-soluble vitamins in different multivitamin formulations.     

Analysis of water-soluble vitamins by micellar electrokinetic capillary chromatography

Seven water-soluble vitamins were determined simultaneously by micellar electrokinetic capillary chromatography with UV detection. All these compounds were separated from each other within ca. 22 min by using a carrier containing sodium dodecyl sulphate as the surfactant. On-column detection at 254 nm with ethyl p-aminobenzoate as the internal standard allowed sensitive, accurate and reproducible determination of these compounds. Five principal constituents of a vitamin injection were determined with relative standard deviations of less than 2.1%.     

Comparison of three different anionic surfactants for the separation of hydrophobic compounds by nonaqueous capillary electrophoresis

The effect of the three different surfactants, sodium dodecyl sulfate (SDS), diethylhexyl sodium sulfosuccinate (AOT), and taurodexycholic acid sodium salt (STDC) on the nonaqueous capillary electrophoretic separations of hydrophobic compounds were compared with formamide containing 20 mM K2HPO4 as electrolyte solvent. Separations of all selected uncharged hydrophobic compounds, e.g., p-arylacetophones were shown to be strongly dependent on the kind of surfactant. The electrolyte containing 180 mM SDS provided the best result for the selected samples.     

Tailoring the separation selectivity of metal complexes and organometallic compounds resolved by capillary electrophoresis using auxiliary separation processes

The use of auxiliary separation mechanisms to manipulate the separation selectivity of metal complexes and organometallic species is reviewed. Auxiliary separation mechanisms included in the review are micellar electrokinetic capillary chromatography, ion-pairing and ion-exchange electrokinetic chromatography. This paper discusses how these secondary mechanisms can be effectively employed to tailor separation selectivity.     

The role of organic solvents in the separation of nonionic compounds by capillary electrophoresis

Although nonionic compounds can be separated by micellar electrokinetic chromatography (MEKC), application of this technique is restricted by a somewhat limited elution range. Incorporation of organic solvents in the background electrolyte (BGE) greatly extends the scope of MEKC and provides a major variable in optimizing the separation of neutral analytes. This paper provides a systematic review of the principles and scope of the separation of neutral analytes by capillary electrophoresis (CE) in organic-aqueous solution. The methods surveyed include those that use tetraalkylammonium salts, dioctyl sulfosuccinate, lauryl poly(oxyethylene) sulfate. Polyaromatic hydrocarbon (PAH) compounds can be separated using sodium hexadecyl sulfate in 70% methanol (30% aqueous) to 100% methanol.     

Combinatorial enantiomeric separation of diverse compounds using capillary array electrophoresis

Combinatorial chiral separations were performed on a 96-capillary array electrophoresis system. A comprehensive enantioseparation protocol employing neutral and sulfated cyclodextrins as chiral selectors for common basic, neutral and acidic compounds was developed. By using only four judiciously chosen separation buffers, successful enantioseparations were achieved for 49 out of 54 test compounds spanning a large variety of pK and structures. Therefore, unknown compounds can be screened in this manner to identify the optimal enantioselective conditions in just one run.     

Strategy for the separation of concentrated samples by capillary electrophoresis

The use of concentrated samples is usually avoided during conventional separations since utilization of concentrated samples normally compromises the quality of separation. However, in case of the detection of low‐abundance components, highly concentrated samples are necessary, which leads to an extremely high concentration for high‐abundant components. This will make the separation difficult due to the serious longitudinal dispersion. Here, we developed a method to separate high concentration of components based on the modified capillary electrophoresis. The mechanism involves concentrated sample stretched into a wider zone in the higher electric field strength; the sample zone is fractionated into thin sections via a cutting effect; these thin sections are then separated. Based on this mechanism, we examined to separate an overloaded mixture of N ,N ′‐diphenylguanidine and N ,N ′‐di(o‐tolyl)guanidine. Baseline separation was achieved due to much small longitudinal dispersion. The theoretical plate numbers of peaks were around 3.5 × 10⁵ m⁻¹. The practicality of the new approach is demonstrated in the separation of a model protein mixture, containing lysozyme, bovine serum albumin, and ribonuclease A.     

Enantiomeric separation of synthetic 2,3-dihydroxy-3-phenylpropionate compounds by beta-cyclodextrin-modified capillary electrophoresis

A new capillary electrophoretic method was developed for enantiomeric separation and optical impurity analysis of three synthetic 2,3-dihydroxy-3-phenylpropionate compounds using native beta-cyclodextrin (beta-CD) as chiral selector and borate as a background electrolyte. The separation was carried out in uncoated capillary (58.5 cm x 75 microm I.D., effective length 48.5 cm). The results showed that beta-CD as the chiral selector exhibited good enantioselectivity and the baseline separation was obtained at pH 9.8, 200 mM borate buffer containing 1.7% beta-CD at applied voltage 15 kV and capillary temperature 20 degrees C within 15 min. The precision of each tested compound was less than 1.0% at migration time and 5.0% in corrected peak area and the accuracy of the method was in the range of 98.7-105%. Furthermore, the developed method was successfully applied to the determination of the undesirable trace (2S,3R)-(+)-form impurity in the synthetic (2R,3S)-(-)-2,3-dihydroxy-3-phenylpropionate samples.     

