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Synthesis of Periodic Mesoporous Organosilicas and using their Properties for Improving Microextraction Techniques

Karimi Zandian, Faezeh | 2025

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 58180 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib; Balalaie, Saeed
  7. Abstract:
  8. Periodic mesoporous organosilicas (PMOs) are a new class of porous materials with high surface area, ordered structures, and uniform pore sizes. There is a high structural diversity in these materials due to the possibility of choosing different building blocks, functionalization and chemical modification of organic groups. Considering the stated advantages, the synthesis and application of different classes of adsorbents based on periodic mesopore organosilica compounds are the main goals of this thesis. In this regard, in the first research, an attempt was made to use organosilica precursors based on the tyrosine amino acid in the preparation of PMO and then its adsorption capacity towards different classes of pharmaceutical analytes was evaluated. Considering the relatively bulky and flexible structure of the organosilica precursor, an attempt was made to improve the amount of bridging organosilica precursors in the PMO structure by controlling the synthesis conditions. Then, the efficiency of PMO in the field of extraction was evaluated compared to organic-inorganic hybrid organosilica compounds prepared by other methods. For this purpose, the surfaces of the prepared mesoporous silica compounds were chemically modified using non-bridged organosilica precursors within the grafting process. Also, the simultaneous condensation of silica and organosilica precursors was used to prepare the desired hybrid mesopore. After characterizing the prepared adsorbents and optimizing the method, these materials were used in the pipette tip- micro solid phase extraction (PT-µ-SPE) of non-steroidal anti-inflammatory drugs (NSAIDs) in water/wastewaters prior to analysis by high-performance liquid chromatography. Limits of detection and quantification were obtained in the range of 0.1–1.5 and 0.3–5 µg L-1, respectively. The intra-and inter-day precision at 50 and 200 µg L-1 levels are 2.9–7.1% and 3.5–8%, while recoveries are between 84 and 111%. In the second work, considering the confirmation of the more appropriate efficiency of the PMO structures in the first work, an attempt was made to prepare two PMOs with different morphology and structure by controlling the synthesis conditions. For this purpose, different PMOs with UVM-7 and SBA-15 type mesostructures were synthesized using benzimidazole-based organosilica precursor. These two PMOs were used to prepare thin film films with nylon-6 substrate. Then the efficiency of these films were employed in thin film microextraction (TFME) of triazole fungicides prior to gas chromatography-mass spectrometry (GC-MS) analysis. Subsequently, various characterization analyses were carried out to confirm the synthesis of the organosilica precursor along with PMO powders and thin film films. In order to achieve maximum efficiency and sensitivity, the parameters affecting the extraction and desorption processes were investigated and their optimal values were obtained. Finally, the best adsorbent was used for the analytical evaluation of the method. The limits of detection and quantification of the proposed method ranged from 0.02-0.2 and 0.06-0.7 µg L-1, respectively. The relative standard deviation with three replicates for two concentration levels of 20 and 200 ng L-1 was in the range of 3.9-14.1%. The prepared film from UVM-7-based PMO was used to analyze various fruiting vegetable samples. The relative recoveries (85-115%) at two concentration levels of 20 and 200 µg L-1 levels show that this approach works appropriately to detect triazole fungicides in real matrixes
  9. Keywords:
  10. Triazole Fungicides ; Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) ; Pipette Tip Solid Phase Micriextraction ; Thin Film Microextraction ; Liquid Chromatography ; Gas Chromatography ; Periodic Mesoporous Organosilicas (PMOs) ; Santa Barbara Amorphous SBA-15 Nanoporous Silica ; UVM-7 Nanoporous Silica

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