毛细管电泳分离I^—和IO3^—中的电渗流的控制与调节

毛细管电泳分离是基于带电粒子在电场下的电动现象，当电场加到带电粒子所处的介质上时，存在电泳和电渗两种电动现象，其中电泳与带电粒子的大小、电荷和形状有关，而电渗与毛细管的表面及电泳介质的组成有关．由于电渗流能显著地影响分析时间和分离效率，因此，控制电渗流在毛细管电泳分离中是一个重要的环节［‘·‘j．此外，调节PH值、离子强度和缓冲液的粘度也是常用的控制电渗流的方法［’j．Ewing［‘与1入一个附加电场来控制电渗流．在缓冲液中加入足够浓度的阳离子表面活性剂将改变电渗流的方向．与通常的电渗流相比，人们对反向…     

在柱双重富集毛细管电泳法测定卷烟样品中的无机阴离子

采用在柱阴离子选择性耗尽进样(ASEI)-碱堆积(BS)双重富集毛细管电泳法测定了卷烟样品中无机阴离子。毛细管先充满含0.4 mmol/L十四烷基三甲基溴化铵(TTAB)的三羟甲基氨基甲烷(Tris)缓冲液抑制电渗流;再以高差法引入水塞,吸附于毛细管壁的TTAB溶解到水中,使该段毛细管的zeta电势变负;电泳电源用负高压,电动进样时样品池中阴离子快速迁移并堆积在毛细管内缓冲液和水塞界面上,同时流向进样端的电渗流将水塞排出毛细管;接着电动注入NaOH溶液,快速迁移的OH-与来自缓冲液的Tris+形成低电导样品区,可进一步堆积样品带,还可使电动进样的时间延长。同常规电动进样相比,该双重富集法可达到(0.8~1.3)×105的富集倍数。用本方法测定了卷烟中6种无机阴离子,检出限低于6.2 ng/L。     

毛细管电泳-间接紫外检测法分离和测定食品中的有机酸

有机酸毛细管电泳（CE）分析是90年代初首先被报道的[1],近年来有了较大的发展[2]．采用CE法可进行不同基质样品如食品、饮料、尿液等样品中多种有机酸的同时分析[1,3,4]．该法采用CE的阴离子分离模式,在电解质溶液中加入电渗流改性剂,使电渗流方向逆向,从而与阴离子的电泳方向一致,以缩短分析时间．常见有机酸在200um以上大多无紫外吸收,一般采用间接紫外检测方法[1,3],也可采用低波长紫外检测[4]．低分子量阴离子的CE研究报道不多[5,6],有机酸的CE分离系统研究尚未见报道．本文系统地研究了毛细管电泳-间接紫外检测法分析…     

乙酸和一氯乙酸电离常数的高效毛细管区带电泳法测定

首次建立了测定一氯乙酸和乙酸的电离常数的高效毛细管区带电泳新方法.该方法利用中性标记物和电流突跃两种方法来标记电渗流,通过测定乙酸和一氯乙酸在一定pH的缓冲溶液中的电泳淌度,结合数据回归分析拟合,求得乙酸和一氯乙酸的电离常数;所得数据和文献报道值较为接近.总体而言,毛细管区带电泳法可简单、快速、可靠地用于测定待测化合物的电离常数.     

负载型催化剂制备的聚丙烯等规度分布

负载型Ziesler－Natta催化剂中存在许多活性中心［'3，为了解其本质，需对其各自产生的聚合物进行分离，以往采用的溶剂抽提法［'－'j只能将聚合物大致分级．最近，升温淋洗分级法（TREF）已被运用于聚丙烯的分级卜，'，其原理是根据聚合物的结晶度分级D'，影响聚丙烯结晶性的主要因素是等规度，而分子量到达一定程度后其影响较小，故通过TREF分级可得到聚丙烯的等规度分布．TREF法的淋洗温度可控，故分级效果较好．该法在分级前需对样品进行等温结晶处理，以消除抽提法由于样品未必充分结晶而带来的误差．本文用TREF法对不同催化…     

