Pressure-assisted capillary electrophoresis for cation separations using a sequential injection analysis manifold and contactless conductivity detection

Pressure assisted capillary electrophoresis in capillaries with internal diameters of 10 μm was found possible without significant penalty in terms of separation efficiency and sensitivity when using contactless conductivity detection. A sequential injection analysis manifold consisting of a syringe pump and valves was used to impose a hydrodynamic flow in the separation of some inorganic as well as organic cations. It is demonstrated that the approach may be used to optimize analysis time by superimposing a hydrodynamic flow parallel to the electrokinetic motion. It is also possible to improve the separation by using the forced flow to maintain the analytes in the capillary, and thus the separation field, for longer times. The use of the syringe pump allows flexible and precise control of the pressure, so that it is possible to impose pressure steps during the separation. The use of this was demonstrated for the speeding up of late peaks, or forcing repeated passage of the sample plug through the capillary in order to increase separation.     

Simultaneous determination of atenolol and amiloride in pharmaceutical preparations by capillary zone electrophoresis with capacitively coupled contactless conductivity detection

Capillary zone electrophoresis coupled with a capacitively coupled contactless conductivity detector (CE‐C⁴D) has been employed for the determination of atenolol and amiloride in pharmaceutical formulations. Acetic acid (150 mm ) was used as background electrolyte. The influence of several factors (detector excitation voltage and frequency, buffer concentration, applied voltage, capillary temperature and injection time) was studied. Non‐UV‐absorbing L‐valine was used as internal standard; the analytes were all separated in less than 7 min. The separation was carried out in normal polarity mode at 28°C, 25 kV and using hydrodynamic injection (25 s). The separation was effected in an uncoated fused‐silica capillary (75 μm, i.d. × 52 cm). The CE‐C⁴D method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 5–250 μg/mL for the studied analytes. The relative standard deviations of intra‐ and inter‐day migration times and corrected peak areas were less than 6.0%. The method showed good precision and accuracy and was successfully applied to the simultaneous determination of atenolol and amiloride in different pharmaceutical tablet formulations. Copyright © 2010 John Wiley & Sons, Ltd.     

多材料3D打印技术制作用于毛细管电泳的非接触电导/激光诱导荧光二合一检测池

利用多材料3D打印技术研制了用于毛细管电泳(CE)的二合一检测池,实现了电容耦合非接触电导(C4D)与共聚焦激光诱导荧光(LIF)两种检测方法在毛细管柱上同一位置同时检测.3D打印的检测池采用了导电的复合聚乳酸(PLA)材料制作C4 D的屏蔽层,采用普通的绝缘PLA材料支撑C4 D金属管电极并隔离屏蔽层.两根金属管电极...     

Determination of vitamin C and preservatives in beverages by conventional capillary electrophoresis and microchip electrophoresis with capacitively coupled contactless conductivity detection

The separation and detection of commonly used preservatives (benzoate, sorbate) and vitamin C by both conventional CE and microchip electrophoresis with capacitively coupled contactless conductivity detection is presented. The separation was optimized by adjusting the pH-value of the buffer and the use of hydroxypropyl-beta-CD (HP-beta-CD) and CTAB as additives. For conventional CE, optimal separation conditions were achieved in a histidine/tartrate buffer at pH 6.5, containing 0.025% HP-beta-CD and 0.1 mM CTAB. LOD ranged from 0.5 to 3 mg/L (S/N = 3) and the RSDs for migration time and peak area were less than 0.1 and 2%, respectively. A considerable reduction of analysis time can be accomplished by using microchip electrophoresis without significant loss in sensitivity under optimal separation conditions. A histidine/tartrate buffer at pH 6.5, incorporating 0.06% HP-beta-CD and 0.25 mM CTAB, gave detection limits ranging between 3 and 10 mg/L and satisfactory reproducibilities of < or =0.4% for the migration time and < or =3.5% for the peak area. The methods developed are useful for the quantitative determination of food additives in real samples such as soft drinks and vitamin C tablets.     

