阴离子选择性耗尽进样-胶束扫集毛细管电泳法对痕量醋酸氢化可的松的测定

联用阴离子选择性耗尽进样和胶束扫集两种在线富集技术,建立了胶束毛细管电泳方法测定化妆品中醋酸氢化可的松的方法。讨论了SDS浓度、样品基体、进样电压、进水时间和进样时间对富集和分离的影响。优化的实验条件:以120 mmol/L SDS-20 mmol/L NaH2PO4(pH2.2)-10%(体积分数)甲醇为缓冲体系,分离电压-20 kV,进样电压-20 kV,进样时间80 s,进水时间200 s,测量波长250 nm。在该实验条件下,醋酸氢化可的松的富集倍数比普通毛细管电泳法提高了约173倍。方法的线性范围为0.05~5.0 mg/L,检出限为12.6μg/L。该方法用于化妆品中醋酸氢化可的松含量的测定,回收率为98%~105%,相对标准偏差均小于4.0%(n=4)。     

离子液体作为添加剂的反向微乳毛细管电动色谱分析化妆品中的糖皮质激素

建立了以离子液体为添加剂的反向微乳毛细管电泳(IL-MEEKC)法分离测定化妆品中氢化可的松、泼尼松和醋酸氢化可的松3种糖皮质激素的方法.微乳毛细管电泳的最佳缓冲体系组成为:2.4% SDS+6.6%正丁醇+0.5%正辛烷+35 mmol/L BMIM-BF4+20 mmol/L磷酸二氢钠缓冲液(pH 2.2);运行电...     

场放大进样-胶束毛细管电泳法测定化妆品中3种糖皮质激素

采用场放大进样-胶束毛细管电泳法对化妆品中氢化可的松、泼尼松和乙酸氢化可的松3种糖皮质激素进行了分离测定。电泳介质为0.20mmol.L-1硼砂缓冲溶液(pH 9.0),运行电压为-20kV,进样电压-20kV,进样时间45s,进水压力3kPa,进水时间20s,检测波长250nm。在优化试验条件下,氢化可的松、泼尼松和乙酸氢化可的松的检出限分别(3S/N)为0.015,0.017,0.017mg.L-1。应用此方法分析了化妆品样品,测得回收率在93.8%～107%之间,测定值的相对标准偏差(n=5)均小于5.1%。     

鼠李糖脂应用于微乳毛细管电动色谱快速测定化妆品中激素类物质

采用生物表面活性剂鼠李糖脂建立了无需助表面活性剂的微乳体系,并应用于微乳毛细管电动色谱快速分析化妆品中皮质类激素泼尼松、泼尼松龙和氢化可的松。考察了pH值、鼠李糖脂浓度、离子强度、油相种类和浓度、分离温度、分离电压及进样电压和时间的影响,得出微乳体系最佳组成为0.1%(w/w)鼠李糖脂+0.8%(w/w)正庚烷+99.1%(w/w)硼砂缓冲液(80 mmol/L,pH 9.2)。分离温度20℃,分离电压20kV,电动进样10 kV×3 s,泼尼松、氢化可的松和泼尼松龙在9.4 min内可基线分离。重复进样7次,迁移时间和峰面积的RSD分别小于0.2%和5.0%。3种分析物线性范围均为5～100 mg/L;检出限分别为1.0,1.1和1.3 mg/L(S/N=3)。仅需简单萃取即可用于化妆品样品测定,回收率为81.6%～108%;RSD均小于4.8%。     

连花清瘟胶囊中6种有效成分的毛细管胶束电动色谱法测定

建立了毛细管胶束电动色谱法同时测定中药复方制剂连花清瘟胶囊中甘草苷、芦丁、金丝桃苷、槲皮苷、绿原酸、大黄酸6种药效成分含量的分析方法.使用未涂层弹性石英毛细管,以50 mmol/L SDS-15mmol/L磷酸氢二钠-15 mmol/L硼酸(含25%异丙醇,pH=8.0)作电解质,于254 nm下紫外检测,被测组分在3...     

胶束电动毛细管色谱间接紫外光检测法分离胆汁酸

利用间接紫外光检测法在254 nm进行胆汁酸胶束电动毛细管色谱分离的研究.在对氨基苯磺酸为背景电解质和十二烷基硫酸钠作胶束的体系中,加入高浓度的尿素,有效地改善了两类胆汁酸5组份的分离度,在优化分离缓冲体系10 mmol/L对氨基苯磺酸-5 mmol/L硼砂-30 mmol/LSDS-7 mol/L尿素-10%乙醇(pH 7.5)中,13 min内获得基线分离,分离效率为8.4×104～1.1×105.所建立的方法无需衍生化处理,为胆汁酸的分离提供了新的通用的方法.     

