Determination of impurities and counterions of pharmaceuticals by capillary electromigration methods

The review presents a survey of recent applications of high‐performance capillary electromigration methods—capillary zone electrophoresis, nonaqueous capillary electrophoresis, capillary isotachophoresis, micellar electrokinetic chromatography, microemulsion electrokinetic chromatography and capillary electrochromatography—for the determination of impurities of pharmaceuticals, including chiral impurities, for the period 2007–2013. In addition, due to the missing evaluation of the determination of counterions of pharmaceuticals by capillary electromigration methods in the last 20 years, the publications dealing with this topic since 1995 are included in this review. General aspects of both these types of applications of capillary electromigration methods in pharmaceutical analysis are discussed, and detailed experimental conditions used for determination of various chemical impurities and counterions of many particular drugs are described.     

A new capillary electrophoresis end-column amperometric detection system without the need for capillary/electrode alignment

A self-aligning end-column amperometric detection system for capillary electrophoresis was constructed. In this system, the electrode and capillary were exchanged easily and the capillary/electrode alignment procedure is not required. Gold, gold/mercury amalgam, copper and carbon fiber could be used as the working electrode. The principle is in the use of two disk holders with the capillary and the electrode in the center, so that by inserting the disk holders into a groove in the working electrode port, the capillary and the electrode are automatically aligned and the distance between the capillary and the electrode is assured at 0.24 mm. The relative standard deviation obtained using five different gold/mercury amalgam microdisk electrodes for determination of cysteine was 1.5% for the migration time and 3.3% for the electrophoretic peak current. The simple and convenient system was attractive for the routine analysis by capillary electrophoresis with electrochemical detection. The system was applied to the determination of promethazine hydrochloride in human serum.     

Determination of tea catechins

An overview of analytical methods for the measurement of biologically important tea catechins is presented. Liquid chromatography and capillary electrophoresis are the most cited techniques for catechin separation, identification and quantitation. Liquid chromatography with ultraviolet detection is frequently used; however, mass spectrometry, electrochemical, fluorescence and chemiluminescence detection are also utilized in cases where more sensitive or selective detection is needed. Two modes of capillary electrophoresis, capillary zone electrophoresis and micellar electrokinetic capillary chromatography, have been employed for the determination of catechins. Both modes of capillary electrophoresis are based on ultraviolet detection. Additional analytical techniques, such as gas chromatography, thin-layer chromatography, paper chromatography, spectrophotometry, biosensing, chemiluminescence and nuclear magnetic resonance spectroscopy have also been utilized for the determination of catechins and are reviewed herein.     

Capillary zone electrophoresis with electrochemical detection for the determination of glutathione in human red blood cells without preseparation of hemoglobin

Interference is studied for the determination of glutathione (GSH) in human red blood cells by using capillary zone electrophoresis with end-column amperometric detection at a gold-mercury amalgam microelectrode. It is found that when interference substances such as hemoglobin (Hb) in the hemolysate flow off from the end of the separation capillary, they can be adsorbed on the surface of the electrode and interfere with the signal of GSH. If the concentration of hemolysate is lower than 0.5% (v/v), this phenomenon can be overcome because they are adsorbed on the surface of the capillary wall and do not flow off from the capillary. A method is developed for the determination of GSH in human erythrocytes without the preseparation of Hb.     

毛细管超薄池光度吸附测量新技术

在毛细管超薄池光度检测中首次采用吸收光强测量新技术,显著提高了测量的灵敏度和改善了信噪比。在内径50μm的石英毛细管超薄池以及由石英光导纤维构成的十字交叉超薄光学吸收池上,分别测量了系列高锰酸钾溶液吸收光强。吸收光强与高锰酸钾溶液浓度之间呈现良好的线性关系。对于10μg/mL的高锰酸钾稀溶液,毛细管超薄池吸收光强测量的信噪比相对于吸光度测量的有较大的改善。十字交叉池的光程约为40μm,容积约为0.02μL,具有较大的光能量,可望发展成为一种新型的电泳光度检测池。     

