Recent advances in amino acid analysis by capillary electrophoresis

This paper describes the most important articles that have been published on amino acid analysis using CE during the period from June 2009 to May 2011 and follows the format of the previous articles of Smith (Electrophoresis 1999, 20, 3078-3083), Prata et al. (Electrophoresis 2001, 22, 4129-4138) and Poinsot et al. (Electrophoresis 2003, 24, 4047-4062; Electrophoresis 2006, 27, 176-194; Electrophoresis 2008, 29, 207-223; Electrophoresis 2010, 31, 105-121). We present new developments in amino acid analysis with CE, which are reported describing the use of lasers or light emitting diodes for fluorescence detection, conductimetry electrochemiluminescence detectors, mass spectrometry applications, and lab-on-a-chip applications using CE. In addition, we describe articles concerning clinical studies and neurochemical applications of these techniques.     

Recent advances in amino acid analysis by capillary electrophoresis

Amino acids are studied extensively using capillary electrophoresis. In this review we will report the different researchs which have been done in the literature since 1998. We will describe the developments of, detection methods, separations of enantiomers, the new medical applications, and amino acids in food and plants.     

Recent advances in amino acid analysis by capillary electrophoresis

Amino acids are studied extensively using capillary electrophoresis. In a previous article, we reviewed applications reported in the period 1999-early 2001 (Prata, C., Bonnafous, P., Fraysse, N., Treilhou, M., Poinsot, V., Couderc, F., Electrophoresis 2001, 22, 4129-4138). In this article we follow on with this review for the period end of 2001-beginning of 2003. We will report the developments of detection methods, separations of enantiomers, the new medical applications, and amino acids in food and plants. This review shows that CE is more and more important for the amino acid analysis.     

Recent advances in amino acid analysis by capillary electrophoresis

This paper describes a number of articles that have been published on amino acid analysis using CE during the period from June 2003 to May 2005. This review article follows the previous ones of Smith (Electrophoresis 1999, 20, 3078-3083), Prata et al. (Electrophoresis 2001, 22, 4129-4138), and Poinsot et al. (Electrophoresis 2003, 24, 4047-4062). Several new developments in amino acid analysis with CE are reported concerning UV detection, LIF, MS, and NMR. In addition, we describe articles concerning clinical and pharmaceutical studies, neuroclinical applications, and agricultural and food analysis.     

Pesticide analysis by capillary electrophoresis

In this work, a critical and updated revision of the current situation of the analysis of pesticides by Capillary Electrophoresis (CE) is presented. The review has been written in two main sections. The first one presents a thorough revision of the various offline and on-line sample preconcentration procedures that have been used in conjunction with CE to analyze these compounds. The second part reviews the various detection strategies (i.e., UV, LIF, MS, and electrochemical) and CE modes that have been applied to the analysis of pesticides. Future trends that can be expected from this hot research area are also discussed.     

Peptide nucleic acid and amino acid modified peptide nucleic acid analysis by capillary zone electrophoresis

A rapid, high resolution, and low sample consumption CZE method is developed for peptide nucleic acid (PNA) analysis for the first time. 30% v/v acetonitrile in PNA sample and 20% v/v acetonitrile in 50 mM borax‐boric acid (pH 8.7) as BGE were employed after optimization. The calibration curves were linear for PNA concentration ranging from 1 to 50 μmol/L. LOD and LOQ of PNA were 0.2 and 1.0 μmol/L, respectively. Since the commercially available reagent gives rise to huge PNA peak and an apparent impurity peak, the purity of PNA was evaluated to be about 81.4% by CZE method, obviously lower than the supplier's purity value of 99.9% evaluated by RP–HPLC, and also lower than 94.8% determined with RP–HPLC by our research group. The CZE method takes only 5 min, needs only 90 nL PNA, much less than 20 min and 20 μL PNA in RP–HPLC method. Moreover, the CZE method is applicable for the analysis of glutamic acid modified and lysine modified PNAs, they show different migration time with their corresponding complementary PNAs. Our results show CZE provides a new choice for PNA and modified PNA analysis, also their purity or quality evaluation.     