硫酸沙丁胺醇的毛细管电泳非接触电导法检测

建立了毛细管电泳-非接触电导检测分离测定硫酸沙丁胺醇的分析方法。分别考察了分离介质、背景电解质及其浓度和pH、分离电压、进样时间、激发电压、激发频率等因素对实验结果的影响。在优化的实验条件(以15 mmol/L乳酸水溶液(pH 2.7)为电泳介质,10 kV下电动进样3 s,分离电压为10 kV,激发电压为60 V,激发频率为120 kHz)下,硫酸沙丁胺醇的检出限(信噪比为3)为1.92 mg/L,在9.60～48.0 mg/L质量浓度范围内有良好的线性关系(r=0.995),迁移时间的相对标准偏差(RSD)为2.7%。将该方法用于硫酸沙丁胺醇片和硫酸沙丁胺醇气雾剂中的硫酸沙丁胺醇含量的测定,加标回收率为90%～113%,检测结果与药厂的标示值相符合,为硫酸沙丁胺醇的检测提供了一种简便、快速、高灵敏的方法。关键词: 毛细管电泳;非接触电导检测法;硫酸沙丁胺醇;硫酸沙丁胺醇片;硫酸沙丁胺醇气雾剂     

Contactless conductivity detection for screening myrosinase substrates by capillary electrophoresis

Myrosinase is a unique enzyme that catalyzes the hydrolysis of glucosinolates (GLS) to isothiocyanate (ITC), glucose and sulfate. Isothiocyanates display a diversified very interesting biological activity. In this study, capillary electrophoresis (CE) was used for the first time for evaluating myrosinase kinetics (maximum velocity V_max and Michaelis–Menten constant K_m) and to assess the affinity of a variety of substrates toward this enzyme.     

毛细管电泳高频电导法测定尿中MDMA及其代谢物

建立了尿样中MDMA及其代谢物MDA的毛细管电泳高频电导法检测分析方法。对电泳分离缓冲介质的种类、浓度、pH值以及分离操作电压和进样时间等实验条件进行了优化。缓冲液为2．5mmol／L NH4 Ac 0．5mmol／L HAc 2mmol／L SDS 10mmol／L β-CD,分离电压为15kV时,可实现较好的分离与检测。该法在2．5～80μg/mL范围内。MDMA和MDA线性相关系数r分别为0．998和0．999,检出限均为1．0μg/mL(S／N=3)。不同添加浓度水平尿样,日间和日内RSD均小于5％,回收率均在90％以上,适于法医毒物分析和临床药物监测的需要。     

Application of an external contactless conductivity detector for the analysis of beverages by microchip capillary electrophoresis

Quantitative total ionic analysis of alcoholic and nonalcoholic beverages was performed by microchip capillary electrophoresis with external contactless conductivity detection. An electrolyte solution consisting of 10.5 mM histidine, 50 mM acetic acid, and 2 mM 18-crown-6 at pH 4.1 was used for the determination of NH(4) (+), K(+), Ca(2+), Na(+), and Mg(2+). Fast analysis of Cl(-), NO(3) (-), and SO(4) (2-) was achieved in 20 mM 2-(N-morpholino)ethanesulfonic acid /histidine electrolyte solution at pH 6.0 and the simultaneous separation of up to 12 inorganic and organic anions was performed in a solution containing 10 mM His and 7 mM glutamic acid at pH 5.75. Limits of detection ranged from 90 to 250 mug/L for inorganic cations and anions, and from 200 to 2000 mug/L for organic anions and phosphate. Calibration curves showed linear dependencies over one to two orders of magnitude when the stacking effect was minimized by injecting standard solutions prepared in background electrolyte solutions. Total analysis times of 35 and 90 s were achieved for the determination of 5 inorganic cations and for the simultaneous determination of 12 inorganic and organic anions, respectively, which represents a considerable reduction of analysis time compared to conventional separation methods used in food analysis.     

