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Most sample-enrichment procedures currently available rely on adsorption of the analytes of interest by a suitable adsorbent material. Although good performance can be obtained for many practical problems, in some cases the applicability of adsorptive sample preparation falls short, particularly for the enrichment of polar and/or high-molecular-weight compounds, especially in combination with thermal desorption. Because of the very strong retention of adsorbent materials, undesired effects such as incomplete desorption and artifact formation are observed. Polar solutes are easily adsorbed but readily undergo surface-catalyzed reactions and on desorption yield compounds different than those originally sampled. High-molecular-weight compounds cannot be desorbed because of extremely strong interactions with the adsorbent and their low volatility. To overcome some of these problems sample-preparation techniques based on polydimethylsiloxane sorption have been developed over the past 15 years. In contrast with adsorptive trapping, sorption is based on dissolution of the analytes in a liquid polymeric material. This is a much more inert means of solute retention which overcomes some of the limitations encountered when working with adsorbents. In this contribution, the basic principles of sorption, the different instrumentation used, and applications of the technique will be reviewed. The review covers the sorptive sample-preparation techniques, open-tubular trapping (OTT), solid-phase microextraction (SPME), gum-phase extraction (GPE), equilibrium gum-phase extraction (EGPE), and stir-bar-sorptive extraction (SBSE). Because of the nature of sorptive sample-preparation techniques, which perform particularly well in combination with thermal desorption, this review focuses strongly on gas chromatography as the means of chemical analysis.

This review discusses many different aspects of microcolumn liquid chromatography (LC) and reflects the areas of microcolumn LC research interest over the past decades. A brief theoretical discussion on a number of major issues, such as column characterisation, chromatographic dilution effects and extracolumn band broadening in microcolumn LC is given. Recent progress in column technology and the demands and developments of instrumentation and accessories for microcolumn LC are also reviewed. Besides that, the developments in a large number of established and also more recent detection techniques for microcolumn LC are also discussed. The potential of hyphenation of microcolumn LC with other techniques, more particularly of multidimensional chromatography and microcolumn LC coupled to mass spectrometry is reviewed. Finally, the perspective of microcolumn LC separation methods is stressed by a number of relevant applications.

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The Advanced Oxidation Process pulsed corona discharges have been utilized for the degradation of phenol in aqueous solution. The pulsed positive corona discharges are struck in the ambient gas phase over the solution. Experiments have been performed using both an air and argon atmosphere. Phenol conversion and the production of major oxidation products in the solution have been determined, using ion-exclusion chromatography with UV absorbance and conductivity detectors in series. The corona pulse energy has been measured from voltage and current waveforms using capacitive current correction. Oxidation products are polyhydroxybenzenes and carboxylic acids. Even though phenol conversion efficiencies by pulsed positive corona discharges in air and argon are similar, the degradation pathways are different.