胶束电动毛细管电泳法分离分析呋喃西林及其制备杂质

建立了分离分析呋喃西林及其制备杂质5-硝基糠醛二乙酯的胶束电动毛细管电泳法。考察了缓冲液的种类、浓度和p H,十二烷基硫酸钠(SDS)的浓度以及分离电压等因素对分离结果的影响。在20 mmol/L SDS-10 mmol/L Na H2PO4(p H 7.0)、分离电压15 k V的优化条件下,在10 min内即可实现分离分析。呋喃西林在5~3000μg/m L范围内、5-硝基糠醛二乙酯在2~40μg/m L范围内均呈现良好的线性关系,相关系数(r2)均大于0.9977,呋喃西林和5-硝基糠醛二乙酯的定量限分别为5μg/m L和2μg/m L,回收率为96.0%~100.2%,相对标准偏差为0.94%~3.7%。方法已应用于实际样品的分析。     

胶束电动毛细管色谱法鉴别蓝色圆珠笔油墨

建立了用胶束电动毛细管色谱法（MECC）对纸上微量蓝色圆珠笔油墨进行分析鉴别的方法。研究了检测波长、电压、温度及电泳缓冲液中各组分浓度等因素对圆珠笔油墨分离的影响。当电压为25kV、柱温为25℃，检测波长为200nm时，以50mmol/L SDS-50mmol/L硼砂溶液（外加体积分数为45％的乙腈）为缓冲液，20种微量圆珠笔油墨样品样到了良好的鉴别。     

胶束电动毛细管色谱法分析辣椒制品中5种苏丹红

建立了同时测定辣椒粉、辣椒油和辣椒酱中苏丹红Ⅰ,Ⅱ,Ⅲ,Ⅳ,G的胶束电动毛细管电泳分析方法,样品经正己烷提取、中性氧化铝柱净化、再经丙酮-正己烷(5∶95,V/V)洗脱,经氮气吹干、乙腈溶解,用40 mmol/L硼砂-40 mmol/L SDS按1∶2的比例稀释后进样。运行缓冲液为2.5 mmol/L硼砂-30 mmol/L SDS-40%乙腈(p H 9.2)。5种色素在13 min内达到基线分离,标准曲线线性范围为1~20 mg/L,线性关系良好(r>0.997),检出限范围为0.12~0.62μg/m L,定量限范围为2.4~12.4 mg/kg。加标回收率为76.3%~98.6%,相对标准偏差(RSD)小于5%。     

离子液体和β-环糊精修饰反向微乳毛细管电动色谱分析化妆品中的激素

建立了以离子液体和β-环糊精为添加剂的反向微乳毛细管电泳(MEEKC)法分离测定化妆品中丙酸氟替卡松、曲安奈德、醋酸可的松、地塞米松、氢化可的松和泼尼松6种激素的方法.在优化的实验条件下,6种物质于12min内达到基线分离,丙酸氟替卡松在2.0～200mg/L范围内线性关系良好,其它组分在2.0 ～ 500mg/L范围内线性关系良好,检出限(S/N =3)分别为0.75、0.81、0.66、0.68、0.74、0.86 mg/L.方法用于化妆品样品测定,加标回收率在93.5％～105％之间,RSD均小于4.3％(n=3).     

Micellar electrophoresis using ionic liquids

In this study, ionic liquid based cationic surfactants were evaluated as pseudo-stationary phases in micellar electrokinetic chromatography (MEKC). The aggregation behaviour of long-chain (C(12) and C(14)) alkylimidazolium ionic liquids in water and aqueous phosphate buffer was investigated by spectrophotometry. The critical micelle concentrations of these salts were determined and compared to those of tetradecyl- and dodecyltrimethylammonium chloride, salts commonly used in capillary electrophoresis. The practical utilization of a new type of surfactant in MEKC was evaluated by introducing an ionic liquid into the running aqueous buffer to separate neutral analytes-methylresorcinol isomers and benzene derivatives.     

Enantioselectivity of alcohol-modified polymeric surfactants in micellar electrokinetic chromatography

