高效毛细管电泳电导检测器的研制

研制了一种毛细管电泳电导检测器。采用激光烧蚀毛细管涂层、HF腐蚀和阴离子交换膜封堵制作在柱导电接口连接电泳毛细管和电导池,高压电场被有效隔离,以铂丝为工作电极实现柱后电导检测,在内径为50μm毛细管上分离检测了几种氨酸和金属离子,结果表明该系统性能优良。     

常规离子色谱系统-电容耦合非接触式电导检测器的构建

通过考察电极长度及电极间距、检测管管径及材质、激励信号频率、电压和波形等参数对信噪比的影响,研制了一种适用于常规型离子色谱系统的电容耦合非接触式电导检测器（C⁴D）。在抑制模式下,该检测器对常见无机阴离子（F^-、Cl^-、NO₂^-、Br^-、NO₃^-和SO₄^2-）的检出限（信噪比=3）为0.02~0.08 μmol/L;峰面积的相对标准偏差<1.8%（n=6）;在0.1~10 μmol/L范围内上述6种无机阴离子线性关系良好,相关系数（R²）>0.999。自制C⁴D的主要性能参数与商品化接触式电导检测器相当。该检测器具有结构简单、成本低廉、无电极污染等优点,有利于拓展离子色谱的应用范围。     

毛细管电泳非接触式电导检测快速分离和测定氨基糖苷类抗生素

用带非接触式电导检测器的毛细管电泳法(CE)分离并测定了3种氨基糖苷类抗生素,即缺少较强紫外吸收发色团或荧光发射基团的庆大霉素(GE)、卡那霉素(KA)和链霉素(ST)。对影响CE分析的因素进行了研究,并确定以下几项优化的参数:①电泳介质:选用35mmol·L-12-(N-吗啉)乙磺酸溶液和15mmol·L-1组氨酸溶液组成的缓冲体系;②分离电压:17kV;③激发电压:60V;④激发频率:600kHz;⑤进样时间:5s。在所选最佳条件下,上述3种抗生素可在10min内达到完全分离。上述3种抗生素的质量浓度在一定范围内与其相应的峰面积呈线性关系,其检出限(3S/N)依次为0.2,0.4,0.2mg·L-1。     

毛细管电泳高频电导检测器的研制

设计了一种新的毛细管电泳检测器.根据高频电导滴定原理,将电导电极做成两个金属圆筒套于分离毛细管外,并向两个电极施加高频电压.经毛细管分离后的组分流过两个电极之间时,高频电流发生变化,得到毛细管电泳图.该检测器具有应用范围广、操作简便及重现性好等优点,已初步应用于混合无机离子的测定.     

毛细管电泳-非接触式电导法直接测定偏硅酸

采用毛细管电泳-电容耦合非接触式电导检测(CE-C<'4>D),以2.4mmol/L KOH+1.6mmol/L K<,2>HPO<,4>+0.4 mmol/L 十六烷基溴化铵(CTMAB)为电泳运行液,融硅石英毛细管(45cm×50μm,有效长度40 cm),负高压分离(-15 kV),偏硅酸可在6.0 min内实现...     

毛细管电泳/非接触式电导法分离检测氧氟沙星对映体

采用毛细管电泳-电容耦合非接触式电导(CE-C4D),以20 mmol/L HAc + 6 mmol/L NaAc+12 mg/L羟丙基甲基纤维素(HPMC)+35 mmol/L羟丙基-β-环糊精(HP-β-CD)为电泳运行液,在熔融石英毛细管柱(45 cm×50 μm i.d.,有效长度 40 cm)中,正高压分离,手性药物氧氟沙星对映体获得良好的基线分离,线性检测范围为0.8～40 mg/L,检出限为0.3 mg/L.考察了电泳运行液组成、二元手性选择剂(HP-β-CD和HPMC)的浓度、进样方式和样品基质等对灵敏度和分离度的影响.本方法应用于市售外消旋和左旋氧氟沙星片剂中对映体的分离测定.     