Rapid determination of aliphatic amines in water samples by pressure-assisted monolithic octadecylsilica capillary electrochromatography-mass spectrometry

A pressure-assisted capillary chromatography-mass spectrometry method based on the use of a monolithic octadecylsilica (ODS) capillary is proposed for the determination of aliphatic amines. A 25 mM citric acid buffer containing 10% methanol is used as running electrolyte. Separation is achieved by simultaneously applying a capillary electrophoresis (CE) voltage of 13 kV and an overimposed pressure of 8 bar. The use of pressure is required to ensure stable electrospray conditions. Analysis times are reduced by using a capillary column consisting of a 30 cm long monolithic silica capillary column bound with ODS and a fused-silica capillary column also 30 cm long. The proposed method was successfully applied to the determination of low-molecular-weight aliphatic amines in tap and river water. The analysis of real samples requires cleanup and preconcentration, which can be performed automatically by inserting a minicolumn in the replenishment system of the commercial instrument.     

Analytical potential of enzyme-coated capillary reactors in capillary zone electrophoresis

Enzymes immobilized on the inner surface of an electrophoretic capillary were used to increase sensitivity and resolution in capillary zone electrophoresis (CZE). Sensitivity is enhanced by inserting a piece of capillary containing the immobilized enzyme into the main capillary, located before the detector, in order to transform the analyte into a product with a higher absorptivity. This approach was used to determine ethanol. In order to improve resolution, capillary pieces containing immobilized enzymes were inserted at various strategic positions along the electrophoretic capillary. On reaching the enzyme, the analyte was converted into a product with a high electrophoretic mobility, the migration time for which was a function of the position of the enzyme reactor. This approach was applied to the separation and determination of acetaldehyde and pyruvate. Finally, the proposed method was validated with the determination of ethanol, acetaldehyde, and pyruvate in beer and wine samples.     

毛细管气相色谱法测定12种农药的有效成分

 建立了毛细管气相色谱法测定速克灵、戊唑醇等 12种农药中有效成分的方法。采用SE 3 0大口径毛细管柱和火焰离子化检测器 (FID) ,内标法定量 ,气相色谱 /质谱法定性确证 ,样品加标的平均回收率为 99 2 0 %～10 2 4 4 % ,相对标准偏差为 0 0 7%～ 5 4 9%。该方法简单快速 ,结果准确 ,可作为测定单样、复配样农药或同时测定多种农药有效成分的通用方法     

Determination of Catecholamines by Capillary Electrophoresis-Mass Spectrometry

A method for determination of catecholamines (adrenaline, noradrenaline, and dopamine) by capillary electrophoresis-electrospray ionization-mass spectrometry is described. The electrospray operating mode is optimized as well as the system for capillary electrophoresis.     

Off-line and in-line determination of catechol- O-methyltransferase activity in a capillary electrophoretic system

The use of capillary electrophoresis for the determination of catechol-O-methyltransferase (COMT) activity with dihydroxybenzoic acid as a substrate was investigated. Both an off-line and in-line capillary electrophoresis determination of COMT activity was developed and the two approaches are discussed. In the presented methods, substrate and reaction products are monitored at the same time. The initial velocity of the reaction is quantified spectrophotometrically by the corrected peak area of the products at 200 nm. In the off-line setup, capillary zone electrophoresis is used to separate and quantify the different reaction compounds. Each electrophoretic run required only 37 nL of the enzymatic reaction solution. Based on the off-line assay, an in-line determination of COMT activity was developed by a methodology known as electrophoretically mediated microanalysis (EMMA). All the different steps (i.e. mixing, incubation, separation and in-line quantitation) are combined in the capillary, which is used as a microreactor for the enzymatic reaction. Full automation of the assay is achieved with this microscale approach.     