新型毛细管等电聚焦驱动方法的建立及其应用

毛细管等电聚焦(CIEF)在生物分离分析领域中的发展迅速．CIEF可分为两步法聚焦和一步法聚焦．电渗流(EOF)可作为一种新的驱动力．Rassi等根据串连体系中电渗流速率将被平均化的原理,将未涂层毛细管与聚乙二醇涂层的毛细管通过聚四氟乙烯管耦合起来,成功地利用毛细管区带电泳快速分离蛋白．此外,利用电渗流输液原理设计的电渗泵还可用作流动注射和微柱液相色谱的驱动系统。     

不同价态铬离子的毛细管电泳分离与测定

１引言由于元素的不同价态、不同存在形态具有不同的物理、化学性质与生理活性。如Ｃｒ（Ⅲ）是人体必需的元素，而Ｃｒ（Ⅵ）则是有害的。因此，离子的价态分析具有十分重要的意义。由于毛细管电泳可实现阴阳离子的同时分析，与离子色谱相比，具有简单、快速的特点。本文采用样品与ＥＤＴＡ络合的办法，用毛细管电泳在ＣＨ３ＣＯＯＮａ－ＣＨ３ＣＯＯＨ体系中（含电渗流改性剂和络合剂），对ＣｒＯ４２－、Ｃｒ３＋的分离测定进行了研究。用直接紫外法检测在５．５ｍｉｎ内可完成两种价态铬离子的测定，特别适于电镀废液或其它水质的分析。…     

反相毛细管电色谱中两种电渗流测定方法的比较

在毛细管电色谱中电渗流的测定方法有许多种,常用的是示踪剂法。本文将硫脲示踪剂法和迭代分析法测定的电渗流结果加以对比分析,结果表明:在不同有机调节剂体积分数、不同电压、不同电解质浓度下,虽然用两种方法测得的电渗流随诸因素的变化规律符合电渗流变化的一般规律,但强极性硫脲分子存在电迁移现象,使测得的电渗流较真实值有所偏离。偏离的大小随有机调节剂体积分数、电解质浓度等实验条件变化。     

微胶囊化颜料粒子表面形貌的模式识别及量化表征

材料粒子的微胶囊化可提高材料的某些耐性［'j．群青颜料色泽鲜艳，但不耐酸，对群g粒子进行微胶囊化可改善其耐酸性．但由于相应粒子表面形貌不同，难以辩别与描述．本方使民计算机图像处理［'屿模式识别技术［'j，并用表面分形维数量化表征粒子的表面形貌［'j．1实验部分以群青粒子为芯材、以Na。SIO。与NH。CI水解产物硅胶为膜材，进行粒子的微胶囊化．将改变乳化剂浓度、搅拌速率两系列微胶囊化样品及原样采用JFY－ABI型测色计进行耐酸性色差（凸E）测试．粒子的表面形貌在X－650型扫描电子显微镜（配图像分析仪）下，经过数S化…     

葫［7］环联脲作为毛细管电泳分离介质的研究

以葫［7］环联脲(CB［7］)作为毛细管电泳添加剂,成功地分离了6种硝基苯类化合物。考察了pH值对电渗流的影响,初步评价了其基本的电泳性能,结果表明在所考察的pH值范围内(pH 2~6.5),葫［7］环联脲是质子化的,且吸附到毛细管内壁上,这使得毛细管内壁带上正电荷,电渗流反向;初步考察了葫［7］环联脲的浓度对分离的影响,证明了用葫［7］环联脲作为添加剂可完全分离对硝基乙苯、对硝基甲苯、对氯硝基苯、间二硝基苯、2,4-二硝基氯苯和硝基苯这6种物质,最佳的缓冲液为10 mmol/L Na2HPO4（用盐     

A New Method to Measure Electroosmotic Flow Mobility of Capillary Electrophoresis by Abrupt Change of Current De‐noising via Wavelet Transform

The electroosmotic flow mobility has been measured by the combination of monitoring the change in electric current during electrophoretic run and operating the wavelet transform. Once the sample solvent zone with different ionic strength from background electrolyte migrated from the capillary, a sudden change in current could be observed from the electric current record of time history. The exact time (in the middle of abrupt range) corresponding to the abrupt change in current was determined by wavelet transform. This work showed that the electroosmotic flow mobility determined by the proposed method was in a good agreement with the neutral marker method commonly used.     

