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Development of Novel Microextraction Methods Based on Nanostructured Sorbents

Ayazi Khorehbelagh, Zahra | 2012

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43142 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib
  7. Abstract:
  8. Preparation and application of nanostructured sorbents for microextraction of some environmental pollutants and pesticides are the bases of this research. The first part of thesis deals with carbon nanotubes (CNTs) and their relevant nanocomposites using silica and conductive polymer matrix as extracting media. While, the second part involves the preparation of nanofibers and nanowires and they were applied for extraction of some selected pesticide from aquatic samples.
    In the first work of part one, CNTs chemically bonded on modified gold substrate was used as novel unbreakable solid phase microextraction fiber for isolation of diazinon and fenthion, as model compounds. Parameters influencing the extraction process were optimized. Limits of detection as low as 0.2 ng mL-1 for diazinon, and 0.3 ng mL-1 for fenthion using the time-scheduled selected ion monitoring (SIM) mode, were achieved.
    Next, in order to increase the CNTs effective surface area, a new type of composite material based on sol-gel chemistry was prepared and used as sorbent for needle trap device (NTD) for determination of polycyclic aromatic hydrocarbons (PAHs) as model compounds. Effects of CNTs doping level, surfactant addition and the oxidation duration of CNTs on the extraction efficiency of synthesized composites were investigated. Limits of detection was 0.001 and 0.01 ng mL−1, for different analytes using time-scheduled SIM mode, and the RSD% values (n=3) were all below 11.2% at the 1 ng mL−1 level. The relative recovery percentages obtained for the spiked real water samples were from 74 to 114%.
    Then reinforced polydiphenylamine (PDPA) nanocomposite with CNTs was synthesized and used as an extraction medium for microextraction in packed syringe (MEPS) of selected multiclass pesticides from aquatic environment. It was revealed that when 4 % (w/w) of CNT in the presence of cetyltrimethylammonium bromide (CTAB) is being used, the highest extraction recovery could be achieved. LOD values were in the range of 0.01 to 0.1 ng mL-1 and 0.02 to 0.1 ng mL-1 for distilled water and river water respectively. The method precision with four replicates was in the range of 1.6-14.6 % for distilled water and 1.5-16.2 % for river water, while the linearity of method was in the range of 0.15-100 and 0.5-500 ng mL-1.
    In second part, first polypyrrole/polyamide (PPy/PA)-based nanofiber was prepared using electrospinning method and used as MEPS sorbent to analyze some selected organophosphorous pesticides. For electrospining of PPy/PA-based nanofiber, a homogenous solution containing nylon 6, ferric chloride and the pyrrole monomer was prepared. By applying a voltage of 13 kV between the needle of syringe and an aluminum-foil collector the nanofibers could be formed on the surface of collector. Limits of detection were in the range of 0.04 to 0.1 ng mL-1 and RSD % value with four replicates were in the range of 3.7-11.8 %. The linearity of method was in the range of 0.5-500 ng mL-1. The matrix factors for Zayandeh-roud river water samples were in the range of 0.87-0.98.
    Finally, the polypyrrole (PPy) nanowires network was prepared using soft template technique and used as MEPS sorbent for extraction of triazines. The use of CTAB micelles in this methodology has an important role in the shape of the growing polymer. PPy nanowire network has shown 7-28 times higher extraction capability in comparision with bulk PPy. LOD were in the range of 0.02 to 0.05 ng mL-1. The linearity of method was in the range of 0.5-500 ng mL-1
  9. Keywords:
  10. Carbon Nanotubes ; Nanofiber ; Solid Phase Microextraction ; Needle Trap Extraction ; Neadle Trap ; Gas Chromatography/Mass Spectrometry (GC/MS) ; Microextraction in Packed Syringe (MEPS) ; Carbon Nanotubes Nanocomposites

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