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Gradient Surfaces as New Media in Microextraction Methods

Enteshari Najafabadi, Marzieh | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 52630 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib
  7. Abstract:
  8. The main idea of this thesis is on the preparation and use of gradian surfaces as extractive phase in the development of microextraction methods in non-targeted analysis.In the first research, a structural gradient of nanoclusters of organoclay-Cu(II) on a copper wire were fabricated by bipolar electrofunctionalization. The headspace in-tube microextraction (HS–ITME) technique was used for the extraction of chlorobenzenes (CBs) as model compounds. The limits of detection (LODs) and linear dynamic range (LDR) were obtained in the range of 0.5-10 and 50-10000 μg L-1, respectively and precision of the method was also obtained (RSD%) in the range of 6-10%. The developed method in this study provides the analysis of real samples. The relative recovery for selected pollutants in the water samples were achived in the range of 91-110%.In the second study, a chemical gradient of nanostructure of graphen/polypyrrole on a lead pencil was fabricated by bipolar electrofunctionalization. In order to investigate of gradient sorbent for comprehensive extraction, the chlorobenzenes and chlorophenols (CPs) as nonpolar and polar compounds were selected. To prove the efficiency of chemical gradient sorbent, the graphen (nonpolar) and polypyrrol (polar) were evaluated. Under optimum conditions, the LODs of CBs and CPs (0.1-1 μg L-1), (0.0005-0.03 μg L-1) and precision (5-7%), (8-11%) of the method were obtained, respectively. Finally, the proposed method was used for extraction of the CBs and CPs from water and juice samples with appropriate recovery in the range of 91-107% and 85-112%, respectively.In the third study, the two-component gradient sorbent was fabricated based on sol-gel concept using controlled rate infusion (CRI) method. The aim of this study is to investigate of gradient sorbent in non–targeted analysis. The gradient phase was implemented as a fiber coating in headspace– or immersed–solid phase microextraction of various compounds. Furthermore, uniform single–component fibers from polar and nonpolar coatings were fabricated in order to be compared with the gradient sorbent. Then, the LODs of CBs (0.01-0.5 μg L-1), CPs (0.01-0.05 μg L-1), polycyclic aromatic hydrocarbons (0.01 μg L-1) and volatile organic compounds (0.01-0.1 μg L-1) were obtained.In the fourth study, the two-component gradient sorbent drived base layer was developed for the improvement of gradient sorbents. The base layers from three different sols as nonpolar precursors were used and evaluated. Also, in this work for the improvement of sensitivity and efficiency of extraction, the headspace cooled in–tube microextraction (HS–CITME) method was selected for the determination of volatile organic compounds (VOCs). Figure of merits such as LODs (0.15 μg L-1), LDR (0.5-100 μg L-1) and precision (2-6%) were obtained. Ultimately, the capability of the method was evaluated for determination of VOCs in saliva samples and the acceptable relative recoveries was calculated in the range of 95-108%
  9. Keywords:
  10. Non-Target Analysis ; Gradient Surface ; Bipolar Electrochemical ; Controlled Rate Infusion ; In-Tube Solid Phase Microextraction

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