Determination of lactate or oxalate using injected lactate oxidase and peroxidase by capillary electrophoresis with UV detection

Enzymatic in-capillary derivatization for glucose determination by electrophoresis with spectrophotometric detection

The following paper compares several procedures of in-capillary bienzymatic derivatization with regard to glucose determination with the use of glucose oxidase and horseradish peroxidase. The procedures discussed below include continuous contact in the capillary, plug-plug injection, and sequential injection with incubation in the capillary inlet. The reaction of hydrogen peroxide catalyzed by peroxidase was performed using two different substrates. The best results were achieved for nicotinamide adenine dinucleotide, reduced disodium salt (NADH) acting both as a chromogenic reagent and a substrate for peroxidase, while the method employed was sequential injection and incubation at the capillary inlet. The LOD was estimated to be 25 nM with a linear response up to 0.1 microM.

Development of off-line and on-line capillary electrophoresis methods for the screening and characterization of adenosine kinase inhibitors and substrates

Fast and convenient CE assays were developed for the screening of adenosine kinase (AK) inhibitors and substrates. In the first method, the enzymatic reaction was performed in a test tube and the samples were subsequently injected into the capillary by pressure and detected by their UV absorbance at 260 nm. An MEKC method using borate buffer (pH 9.5) containing 100 mM SDS (method A) was suitable for separating alternative substrates (nucleosides). For the CE determination of AMP formed as a product of the AK reaction, a phosphate buffer (pH 7.5 or 8.5) was used and a constant current (95 microA) was applied (method B). The methods employing a fused-silica capillary and normal polarity mode provided good resolution of substrates and products of the enzymatic reaction and a short analysis time of less than 10 min. To further optimize and miniaturize the AK assays, the enzymatic reaction was performed directly in the capillary, prior to separation and quantitation of the product employing electrophoretically mediated microanalysis (EMMA, method C). After hydrodynamic injection of a plug of reaction buffer (20 mM Tris-HCl, 0.2 mM MgCl2, pH 7.4), followed by a plug containing the enzyme, and subsequent injection of a plug of reaction buffer containing 1 mM ATP, 100 microM adenosine, and 20 microM UMP as an internal standard (I.S.), as well as various concentrations of an inhibitor, the reaction was initiated by the application of 5 kV separation voltage (negative polarity) for 0.20 min to let the plugs interpenetrate. The voltage was turned off for 5 min (zero-potential amplification) and again turned on at a constant current of -60 microA to elute the products within 7 min. The method employing a polyacrylamide-coated capillary of 20 cm effective length and reverse polarity mode provided good resolution of substrates and products. Dose-response curves and calculated K(i) values for standard antagonists obtained by CE were in excellent agreement with data obtained by the standard radioactive assay.

Advances in capillary electrophoretically mediated microanalysis: An update

This review, as a continuation of an earlier report, gives an overview of recent developments, over the period from 2003 until now, in the use of capillary electrophoretic techniques for the in-line study of enzymatic reactions, derivatization, and chemical reactions. The article is divided into two parts: (i) in-line enzymatic reactions and (ii) in-line derivatization and chemical reactions. The first part introduces electrophoretically mediated microanalysis (EMMA) and discusses and illustrates the different modes of EMMA. A literature overview on enzymatic reactions is provided. The second part starts with an introduction of the procedures and the nomenclature used in the area of in-line derivatization and chemical reactions based on EMMA. Reported derivatization and chemical reaction procedures are discussed and summarized.

Analysis of carboxylic acids in biological fluids by capillary electrophoresis

This review article addresses the different capillary electrophoretic methods that are being used for the study of both short-chain organic acids (including anionic catecholamine metabolites) and fatty acids in biological samples. This work intends to provide an updated overview (including works published until November 2004) on the recent methodological developments and applications of such procedures together with their main advantages and drawbacks. Moreover, the usefulness of CE analysis of organic acids to study and/or monitor different diseases such as diabetes, new-borns diseases or metabolism disorders is examined. The use of microchip devices and CE-MS couplings for organic acid analysis is also discussed.