场放大进样-毛细管电泳非接触式电导快速检测蔬菜中草酸

采用场放大进样-毛细管电泳非接触式电导,建立了分离检测蔬菜中水溶性草酸的方法。以25 mmol/L乙酸溶液为电泳运行液,未涂层石英毛细管,负高压分离,电动进样-11 kV×10 s,草酸可在5 min内获得良好分离和灵敏检测,检出限为6μg/L,定量限为20μg/L。日内和日间精度的相对标准偏差(RSD)≤5%。蔬菜样品中共存的常见无机阴离子和有机基质不干扰草酸的测定,样品无需复杂的前处理就可直接进样分析。该方法可用于蔬菜中水溶性草酸含量的检测。     

耦联式安培-电导检测器的研制及其在CE中的应用

毛细管电泳(CE)检测器的研究是一个具有挑战性的课题.目前已发展的一些检测方法有光学、电化学、质谱的和放射同位素等.     

毛细管电泳/非接触式电导法分离检测手性药物氨氯地平对映体

采用毛细管电泳/电容耦合非接触式电导( CE/C4 D),以18 mmol/L柠檬酸+6 mmol/L氨水+12 mg/L羟丙基甲基纤维素(HPMC)+ 35 mmol/L羟丙基-β-环糊精(HP-β-CD)为电泳运行液,熔融石英毛细管(50μm i.d.×45 cm,leff=40 cm),正高压(+15 kV)分离...     

毛细管电泳非接触电导检测技术的新发展

毛细管电泳非接触电导检测(CE-CCD)是近年来发展迅速的一种检测技术。本文介绍了非接触式电导检测(CCD)的发展概况,着重阐述了CCD的原理、组成及应用情况。     

扑尔敏对映体的毛细管电泳-方波安培分离检测

报道了以未涂层融硅石英毛细管(50 cm×75 μm)为分离柱,5 mmol/L NaOH+10 mmol/L Citric acid +3 mmol/L H3BO3+10 mmol/L β-CD (pH 3.5) 为电泳介质,分离电压12 kV,检测电压0.80 V,建立了朴尔敏对映体拆分的高效毛细管电泳-方波安培检测方法.对缓冲溶液的种类、浓度、pH、分离电压对拆分效果的影响进行了讨论,并对拆分机理进行了探讨.     

Fundamental aspects of contactless conductivity detection for capillary electrophoresis. Part II: Signal-to-noise ratio and stray capacitance

The signal-to-noise ratio of a contactless conductivity detector for capillary electrophoresis was examined for different cell arrangements and operating parameters. The best signal-to-noise ratios, and hence the best detection limits, are obtained for frequencies which give highest sensitivity. Comparative experiments for three different excitation voltages (20, 100, and 200 V(pp)) showed that the best signal-to-noise ratios were achieved for the highest excitation voltage of 200 V(pp). Low conductivity of the background electrolyte solution is mandatory to obtain lowest noise levels, and also the improvement on applying high excitation voltages was best for the electrolyte solution with lowest conductivity. The diameter of the electrodes was found to have only a negligible effect, so that a tight fitting of the electrodes to the external diameter of the capillary is not necessary. A cell without shielding between the two electrodes showed significant direct coupling (stray capacitance) and lower signal-to-noise ratios for all experimental conditions used. A serious distortion of the peak shapes was also observed for this cell arrangement.     

Determination of PCR products by CE with contactless conductivity detection

The use of CE with contactless conductivity detection for the determination of PCR products is demonstrated for the first time. The separation of specific length PCR products according to their size could be achieved using 5% PVP as a sieving medium in a separation buffer consisting of 20 mM Tris and 20 mM 2‐(cyclohexylamino)ethansulphonic acid (pH 8.5). A fused silica capillary of 60 cm length and 50 μm id and an applied separation voltage of –15 kV were employed and separations could be completed within 20–50 min. PCR amplified DNA fragments of different sizes obtained from different bacterial plasmid templates as well as a fragment from genomic DNA of genetically modified soybeans could be successfully identified.     

Evaluation of the detection of biomolecules in capillary electrophoresis by contactless conductivity measurement

The sensitivity of contactless conductivity detection to amino acids, peptides and proteins in CE was studied for BGE solutions of different pH values. The LOD and analytical characteristics were compared for acidic and basic conditions and better results were in most cases found for buffers of low pH values. Linear dynamic ranges varied between two orders of magnitude for amino acids and peptides and three orders of magnitude for larger proteins. The concentration detection limits were found to be between 1.2 and 7.5 microM for the amino acids tested and for the larger molecules they varied between 2.6 microM for leucine enkephalin and 0.2 microM for HSA when using a buffer at pH 2.1.     