Application of capillary isotachophoresis and capillary zone electrophoresis to the determination of inorganic ions in food and feed samples

The purpose of this review is to summarise critically the possibilities of capillary isotachophoresis and capillary zone electrophoresis for the determination of inorganic ions in food and feed samples. This article covers papers published since 1977.     

Incorporation of Disposable Screen‐Printed Electrodes for Use in Capillary Electrophoresis End‐Column Amperometric Detection System

The development and performance of an end‐column amperometric detection system integrated with disposable screen‐printed electrodes for capillary electrophoresis is presented. In this system, the electrode and capillary can be easily replaced and the capillary/electrode alignment procedure is straightforward. The use of easily replaceable screen‐printed electrodes offers a tremendous benefit for capillary electrophoresis applications requiring frequent replacement of the working electrode due to fouling. This simple and convenient system is very attractive for routine analyses by capillary electrophoresis with electrochemical detection. The separation and determination of uric acid in human urine is presented.     

A fast high throughput method for the determination of acidity constants by capillary electrophoresis. 3. Basic internal standards

A set of 25 monoprotic bases is proposed as internal standards for pK(a) determination by capillary electrophoresis. The pK(a) of the bases is determined and compared with available literature data. The capillary electrophoresis internal standard method offers numerous advantages over other typical methods for pK(a) determination, especially of analysis time and buffer preparation. However, it requires disposing of appropriate standards with reference pK(a) value. The set of bases established in this work together with the set of acids previously established provide a reference set of compounds with well-determined acidity constants that facilitate the process of selecting appropriate internal standards for fast pK(a) determination by capillary electrophoresis in high throughput screening of pharmaceutical drugs. In addition, the performance of the method when acidic internal standards are used for the determination of acidity constants of basic internal standards has also been tested. Although higher errors may be expected in this case, good agreement is observed between determined and literature values. These results indicate that in most cases structural similarity between the analyte and the internal standard might not be an essential requirement in the internal standard method.     

Determination of Pyromellitic Acid in Aqueous Matrices by CE

An analytical method for the capillary electrophoresis determination of pyromellitic acid in aqueous media used as “food simulants” has been developed and is described in this paper. The proposed method determined the pyromellitic acid at ppb levels and is based on a capillary zone electrophoresis separation using coated fused-silica capillary column with a carbonate running buffer and a UV-Vis detector. The method herein developed has been applied to the determination of pyromelitic acid residues leached from plastic bottles. The amount of pyromellitic acid determined in different batch of polyethyleneterephthalate bottles is 2.18%, while the limit of detection is 2.30 ng mL^?1 with a relative standard deviation of 4.40%.     

Prediction of Migration Times of Organic Ions in Capillary Zone Electrophoresis

The electrophoretic mobility ratio (R value) of any two ions is constant and independent of the capillary type and electrophoretic conditions if their electrical charges and hydration radii are constant. The use of strong acid salts and quaternary ammonium salts is therefore proposed for the determination of R values. Such analytes are called markers. The following determinations can be carried out: (i) the determination of the migration time corresponding to the electroosmotic flow (EOF) in any capillary under any electrophoretic condition by measuring the migration times of two markers in the condition studied (useful when the EOF is weak); (ii) the determination of the migration time of an analyte in any capillary by knowing the migration time of the markers in the capillary studied. If the pH is changed and the ionization of the analyte is pH dependent, the resulting migration time for the analyte can be calculated. The constancy of the mobility ratios of seven markers was checked experimentally at eight different pH values (between pH 3 and 10), at three temperatures, and for two buffer concentrations. The predicted and experimental migration times were also compared in two different types of capillaries.     

