Samenvatting
Dioxins and dioxin-like compounds are some of the most toxic man-made compounds known. Their hydrophobicity causes them to accumulate in river sediment and in the sludge of waste water treatment plants (WWTPs). It is important to verify that the concentration of these compounds is below an acceptable level of contamination if the sludge is to be used as fertilizers on fields. Gas chromatography in combination with high resolution mass spectrometry (GC-HRMS) analysis is the standard reference method to determine the concentration of dioxins, but it is both time consuming and expensive. GC-HRMS also does not provide information of the toxicity of the sample directly. This information is calculated by means of Toxic Equivalency Factors (TEFs) such that a Toxic Equivalent (TEQ) is estimated. To overcome these problems, a bioassay called Chemically Activated Luciferase Expression(CALUX) has been developed which makes use of genetically modified mouse hepatoma cells. It provides a measure of the toxicity of a sample as a Biological Equivalent (BEQ). In this thesis a program is developed to analyze raw CALUX data in a consistent manner after which some methodologies for improving the use of this bioassay are investigated. First, a more recently developed cell line H1L7.5c1 is validated against the already much in use cell line H1L6.1c3. It is found that both cell lines give comparable results with the same precision,
but that less sample volume is necessary for the newer cell line thus effectively lowering the detection limit of the bioassay. A new sample preparation procedure is also proposed by adding an extra clean-up column that contains activated copper to remove the sulfur from the sample. This way, the same preparation procedure can be used for both CALUX and GCHRMS analysis, facilitating the comparison between the results of both analytical methods.
Lastly, two different calculation methods to calculate the BEQ from the raw data as obtained by CALUX analysis are compared to each other. It is shown that the slope ratio after Box-Cox transformation calculation provides a good alternative to the more frequently used effective concentration ratio obtained by fitting the four parameter Hill equation as less data points are necessary for calculating the BEQ while at the same time a much higher precision on the result can be obtained.
| Datum prijs | 2010 |
|---|---|
| Originele taal | English |
| Begeleider | Marc Elskens (Promotor), David Scott Baston (Co-promotor) & Kersten Van Langenhove (Advisor) |
Citeer dit
- Standard