Sample introduction techniques for microchip electrophoresis: A review

The number of applications of microfluidic analysis systems continues to increase, along with the variety of substrate materials and complexity of the devices themselves. One of the most common features of these devices that has remained relatively unchanged, however, is the introduction of a sample mixture into a separation channel so that individual components can be separated by electrophoresis. Whether a relatively simple mixture of amino acids or a more complex sample of DNA fragments extracted and amplified on-chip, the ability to reliably and reproducibly inject a representative sample is arguably the most significant requirement for an electrophoretic micro total analysis system (μTAS). This review will focus on the different methods reported for sample introduction in microchip electrophoresis, highlighting both pressure-driven and electrokinetic techniques, with an emphasis on the methods employed in μTAS applications.     

Anion separations with pressure-assisted capillary electrophoresis using a sequential injection analysis manifold and contactless conductivity detection

It is demonstrated that a hydrodynamic flow superimposed on the mobility of analyte anions can be used for the optimization of analysis time in capillary zone electrophoresis. It was also possible to use the approach for counter‐balancing the electroosmotic flow and this works as well as the use of surface modifiers. To avoid any band‐broadening due to the bulk flow narrow capillaries of 10 μm internal diameter were employed. This was enabled by the use of capacitively coupled contactless conductivity detection, which does not suffer from the downscaling, and detection down to between 1 and 20 μM for a range of inorganic and small organic anions was found feasible. Precisely controlled hydrodynamic flow was generated with a sequential injection manifold based on a syringe pump. Sample injection was carried out with a new design relying on a simple piece of capillary tubing to achieve the appropriate back‐pressure for the required split‐injection procedure.     

液液萃取-场放大进样-毛细管电泳非接触式电导分离检测酱油中的安赛蜜

采用场放大进样(FASI)-毛细管电泳非接触式电导检测法(CE-C⁴D),结合液液萃取(LLE)的样品净化预处理技术,分离检测了酱油中人工合成甜味剂安赛蜜。酱油样品经酸化后,用乙酸乙酯作为萃取剂,成功地消除了酱油中含有的大量无机盐等复杂基体对微量安赛蜜的干扰。实验对影响LLE萃取效率和FASI-CE-C⁴D分离检测的关键因素进行了讨论,特别是对样品净化前处理过程中萃取剂及用量、样品酸化pH值、萃取时间、萃取温度等条件进行了优化。结果表明,酱油中的安赛蜜可获得良好分离和灵敏检测,检出限和定量限分别为0.15 mg/kg和0.48 mg/kg。对市售酱油样品进行安赛蜜的加标回收测定,得到加标回收率为92.3%～108.1%,相对标准偏差<8.0%。该法具有简单快速、灵敏高效、分析成本低的优点,能满足酱油中安赛蜜的分析检测要求。     

Method development and validation for trifluoroacetic acid determination by capillary electrophoresis in combination with capacitively coupled contactless conductivity detection (CE-C4D)

A method was developed to determine traces of trifluoroacetic acid as impurity in synthetic or semi-synthetic drugs as antibiotics, macropeptides, etc. Capillary electrophoresis in combination with capacitively coupled contactless conductivity detection (CE-C⁴D) was used due to lack of UV absorbance property of trifluoroacetic acid (TFA). The optimized method took less than 1 min with good linearity (R² = 0.9995) for trifluoroacetic acid concentration from 2 to 100 ppm. It also has a good repeatability expressed by the relative standard deviation (% RSD) which is 1.2 and 2.1% for intraday and interday precision, respectively, at 50 ppm TFA, and good sensitivity with 0.34 ppm, 1.2 ppm LOD and LOQ, respectively. In addition, the content of TFA in synthetic drug, was determined using the validated method which gave good linearity (R² = 0.9996) for trifluoroacetic acid spiked into drug in a concentration range of 2-80 ppm, with good intraday repeatability of 2.0%.The analysis is performed in a background electrolyte composed of 20 mM morpholinoethane-sulfonic acid (Mes) and 20 mM l-histidine (l-His) pH 6.1. Cetyltrimethylammonium bromide (CTAB) was added as flow modifier in a concentration (0.2 mM) lower than the critical micellar concentration. Ammonium formate 6 ppm was used as internal standard. The applied voltage was 30 kV in reverse polarity. A fused silica capillary with 75 μm internal diameter and total length 47 cm (31 cm to C⁴D detector and 37 cm to DAD detector) was used.     

