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Membrane extraction in environmental chemical analysis

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Author

Summary, in English

Membrane extraction techniques permit the application of classical liquid-liquid extraction (LLE) chemistry to instrumental and automated operation. Various shortcomings of LLE are overcome by membrane extraction techniques as they use none or very little organic solvents, high enrichment factors can be obtained and there are no problems with emulsions. A three phase SLM system (aq/org/aq), where analytes are extracted from the aqueous sample into an organic liquid, immobilized in a porous hydrophobic membrane support, and further to a second aqueous phase, is suitable for the extraction of polar compounds (acidic or basic, charged, metals, etc.) and it is compatible with reversed phase HPLC. A two-phase system (aq/org) where analytes are extracted into an organic solvent separated from the aqueous sample by a hydrophobic porous membrane is suitable for more hydrophobic analytes and is compatible with gas chromatography. The experimental format can be based on either flat membranes and on hollow fibre membranes in various ways. Using hollow fibers, it is possible to perform extractions for sample clean-up and enrichment with very cheap and simple equipment, leading to high enrichment factors (easily thousands of times) for ultra trace analysis. Membrane extraction can be a basis for environmental field sampling. Such sampling can be performed in two different regimes, with different purposes. One aim is to attempt a complete extraction of the analytes in a sample, in order to determine the total concentration of these analytes. This is similar to what is attempted with classical techniques such as LLS, and SPE (solid phase extraction). An alternative and complementary way of working is to attempt equilibrium between the sample and the sampler, with minimum disturbance of the sample. These are the principles of "equilibrium extraction through membranes" (ESTM) as recently was developed. This technique leads to the determination of the freely dissolved concentration lie not complexated or otherwise bound fraction) of the analyte. This is related to the bioavailability, fugacity and chemical potential of a pollutant in the sample and is therefore significant for the evaluation of S toxicity and transport processes of the pollutant in the environment, both for polar organic compounds, and for metal ions.

Publishing year

2007

Language

English

Pages

37-42

Publication/Series

Proceedings of ECOpole

Volume

1

Issue

1-2

Document type

Conference paper

Publisher

Opole University

Topic

  • Analytical Chemistry

Keywords

  • speciation
  • hollow fiber
  • sampling
  • sample preparation
  • extraction
  • enrichment
  • free fraction

Conference name

16th Central European Conference ECOpole 2007

Conference date

2007-10-18 - 2007-10-20

Conference place

Duszniki Zdroj, Poland

Status

Published

ISBN/ISSN/Other

  • ISSN: 1898-617X