Separation of enantiomers in capillary electrophoresis with contactless conductivity detection

Contactless conductivity detection is successfully demonstrated for the enantiomeric separation of basic drugs and amino acids in capillary electrophoresis (CE). Derivatization of the compounds or the addition of a visualization agent as for indirect optical detection schemes were not needed. Non-charged chiral selectors were employed, hydroxypropylated cyclodextrin (CD) for the more lipophilic basic drugs and 18-crown-6-tetracarboxylic acid (18C6H4) for the amino acids. Acidic buffer solutions based on lactic or citric acid were used. The detection limits were determined as 0.3 microM for pseudoephedrine as an example of a basic drug and were in the range from 2.5 to 20 microM for the amino acids.     

A review of the recent achievements in capacitively coupled contactless conductivity detection

Capacitively coupled contactless conductivity detection (C⁴D) in the axial electrode configuration was introduced in 1998 as a quantification method for capillary electrophoresis. Its universality allows the detection of small inorganic ions as well as organic and biochemical species. Due to its robustness, minimal maintenance demands and low cost the popularity of this detector has been steadily growing. Applications have recently also been extended to other analytical methods such as ion chromatography, high-performance liquid chromatography and flow-injection analysis. C⁴D has also found use for detection on electrophoresis based lab-on-chip devices. Theoretical aspects of C⁴D in both the capillary and microchip electrophoresis format have been comprehensively investigated. Commercial devices are now available and the method can be considered a mature detection technique. In this article, the achievements in C⁴D for the time period between September 2004 and August 2007 are reviewed.     

Determination of different classes of amines with capillary zone electrophoresis and contactless conductivity detection

The use of contactless conductivity detection for the determination of different organic amines in CE was successfully demonstrated. Aliphatic non UV-absorbing species could be determined along absorbing compounds by measuring the conductivity of their protonated forms. The species tested included short-chained aliphatic primary, secondary and tertiary amines, branched aliphatic amines, diamines, hydroxyl-substituted amines as well as species incorporating aromatic and non-aromatic cyclic moieties. Highest sensitivity was obtained with BGE solutions containing solely acetic acid. A concentration of 0.5 M at a pH value of 2.5 was used. Detection limits were in the order of 1 microM. Complete separation of cis- and trans-1,2-diaminocyclohexane could be achieved by adding 18-crown-6 as modifier to the electrolyte solution.     

Analysis of amino acids in cell culture supernatant using capillary electrophoresis with contactless conductivity detection

CE-C⁴D methods for the analysis of amino acids (AAs) are presented. Combining the results from two methods with acetic acid and cyclodextrin-based BGEs, 20 proteinogenic AAs could be analyzed using CE. CE-C⁴D was also, for the first time, applied to analyze free AAs in samples of mammalian cell culture supernatant. After dilution as only sample preparation, combining the results of the two CE methods allowed monitoring the concentration changes of 17 AAs in samples taken during the cultivation of CHO cells.     

Capillary electrophoresis with contactless conductivity detection for uric acid determination in biological fluids

The suitability of capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C⁴D) for the direct determination of uric acid in human plasma and urine was investigated. It was found that a careful optimization of the buffer composition and pH was necessary to achieve selective determination in the complex sample matrices. An electrolyte solution consisting of 10 mM 2-morpholinoethanesulfonic acid (MES), 10 mM histidine and 0.1 mM hexadecyltrimethylammonium bromide (CTAB), pH 6.0, was finally found suitable for use as running buffer for both sample matrices. The limit of detection (3 S/N) was determined as 3.3 μM. The linearity of the response was tested for the range between 10 and 500 μM and a correlation coefficient of 0.9996 was obtained. Intra- and inter-day variabilities were <10%. Quantitative analysis of urine and plasma samples showed a good correlation with the routine enzymatic method currently used at the University Hospital of Basel.     

Fast electrophoresis in conventional capillaries by employing a rapid injection device and contactless conductivity detection

A purpose-made set-up featuring an automated fast injector allowed the easy optimization of the injected amount and the adjustment of the separation length of conventional capillaries from a minimum of 5 cm upward. It was found that a compromise in capillary length for separation efficiency and analysis time also has to take into account the injected amount, which in turn affects the sensitivity and hence the detection limit. The versatility of the system was demonstrated by the analysis of the major cations and anions in natural water samples in less than 1 min, the concurrent determination of a mixture of amino acids and carbohydrates in 160 s, and of three active ingredients in a pharmaceutical preparation in 40 s. Plate numbers were typically around 50,000 and detection limits down to 1 M could be achieved.