A thin cover glass chip for contactless conductivity detection in microchip capillary electrophoresis

A microfabricated thin glass chip for contactless conductivity detection in chip capillary electrophoresis is presented in this contribution. Injection and separation channels were photolithographed and chemically etched on the surface of substrate glass, which was bonded with a thin cover glass (100 μm) to construct a new microchip. The chip was placed over an independent contactless electrode plate. Owing to the thinness between channel and electrodes, comparatively low excitation voltage (20–110 V in V_p–p) and frequency (40–65 kHz) were suitable, and favorable signal could be obtained. This microchip capillary electrophoresis device was used in separation and detection of inorganic ions, amino acids and alkaloids in amoorcorn tree bark and golden thread in different buffer solutions. The detection limit of potassium ion was down to 10 μmol/L. The advantages of this microchip system exist in the relative independence between the microchip and the detection electrodes. It is convenient to the replacement of chip and other operations. Detection in different position of the channel would also be available.     

基于智能手机的便携式毛细管电泳装置检测消毒剂中2种季铵盐

现有的小型毛细管电泳(CE)装置仍采用平板或计算机进行数据处理和分析,其便携性仍存在明显不足.针对这一问题,发展了一种基于智能手机的CE装置,实现了真正的便携式定量分析.该装置集成了电容耦合式非接触式电导检测(C4 D)和蓝牙通信功能,并提供了手机界面软件.通过手机界面软件,不仅可以控制CE装置的电泳运行,还可以实时接...     

Determination of the spectrum of low molecular mass organic acids in urine by capillary electrophoresis with contactless conductivity and ultraviolet photometric detection--an efficient tool for monitoring of inborn metabolic disorders

A mixture of 29 organic acids (OAs) occurring in urine was analyzed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C⁴D) and UV photometric detection. The optimized analytical system involved a 100 cm long polyacrylamide-coated capillary (50 μm i.d.) and the background electrolyte of 20 mM 2-morpholinoethanesulfonic acid (MES)/NaOH + 10% (v/v) methanol, pH 6.0 (pH is related to the 20 mM MES/NaOH buffer in water). The LOD values obtained by C⁴D for the OAs which do not absorb UV radiation range from 0.6 μM (oxalic acid) to 6.8 μM (pyruvic acid); those obtained by UV photometry for the remaining OAs range from 2.9 μM (5-hydroxy-3-indoleacetic acid) to 10.2 μM (uric acid). The repeatability of the procedure developed is characterized by the coefficients of variation, which vary between 0.3% (tartaric acid) and 0.6% (5-hydroxy-3-indoleacetic acid) for the migration time and between 1.3% (tartaric acid) and 3.5% (lactic acid) for the peak area. The procedure permitted quantitation of 20 OAs in a real urine sample and was applied to monitoring of the occurrence of the inborn metabolic fault of methylmalonic aciduria.     