Large-volume sample stacking for analysis of ethylenediaminetetraacetic acid by capillary electrophoresis

A simple, quick, and sensitive capillary electrophoretic technique-large volume stacking using the electroosmotic flow (EOF) pump (LVSEP) - has been developed for determining ethylenediaminetetraacetic acid (EDTA) in drinking water for the first time. It is based on a precapillary complexation of EDTA with Fe(III) ions, followed by large-volume sample stacking and direct UV detection at 258 nm. The curve of peak response versus concentration was linear from 5.0 to 600.0 microg/L, and 0.7 to 30.0 mg/L. The regression coefficients were 0.9988 and 0.9990, respectively. The detection limit of the current technique for EDTA analysis was 0.2 microg/L with an additional 10-fold preconcentration procedure, based on the signal-to-noise ratio of 3. As opposed to the classical capillary zone electrophoresis (CE) method, the detection limit was improved about 1000-fold by using this LVSEP method. To the best of our knowledge, it represents the highest sensitivity for EDTA analysis via CE. Several drinking water samples were tested by this novel method with satisfactory results.     

Energy drink analysis by capillary electrophoresis

Caffeine and vitamins C, PP, and B6 have been determined in energy drinks by capillary electrophoresis. Its advantages and disadvantages over high-performance liquid chromatography have been considered and the influence of analysis conditions on the error of analysis and error sources in capillary electrophoresis have been estimated.     

Element speciation analysis by capillary electrophoresis

An overview of recent developments in the application of capillary electrophoresis to simultaneous separation and determination of different chemical forms of an inorganic element is presented, with particular emphasis placed on metal speciation analysis. Examples of species analysis are addressed, covering metal ions in different oxidation states, metal complexes with inorganic and organic ligands, metalloid oxoanions, organometallic compounds, ionic non-metal species, etc. The speciation performance of capillary electrophoresis is illustrated by a number of practically relevant applications. The method's strengths and current limitations with regard to chemical speciation studies are critically discussed.     

Stereoselective analysis of acid herbicides in natural waters by capillary electrophoresis.

A capillary electrophoretic method for the stereoselective analysis of aryloxypropionic and aryloxyphenoxypropionic acidic herbicides in ground water and river water was performed. Vancomycin and gamma-cyclodextrin were added to the background electrolyte (BGE) as chiral selectors. Water sample preconcentration was accomplished by solid-phase extraction on styrene-divinylbenzene packed cartridges (2 L of ground water and 1 L of river water). The analytical method allowed for the resolution of mecoprop, fenoprop, fluazifop and haloxyfop racemic mixtures in natural water samples spiked with enantiomer concentration levels in the range 0.1-0.13 ppb for ground water and 0.4-0.54 ppb for river water.     

Recent advancements in amino acid analysis using capillary electrophoresis

Recent advances in the analysis of amino acids using capillary electrophoresis are addressed. This area of research continues to receive increased attention as is evident from the 62 references reviewed. This review discusses current detection strategies including UV absorbance, laser-induced fluorescence, electrochemical, and others. Separation methodologies for both derivatized and underivatized amino acids are reviewed. Both direct and indirect enantiomeric resolution of amino acids are addressed. Applications utilizing capillary electrophoresis for the analysis of amino acids are discussed. This review covers literature published in 1997 and 1998.     

Home-made capillary array electrophoresis for high-throughput amino acid analysis

A capillary array electrophoresis (CAE) with confocal rotary scanner for high-throughput carboxytetramethylrhodamine succinimidyl ester (TAMRA)-labeled amino acid (AA) analysis is presented. Performance of the CAE setup was evaluated with AA samples. Up to 128 capillaries could be detected in parallel. For the first time, the device was applied to separate the enantiomers of isoleucine, cysteine, and glutamic acid with cyclodextrin-modified electrolytes by capillary zone electrophoresis. Baseline separation of seven AAs is also demonstrated using micellar electrokinetic chromatography method.     

Pesticides analysis by liquid chromatography and capillary electrophoresis

Nowadays, a wide range of pesticides are used in agricultural production, and their monitoring in samples of environmental and alimentary interest is of extreme importance to ensure, among others, the safety of consumption of foods. The aim of this work is to provide updated information about the major developments in CE and HPLC in pesticide analysis, covering relevant publications between 2004 and early 2006. The use of different sample pretreatment steps to provide a suitable extraction of these compounds from the different matrices as well as to increase the sensitivity of the determination is also discussed.     

Determination of aristolochic acid by capillary zone electrophoresis

A simple and rapid capillary zone electrophoresis (CZE) method for the determination of aristolochic acid (AA) in dietary supplements and selected herbs is described. A clear separation of AA from other sample constituents was achieved within 5 minutes without any sample clean up. A mixture of 20 mM-morpholinethanesulphonic acid+10 mM-BisTrisPropane+0.2% hydroxyethylcelullose in 10% methanol serves as a background electrolyte. The linearity, accuracy, intra-assay and detection limit of the developed method are 200–6000 ng/mL, 95–103%, 3.5%, and 50 ng/ml, respectively. Ease of use, sufficient sensitivity and low running cost are the most important attributes of the CZE method. The proposed CZE method was compared with HPLC.     