A novel method of modifying sodium undecanoyl-L-leucinate (SUL) micelles employed in chiral separation of analytes in micellar electrokinetic chromatography (MEKC) to enhance selectivity toward specific analytes is discussed. The current study aimed at modifying the SUL micelles by introducing different alcohols into the mono-SUL micelles. The micellar solutions were then polymerized in the presence of alcohols followed by postpolymerization extraction of the alcohols to yield alcohol-free polymeric surfactants (poly-L-SUL). The effects of hexanol (C(6)OH) and undecylenyl alcohol (C(11)OH) on micellar properties of this surfactant were investigated by use of surface tensiometry, fluorescence spectroscopy, pulsed field gradient-nuclear magnetic resonance (PFG-NMR), and MEKC. The surface tension and PFG-NMR studies indicated an increase in the critical micelle concentration (cmc) and micellar size upon increasing the alcohol concentration. Fluorescence measurements suggested that alcohols induce closely packed micellar structures. Coumarinic and benzoin derivatives, as well as (+/-)-1, 1'-binaphthyl-2,2'-dihydrogen phosphate (BNP) were used as test analytes for MEKC experiments. Examination of MEKC data showed remarkable resolutions and capacity factors of coumarinic derivatives obtained with modified poly-L-SUL as compared to the unmodified poly-L-SUL. Evaluation of fluorescence, PFG-NMR, and MEKC data suggest a strong correlation between the polarity and hydrodynamic radii of alcohol-modified micelles and the resolution of the test analytes.     

A comparison of ionic liquids to molecular organic solvents as additives for chiral separations in micellar electrokinetic chromatography

In this study, we report the effects of adding ionic liquids (ILs), as compared to adding conventional molecular organic solvents (MOSs), to aqueous buffer solutions containing molecular micelles in the separation of chiral analyte mixtures in micellar EKC (MEKC). The molecular micelle used in this study was polysodium oleyl-L-leucylvalinate (poly-L-SOLV). The ILs were 1-alkyl-3-methylimidazolium tetrafluoroborate, where the alkyl group was ethyl, butyl, hexyl, or octyl. These ILs were chosen due to their hydrophobicity, good solvating, and electrolyte properties. Thus, it was expected that these ILs would have favorable interactions with chiral analytes and not adversely affect the background current. Common CE buffers, mixed with a molecular micelle, and an IL or a MOS, were used for these chiral separations. The buffers containing an IL in the concentration range of 0.02-0.1 v/v were found to support a reasonable current when an electric field strength of 500 V/cm was applied across the capillary. However, a current break down was observed for the buffers containing more than 60% v/v MOS on application of the above-mentioned electric field. The chiral resolution and selectivity of the analytes were dependent on the concentration and type of IL or MOS used.     

Insight into the mechanism of transient trapping in micellar electrokinetic chromatography

Transient trapping is a new mechanism of on-line sample concentration and separation that has recently been presented. It involves the injection of a short length of micellar solution in front of the sample, making it similar to sweeping in partial-filling MEKC. Here, we examine the mechanism of transient trapping by the use of computer simulations and compare it to sweeping in MEKC for the two analytes, sulforhodamine B and 101. The simulation results confirm the mechanism for concentration and separation originally proposed. The mechanism for concentration is similar to sweeping since the analytes are picked and accumulated by the micelles that penetrate the sample zone. The mechanism for separation is however quite unique since the concentrated analytes are trapped for a few seconds on the sample/micelle boundary before they are released as the concentration of micelle is reduced as it undergoes electromigration dispersion and the analytes separate down a micelle gradient. Simulation results suggested that a significant contribution of band broadening arises from the micelle gradient, with shallower gradients resulting in broader peaks. However, this is offset by an increase in selectivity, such that resolution was enhanced even though the peaks are broader. Transient trapping analysis with similar resolution to those obtained by sweeping MEKC could be achieved in 1/10 of the time and 1/4 of the capillary length, which results in a 2-3 times increase in sensitivity.     

Determination of polyphenol components in herbal medicines by micellar electrokinetic capillary chromatography with Tween 20

A simple and convenient method of micellar electrokinetic capillary chromatography (MEKC) using polyoxyethylene sorbitan monolaurate (Tween 20) to form single micelle and methanol as a buffer additive was introduced for the simultaneous determination of five polyphenols, including scopoletin, rutin, esculetin, chlorogenic acid and caffeic acid. A running buffer solution of pH 9.3, 20 mmol/L sodium tetraborate containing 64 mmol/L Tween 20 and 9% (v/v) methanol was adopted in the separation. Because rutin and esculetin were difficult to be separated by capillary zone electrophoresis (CZE) and SDS-based MEKC, Tween 20-based MEKC was adopted and the polyphenols were separated satisfactorily. The proposed method was used to determine the polyphenol components in the herbal medicine of Cortex fraxini. The separation mechanism of Tween 20-based MEKC for the polyphenols was discussed preliminarily.     

