Membrane Dialysis Extraction (MDE): A Novel Approach for Extracting Toxicologically Relevant Hydrophobic Organic Compounds from Soils and Sediments for Assessment in Biotests |
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Authors: | Thomas-B Seiler Andrew Rastall Erik Leist Lothar Erdinger Thomas Braunbeck Henner Hollert |
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Institution: | 6085. Thomas-B. Seiler
Department of Zoology
Aquatic Ecology and Toxicology Group
Morphology and Ecology Section
University of Heidelberg
Im Neuenheimer Feld 230
69120 Heidelberg
DEUTSCHLAND, ?, ?, 5401. Andrew Rastall
Institute of Hygiene and Medical Microbiology
University of Heidelberg
Im Neuenheimer Feld 324
D-69120 Heidelberg
Germany, ?, ?, 4254. Erik Leist
AG Aquatische ?kologie und Toxikologie
Zoologisches Institut der Universit?t Heidelberg
INF 230
69120 Heidelberg, ?, ?, 4156. Dr. Lothar Erdinger
University of Heidelberg
Institute for Hygiene
Department for Hygiene and Medical Microbiology
Im Neuenheimer Feld 324
D-69120 Heidelberg
Germany, ?, ?, 4152. Prof. Dr. Thomas Braunbeck
Aquatic Ecology and Toxicology Unit
Department of Zoology
University of Heidelberg
Im Neuenheimer Feld 230
D-69120 Heidelberg
Germany, ?, ?, 3867. Dr. Henner Hollert
Heidelberger Institut für Zoologie (HIZ)
Universit?t Heidelberg
Im Neuenheimer Feld 230
69120 Heidelberg
Germany, ?, ?,
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Abstract: | Goal, Scope and Background Organic solvents are routinely used to extract toxicants from polluted soils and sediments prior to chemical analysis or
bioassay. Conventional extraction methods often require the use of heated organic solvents, in some cases under high pressure.
These conditions can result in loss of volatile compounds from the sample and the degradation of thermally labile target
analytes. Moreover, extracts of soils and sediments also frequently contain substantial quantities of organic macromolecules
which can act as sorbing phases for target analytes and in doing so interfere with both chemical analysis and bioassays.
Membrane dialysis extraction (MDE) is described as a simple, passive extraction method for selectively extracting toxicologically
relevant hydrophobic organic compounds (HOCs) from polluted soils and sediments and anaylzed for its applicability in ecotoxicological
investigations.
Methods Toxicologically relevant hydrophobic organic compounds were extracted from wet and dry sediments by sealing replicate samples
in individual lengths of pre-cleaned low-density polyethylene (LD-PE) tubing and then dialysing in n-hexane. The efficacy
of the MDE method for use in ecotoxicological investigations was assessed by testing the concentrated extracts in the neutral
red assay for acute cytotoxicity, in the EROD assay for the presence of dioxin-like compounds and in the Danio rerio fish
egg assay for embryotoxic and teratogenic effects. Conditions of the sediment sample (with or without water content), dialysis
membrane length and duration of dialysis were analyzed with respect to their impact on three endpoints. Results of the MDE
investigations were compared to data obtained in samples prepared using conventional Soxhlet extraction.
Results and Discussion The membrane dialysis extraction was found to be at least as efficient as Soxhlet methodology to extract toxicologically
relevant HOCs from sediment samples. In most cases, MDE-derived extracts showed a higher toxicological potential than the
Soxhlet extracts. Lack of any significant effects in any MDE controls indicated these differences were not caused by contamination
of the LD-PE membrane used. The elevated toxicological potential of MDE extracts is most likely the result of enhanced bioavailability
of toxic compounds in consequence of lower amounts of organic macromolecules (i.e. sorbing phases) in the MDE extracts.
This effect is probably the result of a size-selective restriction by the LD-PE membrane.
Conclusion Membrane dialysis extraction was found to be a simple, efficient and cost-effective method for the extraction of sediment
samples. MDE can be used to extract toxicologically relevant hydrophobic organic compounds from both wet and dry sediments
without the risk of loosing volatile and thermally labile target analytes. The size-selectivity of the LD-PE membrane also
appears to have the capacity to increase the bioavailablity of potential target analytes in the resulting extracts by retaining
much of the organic macromolecules present in the sample. Thus, results suggest that MDE may be particularly useful for
the extraction of toxicologically relevant hydrophobic organic compounds from soils and sediments for bioassays and other
ecotoxicological investigations.
Recommendation and Perspective Further validation of MDE has been initiated and the applicability of the methodology to other sample types will be investigated.
Of particular interest is the potential application of MDE to recover hydrophobic target analytes from biological samples
such as muscle, other soft tissues and blood. |
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Keywords: | cytotoxicity Danio rerio EROD humic substances membrane dialysis extraction (MDE) sediment toxicity soil toxicity Soxhlet |
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