Post-graduate theses
Current Record: 591 of 642
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| Identifier |
uch.chemistry.msc//2001tsogka |
| Title |
Βελτιστοποίηση της συνδυαστικής τεχνικής αέριας χρωματογραφίας υψηλής ανάλυσης με δίδυμη φασματομετρία μάζας και εφαρμογή της για την ανάλυση διοξινών και φουρανιών σε αέρια δείγματα |
| Creator |
Tsogka, Athanasia
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| Abstract |
Polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs) are two classes of compounds which are of environmental concern because of the high toxicity of those isomers with 2,3,7,8-tetrachloror substitution. They are produced in small quantities from a large number of diverse man-maid and natural sources. These chemicals contaminate most areas of the world and accumulate in the food web. The major source of nonoccupational exposures to humans from PCDDs/PCDFs is animal food. In view of adverse health effects and widespread and persistent presence of PCDDs/PCDFs in the environment, these compounds are monitored in air, rain, effluents, soil and biota matrices. Measuring PCDDs/PCDFs background concentrations requires methods that provide extremely high sensitivity (low picogram to low femptogram range). Specificity is obtained through extensive purification followed by determination with a GC/MS technique. Because of the very low concentrations of PCDDs/PCDFs in air, high resolution mass spectrometry in combination with high resolution gas chromatography was the method of choice. These instrument are very expensive to purchase and to maintain, so the aim of this study was to establish a method which delivers comparable results by using the more economic ion trap mass spectrometers (ITMS). The advantages of this method in comparison to quantrapole instruments, which are often used to determine these substances in other matrices, are the increase in sensitivity and the greater selectivity. They are reached by the typical MS/MS (tandem mass spectrometry) four-step process involving ionization (Electron Impact), parent isolation, collision induced dissociation (CID) and mass analysis of daughter ions. However, in tandem mass spectrometry a set of parameters has to be optimized in order to attain the required sensitivity. Five parameters were varied, including ion source temperature, isolation time, excitation time, excitation voltage and q value. By this optimization a limit of detection of 125 fg/μl was obtained. Tandem mass spectrometry by ion trap mass spectrometers provides high sensitivity and selectivity and ensures reliable results for analysis of low contaminated samples like air samples. So, after the optimization studies, 10 samples of particulate and gas phase from the atmosphere of several areas of Athens and Crete were analyzed.
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| Issue date |
2001-06-01 |
| Date available |
2001-07-20 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Chemistry--Post-graduate theses
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Type of Work--Post-graduate theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/b/1/c/metadata-dlib-2001tsogka.tkl
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| Views |
179 |
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