The application of spline wavelet transform to the determination of electroosmotic mobility in capillary electrophoresis

The rule of current change was studied during capillary electrophoresis (CE) separation process while the conductivity of the sample solution was different from that of the buffer. Using a quadratic spline wavelet of compact support, the wavelet transforms (WTs) of capillary electrophoretic currents were performed. The time corresponding to the maximum of WT coefficients was chosen as the time of current inflection to calculate electroosmotic mobility. The proposed method was suitable for different CE modes, including capillary zone electrophoresis, nonaqueous CE and micellar electrokinetic chromatography. Compared with the neutral marker method, the relative errors of the developed method for the determination of electroosmotic mobility were all below 2.5%.     

Chitosan as cationic polyelectrolyte for the modification of electroosmotic flow and its utilization for the separation of inorganic anions by capillary zone electrophoresis.

Cationic polyelectrolyte of chitosan was used for the reversal of electroosmotic flow in capillary zone electrophoresis. The chitosan was dissolved in acetic acid solution, and stable electroosmotic flow was obtained at the chitosan concentrations between 50 and 300 microg/mL. Separation of inorganic anions was carried out using the dynamically coated capillary by capillary zone electrophoresis. Nine kinds of anions were separated and detected with the capillary. The electrophoretic mobility of the analyte anions decreased with increasing concentrations of chitosan in the migrating solution through ion-ion interaction, but the migration order of the analyte anions was not changed in the concentration range of the chitosan examined. The signal shape for the analyte anions was developed by using field-enhanced sample stacking with 10 mM sodium sulfate.     

Mobilization of electroosmotic flow markers in capillary zone electrophoresis

UV-absorbing neutral substances are commonly used as markers of mean electroosmotic flow in capillary electrophoresis for their zero electrophoretic mobility in an electric field. However, some of these markers can interact with background electrolyte components and migrate at a different velocity than the electroosmotic flow. Thus, we tested 11 markers primarily varying in their degree of methylation and type of central atom in combination with five background electrolyte cations differing in their ionic radii and surface charge density, measuring the relative electrophoretic mobility using thiourea as a reference marker. Our results from this set of experiments showed some general trends in the mobilization of the markers based on the effects of marker structure and type of background electrolyte cation on the relative electrophoretic mobility. As an example, the effects of an inadequate choice of marker on analyte identification were illustrated in the electrophoretic separation of glucosinolates. Therefore, our findings may help electrophoretists appropriately select electroosmotic flow markers for various electrophoretic systems.     

On the pH hysteresis of electroosmotic mobility with capillary zone electrophoresis in silica capillary

Summary A porous gel model of silica-solution interface was proposed to explain the pH hysteresis effect on the electroosmotic mobility with capillary zone electrophoresis in silica capillaries. It is speculated that, under acidic preconditionings of the capillaries, a porous gel layer is formed at the silica-solution interface, and the magnitudes of potential and electroosmotic mobility are then reduced due to the penetration of electrolyte counterions to the gel layer. On the other hand, under basic preconditionings, a fresh silica surfaces is created by dissolution of silica in alkaline conditions, and this would result in higher values of potential and electroosmotic mobility. The Guoy-Chapman-Stern-Grahame model was employed to simulate the pH-dependence of electroosmotic mobility for the silica capillaries with a gelling surface and with a fresh surface. The predicted data were compared with the experimental results and shown to support the explanation.     

Continuous concentration of bacteria in a microfluidic flow cell using electrokinetic techniques

A novel method for the concentration of bacterial solutions is presented that implements electrokinetic techniques, zone electrophoresis (ZE) and isoelectric focusing (IEF), in a microfluidic device. The method requires low power (< 3e-5 W) and can be performed continuously on a flowing stream. The device consists of two palladium electrodes held in a flow cell constructed from layers of polymeric film held together by a pressure-sensitive adhesive. Both ZE and IEF are performed with carrier-free solutions in devices in which the electrodes are in intimate contact with the sample fluid. IEF experiments were performed using natural pH gradients; no carrier ampholyte solution was required. Experiments performed in buffer alone resulted in significant electroosmotic flow. Pretreatment of the sample chamber with bleach followed by a concentrated solution of cationic detergent effectively suppressed electroosmotic flow.     