High-throughput analysis of telomerase by capillary electrophoresis

The enzyme telomerase is expressed in (85-90)% of all human cancers, but not in normal, non-stem cell somatic tissues. Clinical assays for telomerase in easily obtained body fluids would have great utility as noninvasive, cost-effective methods for the early detection of cancer. The most commonly used method for the detection and quantification of telomerase enzyme activity is the polymerase chain reaction (PCR)-based assay known as the telomerase repeat amplification protocol or TRAP assay. Most of the TRAP assay systems use a slab-gel based electrophoresis system to size and quantify the PCR-amplified extension products. We are developing high-throughput capillary electrophoresis (CE) methods for the analysis of TRAP/PCR products. The TRAP assay was conducted on lysates of the human lung cancer cell line A-549 in reactions containing 5-100 cells. TRAP/PCR products were generated using a fluorescent 4,7,2'4'5'7',-hexachloro-6-carboxyfluorescein(HEX)-labeled TS primer and analyzed on the Applied Biosystems Model 310 CE system using POP4 polymer. After analysis with GeneScan and Genotyper software, the total peak areas of the TRAP ladder extension products were computed using Microsoft Excel. Results were compared with unlabeled TRAP/PCR products analyzed on the Bio-Rad BioFocus 3000 CE system using 6% high molecular weight polyvinylpyrrolidone (HMW PVP) polymer and SYBR Green I dye. Both CE systems were able to resolve the TRAP ladder products with high reproducibility and sensitivity (5-15 cells). With the appropriate robotic sample handling system, these CE methods would enable performing the telomerase TRAP assay with increased sensitivity, reproducibility and automation over slab-gel methods.     

Determination of acid dissociation constants by capillary electrophoresis

Capillary electrophoresis affords a simple, automated approach for the measurement of pKa values in the range 2-11 at a throughput of less than 1 h per sample per instrument. Agreement with literature values is usually within 0.20 log units with a precision better than 0.07 log units. The attractive features of capillary electrophoresis for pKa measurements are: (1) conventional instrumentation with a high level of automation are suitable for all measurements; (2) because it is a separation method samples need not be of high purity; (3) samples of low water solubility with suitable chromophores are easily handled (detection limits in the microM range); (4) sample consumption per measurement is in the microgram range; and (5) since only mobilities are measured, exact knowledge of concentrations is not needed. The general approach can be extended to pKa measurements in aqueous-organic solvent mixtures and non-aqueous solvents with suitable calibration. The widespread use of absorbance detection in capillary electrophoresis means that the sample must have a suitable chromophore for detection. The main source of controllable error is the accuracy of buffer standardization and their stability in use, and uncontrollable error, the retentive interactions of the sample with the column wall. The latter seems to be a rare problem in practice for typical operating conditions.     

Tear analysis of ascorbic acid,uric acid and malondialdehyde with capillary electrophoresis

Tears have a significant role in antioxidant defense in ocular tissues and since their collection is quick and noninvasive, their analysis would facilitate monitoring of pathophysiological changes. However, their low volume and low content of antioxidants makes analysis difficult; methods of high sensitivity are needed. In this paper, we present a method for tear analysis of two antioxidant molecules (ascorbic and uric acid) and of a lipid peroxidation indicator (malondialdehyde) with capillary electrophoresis. Tears were collected with Schirmer strips, extracted with a low‐pH phosphate buffer, centrifuged through membrane filters and an antioxidant was added. They were stable at ?70°C for 15 days. After pilot experiments, optimum electrophoretic separation was achieved in a 25 mm borate buffer, pH 10.0, containing 100 mm sodium dodecyl sulfate at 25°C and 20 kV. The developed method has good repeatability (<5% RSD), precision (<15% relative error values) and high sensitivity (LLOQ values of 20, 2.3 and 2.5 μM for ascorbate, urate and malondialdehyde, respectively). It was applied to the analysis of tears from healthy individuals and the antioxidant levels are in agreement with those obtained with other techniques. This method might serve as a tool to clarify the role of endogenous antioxidants in the pathophysiology of ocular diseases. Copyright © 2009 John Wiley & Sons, Ltd.