Low-cost and versatile analytical tool with purpose-made capillary electrophoresis coupled to contactless conductivity detection: Application to antibiotics quality control in Vietnam

In this study, the development of our purpose-made capacitively coupled contactless conductivity detection (C⁴D) for CE is reported. These systems have been employed as a simple, versatile, and cost-effective analytical tool. CE-C⁴D devices, whose principle is based on the control of the ion movements under an electrical field, can be constructed even with a modest financial budget and limited infrastructure. A featured application was developed for quality control of antimicrobial drugs using CE-C⁴D, with most recent work on determination of aminoglycoside and glycopeptide antibiotics being communicated. For aminoglycosides, the development of CE-C⁴D methods was adapted to two categories. The first one includes drugs (liquid or powder form) for intravenous injection, containing either amikacin, streptomycin, kanamycin A, or kanamycin B. The second one covers drugs for eye drops (liquid or ointment form), containing either neomycin, tobramycin, or polymyxin. The CE-C⁴D method development was also made for determination of some popular glycopeptide antibiotics in Vietnam, including vancomycin and teicoplanin. The best detection limit achieved using the developed CE-C⁴D methods was 0.5 mg/L. Good agreement between results from CE-C⁴D and the confirmation method (HPLC- Photometric Diode Array ) was achieved, with their result deviations less than 8% and 13% for aminoglycoside and glycopeptide antibiotics, respectively.     

Determination of Ca, K, Mg, Na, sulfate, phosphate, formate, acetate, propionate, and glycerol in biodiesel by capillary electrophoresis with capacitively coupled contactless conductivity detection

In this work, a new method employing capillary electrophoresis (CE) for the determination of several species in biodiesel is introduced. The concentrations of inorganic species (Na⁺, K⁺, Ca²⁺, Mg²⁺, SO₄²⁻, and PO₄³⁻) and glycerol are of interest to the regulatory authorities due to their ability to form undesirable compounds in engines. Additionally, other species of low molecular weight (e.g., acetate, formate, and propionate) are of interest because they contribute towards increasing the acidity. These species are formed by the degradation of biodiesel and cause damage to engines and the environment. The cation separation was performed in background electrolyte (BGE) composed of 30 mmol L⁻¹ of 2-(n-morpholino)ethanesulfonic acid (MES)/L-histidine (His), pH 6. The separation of anionic species was carried out in similar BGE with 0.2 mmol L⁻¹ cetyltrimethylammonium bromide (CTAB) added. For glycerol, a neutral species, its oxidation with periodate was employed. This well-known reaction is specific to polyols and generates iodate. The amount of iodate produced by the reaction was determined by CE. The separation was carried out in approximately 1 min using BGE composed of 30 mmol L⁻¹ acetic acid, pH 3. The analytical parameters evaluated were: linearity (r > 0.99), the RSD values for area and migration time were < 3.4% and 0.9%, respectively, and recovery was in the range of 89 to 107%.     

多通道非接触电导检测装置用于自由流电泳分离在线检测

现有自由流电泳(FFE)装置因不具备在线检测功能,其实用性仍然存在明显不足.针对这一问题,该工作发展了一种多通道电容耦合式非接触电导检测(MC-C4 D)装置并开发了自动测量软件.MC-C4 D装置采用了并行分时的非接触电导检测技术,即由多个同样的非接触电导检测模块并行排列,而单个电导检测模块又由多个非接触电导检测池组...     

Simple in‐house flow‐injection capillary electrophoresis with capacitively coupled contactless conductivity method for the determination of colistin

An in‐house flow‐injection capillary electrophoresis with capacitively coupled contactless conductivity detection method was developed for the direct measurement of colistin in pharmaceutical samples. The flow injection and capillary electrophoresis systems are connected by an acrylic interface. Capillary electrophoresis separation is achieved within 2 min using a background electrolyte solution of 5 mM 2‐morpholinoethanesulfonic acid and 5 mM histidine (pH 6). The flow‐injection section allows for convenient filling of the capillary and sample introduction without the use of a pressure/vacuum manifold. Capacitively coupled contactless conductivity detection is employed since colistin has no chromophore but is cationic at pH 6. Calibration curve is linear from 20 to 150 mg/L, with a correlation coefficient (r²) of 0.997. The limit of quantitation is 20 mg/L. The developed method provides precision, simplicity, and short analysis time.