Micellar electrokinetic chromatography for high‐performance analytical separation

Capillary electrophoresis (CE) is a relatively new method of analytical separation having the advantages of high separation efficiency, requirement of a small sample amount, low operating cost, and fast separation time. CE is a separation method where the analyte migrates under an electric field due to a charge on the analyte. Hence, CE was unable to separate neutral analytes until the advent of micellar electrokinetic chromatography (MEKC). MEKC is performed with an addition of ionic micelles to an electrophoretic medium, where a portion of the analyte is incorporated into the micelle and has an apparent charge, which can be subject to electrophoretic separation. The migration velocity of the neutral analyte in MEKC depends on what portion of the analyte is incorporated into the micelle. Thus, the separation principle of MEKC is similar to that of chromatography, although the micelle corresponding to the stationary phase in chromatography is not stationary inside the capillary. The fundamental characteristics and theoretical treatments of the behavior of the analyte in MEKC were studied extensively by the author's group. MEKC has been established as one of the most popular separation modes in CE. This review describes how MEKC was developed and how it is useful as a method of analytical separation. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 291–301; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20156     

Solute-solvent interactions in micellar electrokinetic chromatography: IV. Characterization of electroosmotic flow and micellar markers

A wide study of the compounds and procedures mostly used to determine the electroosmotic flow (EOF) and micelle elution times has been done in seven different micellar electrokinetic chromatography (MEKC) systems. These systems are formed from mixtures of an aqueous buffer with the surfactants sodium dodecyl sulfate, lithium dodecyl sulfate, lithium perfluorooctane sulfonate, sodium cholate, sodium deoxycholate, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide. The solvation parameter model has been used to evaluate the usefulness of the compounds studied as EOF or micellar markers in each of the seven MEKC systems. It is demonstrated that methanol, acetonitrile and formamide are the best EOF markers, and that dodecanophenone is the best micellar marker.     

Macromolecular surfactant as a pseudo-stationary phase in micellar electrokinetic capillary chromatography

We examined polymers of sodium 11-acrylamidoundecanoate [poly(Na 11-AAU)] with a very high molecular mass (>10(6)) for their potential use as a pseudo-stationary phase in micellar electrokinetic capillary chromatography (MEKC). Size-exclusion chromatography and capillary electrophoresis studies reveal that the polymers are highly charged, and have a densely packed chain structure. For aromatic compounds, the polymeric surfactant showed significantly different selectivity than sodium dodecyl sulfate (SDS). It was suggested that one molecule of poly(Na 11-AAU) forms one micelle. The structural stability of this pseudo-stationary phase permitted its use with relatively high percentages of organic modifiers in the buffer medium, allowing the separation of highly hydrophobic compounds which are difficult to analyze by conventional MEKC with SDS.     

Micelle to trapping solution stacking in micellar electrokinetic chromatography

An analytical strategy micelle to trapping solution stacking (MSS) was developed in acidic buffer in micellar electrokinetic chromatography (MEKC). The stacking mechanism is based on the transport, release, capturing of molecules bound to micelle carriers that are made to collapse into trapping solution (TS) to serve as the medium to contain and stacking the analytes. Tetrandrine and fangchinoline were selected as model mixture using sodium dodecyl sulfate (SDS) micelles as carrier to demonstrate this stacking method. The experiments by MSS-MEKC were carried out and further compared with those by normal MEKC. The results reveal that 113–123-fold improvements in the detection sensitivity was obtained for the analytes, and separation and determination of tetrandrine and fangchinoline in Stephaniae tetrandrae S. Moore and Fengtongan capsules were finished under optimum conditions using the sample matrix containing 8.0 mM SDS and TS containing 50 mM H₃PO₄–55% (v/v) ethanol.     

Towards a general approach for the impurity profiling of drugs by micellar electrokinetic chromatography

A general micellar electrokinetic chromatographic (MEKC) strategy for the impurity profiling of drugs was developed involving a sodium dodecyl sulfate (SDS) and a cetyltrimethylammonium bromide (CTAB) MEKC system. With this combination, in principle, each sample component passes the detector in at least one of the two MEKC systems provided that separation buffers of the same pH are used in both systems. In order to select the proper MEKC systems, the electroosmotic flow (EOF) and micelle migration time (t(mc)) were determined for separation buffers of several pH values, containing various amounts of surfactant and organic modifier. The selectivity of the MEKC systems was studied using a mixture of compounds with a wide range of physico-chemical properties. The final selection of two adequate MEKC systems for this approach was based on the requirements that the t(mc) (i.e., analysis time) of both systems was below 20 min and that the t(mc)/t(eof) ratio was above 3 or 2 for the SDS and CTAB system, respectively. Furthermore, the systems should provide high efficiency, exhibit differences in selectivity and use moderate concentrations of modifier and surfactant, so that, if needed, further optimization is possible. The selected MEKC systems contained 60 mM SDS or 10 mM CTAB, respectively, in a phosphate buffer (pH 7.5) with 10% acetonitrile. Some test compounds with extreme mobilities were used to demonstrate the suitability of the MEKC approach to detect each component of a sample. The potential of the proposed MEKC combination for impurity profiling was demonstrated by the analysis of fluvoxamine with several impurities at the 0.1% level.