Determination of vanillin and related flavor compounds in cocoa drink by capillary electrophoresis

In the first part of this study, the stability of five terpenes (alpha-pinene, limonene, camphor, citronellol, and carvacrol) under subcritical water conditions was investigated. The stability studies were carried out at four different temperatures (100, 150, 200, and 250 degrees C) with two different heating times (30 and 300 min). When water temperature was increased, the degradation of terpenes became more serious. Prolonged exposure time to each heating temperature also caused decreased terpene stability. The terpene recoveries were determined by conducting subcritical water extraction of sand spiked with terpenes. The recoveries are typically around 70 to 80% for extractions at 100 degrees C. Terpene recoveries were decreased with increasing water temperature due to poorer stability of terpenes. After the degradation and recovery studies, basil and oregano leaves were extracted using water at both 100 and 150 degrees C. The concentrations of each individual terpene in the water extract generally ranged from trace quantity to 65 microg terpene/g herb. However, the concentration of carvacrol in the oregano-water extract at 150 degrees C was found to be as high as 4270 microg carvacrol/g oregano.     

Chiral separation of cetirizine by capillary electrophoresis

Chiral separation of cetirizine, a second-generation H(1)-antagonist, was studied by CD-mediated CE. Several parameters, including pH, CD type, buffer concentration, type of co-ion, applied voltage and temperature, were investigated. The best conditions for chiral separation were obtained using a 75 mM triethanolamine-phosphate buffer (pH 2.5) containing 0.4 mg/mL heptakis(2,3-diacetyl-6-sulfato)-beta-CD and 10% ACN. Online UV detection was performed at 214 nm, a voltage of 20 kV was applied and the capillary was temperature controlled at 25 degrees C by liquid cooling. Hydrodynamic injection was performed for 1 s. The method was validated for the quantification of levocetirizine in tablets and for enantiomeric purity testing of the drug substance. Selectivity, linearity, LOD and LOQ, precision and accuracy were evaluated for both methods. The amount of levocetirizine dihydrochloride in the commercially available tablets was quantified and was found to be within the specification limits of the claimed amount (5 mg). The amount of distomer in levocetirizine drug substance was found to be 0.87 +/- 0.09% w/w, which is in agreement with the certificate of analysis supplied by the company.     

Novel approach for the rapid determination of water-soluble organic acids in wine by co-electroosmotic flow capillary zone electrophoresis

An innovative protocol for the fast analysis of some organic acids in red wine by co-electroosmotic capillary zone electrophoresis and indirect UV detection using hexadimethrine bromide (HDB) as coating agent was proposed. The adsorption of HDB onto the capillary wall provided a stable electroosmotic flow and separation of small anions was carried out using background electrolytes containing no polymer additive. Low RSD% values (<3.6%) in terms of migration times and effective mobilities were obtained from the analysis of a mixture of nitrate and nitrite and of a mixture of organic acids. An experimental design approach was used to investigate the effects of temperature, separation voltage, and percentage of methanol added to the running buffer solution on the separation of the analytes. A faster method allowing the separation of the organic acids involved in the malolactic fermentation of wine was developed. Using a running electrolyte consisting of 35% (v/v) methanol in a solution of 22 mM benzoic acid at pH 6.10 adjusted with 1.0 M TRIS-base buffer, the separation of tartaric, malic, succinic, acetic, and lactic acids was feasible in less than 210 s. Application of the method to the quantification of the above-mentioned organic acids in Italian red wine samples is reported.     

Chiral separation of 3,4-methylenedioxymeth- amphetamine and related compounds in clandestine tablets and urine samples by capillary electrophoresis/fluorescence spectroscopy

The R-(-)- and S-(+)-isomers of 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) were prepared, identified by gas chromatography/mass spectrometry (GC/MS) and then used as standards in a series of capillary electrophoresis (CE) experiments. Using these R-(-)- and S-(+)-isomers, the distribution of (RS)-MDA and (RS)-MDMA stereoisomers in clandestine tablets and suspect urine samples were identified. Several electrophoretic parameters, such as the concentration of beta-cyclodextrin used in the electrophoretic separation and the amount of organic solvents required for the separation, were optimized.