Peak compression effects in capillary electrochromatography of basic drug substances using a strong cation-exchanger

Peak compression effects in capillary electrochromatography of basic drug substances using a strong cation-exchanger have been studied. Extremely narrow peaks with apparent efficiencies of several million plates per meter could be obtained when the composition of the sample zone differed from that of the mobile phase. The increased efficiencies were predominately observed when the analyte had an elution time similar to that of the electroosmotic flow marker. Peak compression was found to be reproducible and could be obtained for all investigated basic drug substances by altering the composition of the mobile phase in such a way that the analyte co-eluted with the sample zone. An explanation of the observed phenomena is proposed. A sample zone differing in composition from the mobile phase will disturb the equilibrium between the stationary and mobile phase. The elution rate of an analyte will consequently be different when residing inside the sample zone. If the analyte migrates through the sample zone at a higher speed than the rest of the mobile phase and is strongly retained after passing through a boundary in the sample zone, a continuous stacking can be obtained trapping the analyte as a very narrow band.     

Poly(vinyl alcohol)-coated microfluidic devices for high-performance microchip electrophoresis

The channels of microfluidic glass chips have been coated with poly(vinyl alcohol) (PVA). Applied for microchip electrophoresis, the coated devices exhibited a suppressed electroosmotic flow and improved separation performance. The superior performance of PVA-coated channels could be demonstrated by electrophoretic separations of labeled amines and by video microscopy. While a distorted sample zone is injected using uncoated channels the application of PVA-coated channels results in an improved shape of the sample zone with less band broadening. Applying PVA-coated microchips for the separation of amines labeled with Alexa Fluor 350 even sub-second separations, utilizing a separation length of only 650 microm, could be obtained, while this was not possible using uncoated devices. By using PVA-coated devices rather than an uncoated chip a threefold increase in separation efficiencies could be observed. As the electroosmotic flow (EOF) was suppressed, the anionic compounds were detected at the anode whereas the dominant EOF in uncoated devices resulted in an effective mobility to the cathode. Besides improved separation performance another important feature of the PVA-coated channels was the suppressed adsorption of fluorescent compounds in repetitive runs which results in an improved robustness and detection sensitivity. Applying PVA-coated channels, rinsing or etching steps could be omitted while this was necessary for a reliable operation of uncoated devices.     

Electrophoretic mobility measurements of fluorescent dyes using on-chip capillary electrophoresis

We present an experimental study of the effect of pH, ionic strength, and concentrations of the electroosmotic flow (EOF)-suppressing polymer polyvinylpyrrolidone (PVP) on the electrophoretic mobilities of commonly used fluorescent dyes (fluorescein, Rhodamine 6G, and Alexa Fluor 488). We performed on-chip capillary zone electrophoresis experiments to directly quantify the effective electrophoretic mobility. We use Rhodamine B as a fluorescent neutral marker (to quantify EOF) and CCD detection. We also report relevant acid dissociation constants and analyte diffusivities based on our absolute estimate (as per Nernst-Einstein diffusion). We perform well-controlled experiments in a pH range of 3-11 and ionic strengths ranging from 30 to 90 mM. We account for the influence of ionic strength on the electrophoretic transport of sample analytes through the Onsager and Fuoss theory extended for finite radii ions to obtain the absolute mobility of the fluorophores. Lastly, we briefly explore the effect of PVP on adsorption-desorption dynamics of all three analytes, with particular attention to cationic R6G.     

Selection of migration parameters for a highly reliable assignment of bands of isoforms of erythropoietin separated by capillary electrophoresis

Capillary zone electrophoresis of samples of recombinant human erythropoietin is performed. An in-house computer program is developed to compare the reliability of different migration parameters to assign the close migration bands of isoforms of erythropoietin. The migration time relative to the electroosmotic flow marker and the effective electrophoretic mobility are selected as the most accurate parameters. Percentages of correct assignment of bands higher than 99% are obtained with these parameters even when changes in operational factors are introduced. The chosen parameters have been applied to assign bands of isoforms in commercial samples of alpha- and beta-epoetin. The same capillary electrophoresis method has been applied to separate bands of isoforms of an erythropoietin analogue, darbepoetin alpha, the novel erythropoiesis-stimulating protein.