Application of capillary isotachophoresis for fruit juice authentication

A method using capillary isotachophoresis (ITP) was developed and applied for the determination of the anionic profile of orange juices with the aim to obtain some useful information on the authenticity or adulteration of imported and native beverage products. An EA 100 electrophoretic analyser (Villa-LABECO, Slovak Republic) was used for capillary isotachophoretic determination of anions in tested samples. More systems of leading and terminating electrolytes were used. Detection conductivity and UV detection at 254 nm were used. Sample injection volume was 30 microl. These systems allow one to determinate inorganic anions, organic acids and some additives--adulterants in anionic forms in orange juices. By capillary isotachophoretic determination the lengths or areas of characteristic zones were established and compared to authentic orange juices of different species and origin and with RSK reference values (Code of Practice). Special emphasis was placed on D-isocitric acid ITP determination as a reliable fruit juice authentication marker. The presented multicomponent analysis of orange juice authenticity according to ITP anionic profiles obtained by capillary isotachophoresis presents an alternative information source necessary for deciding about authenticity of the products.     

基于丙酮酸/还原型辅酶I/乳酸脱氢酶/氧化型辅酶I/乳酸正逆反应同时测定丙酮酸/乳酸的酶荧光毛细管分析

利用丙酮酸(PA)/还原型辅酶I(NADH)/乳酸脱氢酶(LDH)/氧化型辅酶I(NAD+)/乳酸(LA)荧光反应体系的正逆反应,建立了一种可直接用于临床检验、能同时测定血清中微量PA/LA的酶荧光毛细管分析法.本方法可在常规荧光光度计上,用普通玻璃毛细管同时实现了PA/LA的高灵敏分析,每次分析试剂和样品的用量仅9 ...     

毛细管电泳-电喷雾质谱联用技术及其在蛋白质分析领域中的应用

综述了毛细管电泳与电喷雾质谱联用的接口技术、分离模式及其在蛋白质分析领域中的应用，特别是毛细管等电聚焦与电喷雾质谱联用在蛋白质组学中研究进展。     

The identification and determination of selected 1,4-benzodiazepines by an optimised capillary electrophoresis-electrospray mass spectrometric method

An optimised capillary electrophoresis-electrospray mass spectrometric method is presented for the identification and determination of diazepam and its metabolites N'-desmethyldiazepam, oxazepam and temazepam. By investigating constituent parts of the capillary electrophoresis-electrospray mass spectrometric interface and optimising their function, a relatively fast and reproducible method is described for the identification and determination of selected 1,4-benzodiazepines. Optimisation of sheath and auxiliary gas flows, capillary tip tapering, capillary tip positioning, sheath liquid composition and flow rate and pressure application during the separation step have led to acceptable relative standard deviation (RSD) values for migration time and peak area, correlation coefficients and limits of detection. This has been achieved as a result of stabilising the electrospray current prior to analysis, a procedure that takes a matter of minutes when using the method described. Sequential product ion fragmentation (MS(n)) characterisation of 15 1,4-benzodiazepines is also presented and mechanisms for the observed fragmentation patterns proposed.     

A replaceable dual-enzyme capillary microreactor using magnetic beads and its application for simultaneous detection of acetaldehyde and pyruvate

A novel replaceable dual-enzyme capillary microreactor was developed and evaluated using magnetic fields to immobilize the alcohol dehydrogenase (ADH)- and lactate dehydrogenase (LDH)-coated magnetic beads at desired positions in the capillary. The dual-enzyme assay was achieved by measuring the two consumption peaks of the coenzyme β-nicotinamide adenine dinucleotide (NADH), which were related to the ADH reaction and LDH reaction. The dual-enzyme capillary microreactor was constructed using magnetic beads without any modification of the inner surface of the capillary, and showed great stability and reproducibility. The electrophoretic resolution for different analytes can be easily controlled by altering the relative distance of different enzyme-coated magnetic beads. The apparent K(m) values for acetaldehyde with ADH-catalyzed reaction and for pyruvate with LDH-catalyzed reaction were determined. The detection limits for acetaldehyde and pyruvate determination are 0.01 and 0.016 mM (S/N = 3), respectively. The proposed method was successfully applied to simultaneously determine the acetaldehyde and pyruvate contents in beer samples. The results indicated that combing magnetic beads with CE is of great value to perform replaceable and controllable multienzyme capillary microreactor for investigation of a series of enzyme reactions and determination of multisubstrates.