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Fiedziukiewicz, M, 2024. Stable isotope analysis of anthropogenic compounds in aquatic systems. PhD, Nottingham Trent University.
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Abstract
Isotopic fractionation can be very specific, based on initial isotopic composition, the type of reaction, and ambient conditions. Therefore, stable isotope techniques are frequently applied to environmental studies. However, the compounds of interest in the environment are often in trace concentrations. Any extraction steps following can be lengthy, making routine analysis impractical. Wide screening of compounds has not been explored either.
A focus was made on phthalates as a group of common pollutants with negative health effects not only to the environment but also humans as well. DEHP δ 13C value results ranged between -28.8 ‰ to -27.1 ‰ and measured at 0.14 to 0.22 µg L -1 in surface waters. The quantification was done through the combined and simultaneous measurement using GC-C IRMS. This makes it the first report of a compound specific isotope analysis at trace levels in surface water combined with quantification of that compound.
By examining the ratios of individual datapoints from individual chromatogram channels (44 m/z, 45 m/z, and 46 m/z) allows to verify if there is any interference in the underlying signal. Such practice expands the application scope of compound specific isotope analysis to all heavily gradient programmes, elevated baselines, and closely eluting peaks which is currently limited to fully separated peaks with stable baseline only. The above approach was applied to the surface water samples and published in an international journal in 2021.
The extent of chromatographic isotope effects was indirectly correlated with the molecule size, something that has not been done before. In addition, a little unknown isotope effect on chromatographic peak width was better defined and quantified. DEP and DBP standards had almost up to 6% difference between isotope peaks widths at different GC programme conditions. Those were linked to the structural differences between heavy and light isotopologue.
Results demonstrated that it is possible to perform a trace quantitative analysis, and measure the δ13C value of the selected compound simultaneously using only the GC-C-IRMS. Typical approach can include the ratio of the 45 m/z and 44 m/z. The new approach is compensated for oxygen. An integration of chromatogram signals with common slope threshold for peak detection was shown that it might be insufficient due to chromatographic effects introduced. Depending on the approach taken to the integration of the same peak shifted the δ13C by over 1.2 ‰.
| Item Type: | Thesis |
|---|---|
| Creators: | Fiedziukiewicz, M. |
| Contributors: | Name Role NTU ID ORCID |
| Date: | September 2024 |
| Rights: | The copyright in this work is held by the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed to the author. |
| Divisions: | Schools > School of Science and Technology |
| Record created by: | Jeremy Silvester |
| Date Added: | 10 Jul 2025 15:48 |
| Last Modified: | 10 Jul 2025 15:50 |
| URI: | https://irep.ntu.ac.uk/id/eprint/53930 |
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