A sulfonated capillary that gives reproducible migration times for capillary zone electrophoresis and micellar electrokinetic chromatography

Development of a CZE-ESI-MS assay with a sulfonated capillary for profiling picolinic acid and quinolinic acid formation in multienzyme system

This article describes the development of a reliable CZE-ESI-MS method to simultaneously separate and quantitate three specific metabolites (3-hydroxyanthranilic acid (3-HAA), quinolinic acid (QA), and picolinic acid (PA)) of the kynurenine pathway (KP) of tryptophan catabolism. Using a covalently bonded sulfonated capillary, the parameters such as pH, type of background electrolyte, type of organic solvent, nebulizer pressure as well as both negative and positive ESI-MS modes were optimized to achieve the best Rs and S/N of three KP metabolites. The developed CZE-ESI-MS assay provided high resolution of PA/QA, high specificity, a total analysis time of 10 min with satisfactory intraday and interday repeatability of migration time and peak areas. Under optimized CZE-ESI-MS conditions, the calibration curves over a concentration range of 19-300 μM for 3-HAA and QA, and 75-300 μM for PA were simultaneously generated. The method was successfully applied for the first time to profile the concentrations of initial substrate, 3-HAA, and its eventual products, PA and QA, formed in the complex multienzyme system. As the ratio of two enzymes, 3-hydroxyanthranilate 3,4-dioxygenase (HAO) and α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) decreases, the concentration of QA approaches essentially zero indicating that all ACMS formed by the action of HAO is consumed by ACMSD rather than its spontaneous decay to QA.

Enantioseparation of α-hydroxy acids by chiral ligand exchange CE with a dual central metal ion system

Using two kinds of central metal ions in a background electrolyte, ligand exchange CE was investigated for the simultaneous enantioseparation of dl-malic, dl-tartaric, and dl-isocitric acids. Ligand exchange CE with 100 mM d-quinic acid as a chiral selector ligand and 10 mM Cu(II) ion as a central metal ion could enantioseparate dl-tartaric acid but not dl-malic acid or dl-isocitric acid. A dual central metal ion system containing 0.5 mM Al(III) ion in addition to 10 mM Cu(II) ion in the background electrolyte enabled the simultaneous enantioseparation of the three α-hydroxy acids. These results suggest that the use of a dual central metal ion system can be useful for enantioseparation by ligand exchange CE.

Quantitative analysis of anionic metabolites for Catharanthus roseus by capillary electrophoresis using sulfonated capillary coupled with electrospray ionization-tandem mass spectrometry

This paper describes a practical method to quantify anionic metabolites using contemporary capillary electrophoresis-electrospray ionization-tandem mass spectrometry (CE-ESI-MS/MS). The use of sulfonated capillary permitted a simultaneous analysis of sugar phosphates, organic acids, nucleotides and coenzyme A compounds with only one CE condition. This capillary also improved the repeatability and sensitivity. MS/MS with multiple reaction monitoring (MRM) detection was utilized to achieve significant selectivity and sensitivity. Under optimized CE-ESI-MS/MS system, the detection limits of 53 metabolites at signal-to-noise ratio of 3 were between 0.040 and 8.8 mumol/l. The relative standard deviations (RSDs) for the majority anionic metabolites were better than 0.5% for migration times, and better than 10.0% for peak areas (n=6). Matrix effects by contaminants in sample solution in CE-ESI-MS/MS analysis were removed dramatically by the sample preparation method with liquid-liquid fractionation and ultrafiltration procedure. Furthermore, the developed method was successfully applied to determine anionic metabolites in a cultured cell of Catharanthus roseus. Accumulation of some metabolites including shikimate, malate, and sedoheptulose 7-phosphate by elicitation of methyl jasmonate was observed. The result would show shikimate, tricarboxylic acid and pentose phosphate pathways were activated. Our method will be useful for detailed analysis of primary metabolism dynamics.

MEKC: An update focusing on practical aspects

This paper reviews recent methodological and instrumental advances in MEKC. Improvements in sensitivity arising from the use of on-line sample concentration (sweeping, stacking, and combination of both protocols) and derivatization (in-capillary reactions and coupling with flow-injection systems) and improvements in resolution obtained by changing the composition of the BGE (e.g., with organic modifiers, ionic liquids, nonionic and zwitterionic surfactants, mixed micelles, and vesicles) or using coated capillaries are discussed in detail. In addition, MS and LIF spectroscopy are examined in relation to their advantages and restrictions as applied to MEKC analysis. Some thoughts on potential future directions are also expressed.

ITP in dynamically double-coated fused-silica capillaries

Bidirectional ITP in fused-silica capillaries double-coated with Polybrene and poly-(vinylsulfonate) is a robust approach for analysis of low-molecular-mass compounds. EOF towards the cathode is strong (mobility >4.0 x 10(-8) m(2)/Vs) within the entire pH range investigated (2.40-8.08), dependent on ionic strength and buffer used and, at constant ionic strength, higher at alkaline pH. Electrokinetic separations and transport in such coated capillaries can be described with a dynamic computer model which permits the combined simulation of electrophoresis and electroosmosis in which the EOF is predicted either with a constant (i.e. pH- and ionic strength-independent) or a pH- and ionic strength-dependent electroosmotic mobility. Detector profiles predicted by computer simulation agree qualitatively well with bidirectional isotachopherograms that are monitored with a setup comprising two axial contactless conductivity detectors and a UV absorbance detector. The varying EOF predicted with a pH- and ionic strength-dependent electroosmotic mobility can be regarded as being realistic.

Determination of inflammatory biomarkers by immunoaffinity capillary electrophoresis

Advances in instrumentation and methodologies are urgently needed to achieve, rapid, simultaneous and sensitive determination of multiple substances found at a wide range of concentrations in biological fluids, tissues and cells. The application of immunoaffinity capillary electrophoresis in life sciences is already having an impact on the quantification of many biomarkers for diagnosis and monitoring the prognosis of diseases. This review explains how immunoaffinity capillary electrophoresis, the combination of highly selective antibody capture agents with the high resolving power of capillary electrophoresis, can provide highly specific assays leading to the selective isolation, concentration, separation and quantification of analytes of interest in complex biological matrices. In addition to a discussion of the technology, some applications of clinical and pharmaceutical relevance will be presented.: