Capillary electrophoresis as a nanoreactor of separation capability: on-capillary reaction catalyzed by transition metal ions

The study of polyoxometalates formation using capillary zone electrophoresis

The formation process of polyoxometalates [PMo12 O40 ](3-) and [PMo12 - x Vx O40 ](-3-x) has been studied in aqueous solutions of 0.1 M malonate buffer at pH 2.8-3.0 using CZE. Two different approaches, pre-capillary and in-capillary, were examined and compared. In precapillary mode, the reaction mixture of the reactants and reaction products was injected into the capillary followed by the separation procedure. In in-capillary mode, the sequential input of the reagents and running electrolyte into the capillary and the species separation occurs simultaneously. The optimal parameters of in-capillary separation were established as functions of applied voltage and the length of the intermediate buffer zone between the reagents in the capillary. As a result the best-compromise conditions for the separation of the mixtures containing the reactants, intermediates, and reaction products, in order to achieve the best efficiency, symmetry, and peak areas, were achieved at -18 kV and the input parameter of 900 mbar·s. It was also shown that in-capillary mode is more informative than pre-capillary mode for studying the complex compound formation process.

Liquid-core waveguide in CE

Liquid-core waveguide (LCW) brings about several advantages in CE. This review discusses some aspects of fundamental and practical importance involved in this method. Sensitivity in absorption and fluorescence detection is in general improved by more than one order of magnitude over usual crossbeam detection arrangements; the improvements come from the long light path in absorption detection and low light scattering in fluorescence detection. Versatile instrumental arrangements are another advantage of LCW in CE, leading to several detection schemes, some of which provide information that is not gained by usual capillary-end crossbeam detection, e.g. whole-capillary imaging, simultaneous monitoring of multicapillary separation, and kinetic evaluation. The high potential and perspectives of LCW in CE are discussed based on the state-of-the-art developments.

Selective Determination of Cadmium(II) from Divalent Metal Ions in Environmental Samples by Capillary Electrophoresis Using In-capillary Complexation with a Lacunary Keggin-type [PW11O39]7- Complex

A novel capillary electrophoretic (CE) method, based on in-capillary complexation with [PW(11)O(39)](7-), was developed for the determination of cadmium(II) in natural water samples. When a sample solution is injected into a capillary containing 0.20 mM [PW(11)O(39)](7-) and 0.10 M malonate buffer (pH 3.0), the ternary Keggin-type complex, [P(Cd(II)W(11))O(39)](5-), which possesses high molar absorbtivities in the UV region, is formed in the capillary, and its migration toward the anode gives a well-defined migration peak in the electropherogram. An advantage of this method is that many divalent metal ions do not interfere. The proposed method was successfully applied to the determination of Cd(II) in environmental samples. The detection limits were 1 x 10(-7) and 5 x 10(-7) M for river-water and seawater samples, respectively (signal-to-noise ratio = 3).

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.

On-column capillary electrophoretic monitoring of rapid reaction kinetics for determination of the antioxidative potential of various bioactive phenols

An on-column capillary electrophoretic procedure for the determination of the antioxidative potential of various bioactive phenols, found in plant, fruit, and vegetable extracts, is described. The assay is based on a rapid mixing of phenols or phenolic extracts before the capillary, followed by pressurized injection of the reaction mixture into the capillary. After incubation of the reaction mixture inside the capillary, high voltage is switched on and separation of reactants and products is performed. Using hydrogen peroxide as a stressor, the kinetics of the oxidation of various bioactive phenols was studied (rutin, chlorogenic acid, quercetin, caffeic acid, gallic acid, and combinations of these) and compared with the oxidation rate of L-ascorbic acid as a reference. The concept was demonstrated for the determination of the antioxidative potential of various polyphenol mixtures and of the methanol extract of the sea buckthorn (Hippophae rhamnoides L.). In most cases quercetin has the highest rate constant of oxidation among the tested phenolic compounds. However, in the mixture L-ascorbic acid/quercetin, the oxidation rate of L-ascorbic acid was enhanced and oxidation of quercetin was strongly inhibited compared with the other combinations of tested polyphenols.

Capillary electrophoresis of inorganic ions: An update

This review as a sequel of three earlier similar reports gives a summary of the progress and significant methodological developments, starting from 2002, in the use of capillary electrophoresis (CE) for inorganic ion analysis. As substantiated by the illustrative number of relevant references, improvements in sensitivity achieved both in and outside a CE system, advances in manipulating the separation selectivity, novel hardware configurations, and system performance innovations are continually being reported over the review period. Specifically viewed are the recent advancements in elemental (bio)speciation analysis, which remains one of the most fertile areas of CE research, as well as in three recently booming research topics: contactless conductivity detection, separations on microchips, and transient isotachophoretic preconcentration. A state-of-the-art picture of technique's potentialities within the field of interest presented here demonstrates that CE has become recognized and is growing in acceptance as a reliable alternative to traditional analytical methods such as high-performance liquid chromatography (HPLC).