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Isolating organic micropollutants from water samples by means of XAD resins and supercritical fluid extraction

Het isoleren van organische microverontreinigingen uit watermonsters m.b.v. XAD harsen en super-kritische fase extractie

Synopsis

A better understanding of ecosystem perturbation requires the ability to measure the ecotoxicological effects of a complex variety of chemicals and to separate toxic stress on the ecosystem from other stress factors. This report describes an experimental approach which can be applied to surface water. A procedure was assessed to obtain an aqueous concentrate of organic micro-pollutants from a (surrogate) surface water sample. The method relies on the application of macro-reticular resins, which are usually denoted as XAD, to extract organic micro-pollutants from water and subsequent elution with supercritical carbon dioxide (SFE) to release the toxicants from the XAD and to transfer them to a small volume of water, without making use of an organic solvent. Surrogate water samples containing test mixtures of chemicals that cover a wide variety of physico-chemical properties, were submitted to the procedure. The XAD/SFE combination produces an extract that is directly compatible to bio-assays. This has the advantage over more conventional procedures based on the use of an organic solvent which has to be removed to a specified level to obtain a water sample that is compatible to bio-assays. There is a considerable loss of (semi)-volatile chemicals if the organic solvent has to be separated from the extract. For these micropollutants the XAD/SFE procedure proved more efficient than a method developed previously, based on acetone as elution solvent. The latter approach, however, performs much better if more polar chemicals are concerned. Recommendations are made to apply a two-step supercritical fluid extraction: one exclusively based on supercritical CO2 to collect the apolar substances and the second with a modifier added to the supercritical fluid to desorp the more polar chemicals.
 

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