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Superhydrophobic Materials as Nanosorbents for Extraction Methodologies

Baktash, Mohammad Yahya | 2018

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50817 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry Analytical
  6. Advisor(s): Bagheri, Habib
  7. Abstract:
  8. In the first work, a superhydrophobic polystyrene hollow fiber (PS–HF) was synthesized by electrospinning and used in microextraction of trazine herbicides from aquatic media followed by gas chromatography mass spectrometric (GC–MS) determination. Effects of different parameters influencing the extraction efficiency including the solvent extraction and its amount, the desorbing solvent and its amount, extraction time and ionic strength were optimized. The characteristic properties of the hollow fiber were studied by scanning electron microscopy (SEM). The limits of detection and quantification of the method under optimized condition were 2 and 6 ng L-1, respectively. The relative standard deviations (RSD) at a concentration level of 100 ng L-1 were obtained between 2 and 6% (n = 3). The calibration curves of triazins showed linearity from 6 to 300 ng L-1. The developed method was successfully implemented to the extraction of triazines from real water samples and relative recoveries were between 76 and 107%.In the second work, we synthesized a superhydrophobic silica aerogel by sol–gel method which subsequently implemented for needle trap microextraction of chlorobenzenes. The superhydrophobic property effects of the aerogel–based sorbent was investigated by altering the trimethyl orthosilicate / methyltrimethoxysilane ratio for each synthesis procedure. The observed contact angle approved the superhydrophobic properties of the synthesized silica aerogel. The applicability of this sorbent was examined by developing a needle trap extraction method for isolation of chlorobenzenes and their gas chromatography–mass spectrometric detection in aqueous samples. The limits of detection and quantification of the method under the optimized conditions were 1.1 and 4 ng L-1, respectively. The relative standard deviations (RSD%) at a concentration level of 10 ng L-1 were between 4 and 8% (n=3). The calibration curves of chlorobenzenes showed linearity from 2 to100 ng L-1. The proposed method was successfully applied to the analysis of real water samples and the relative recoveries were between 88 and 109%.Then, an attempt was made toward synthesizing a sol–gel–based silica aerogel and its subsequent coating on a copper wire by phase separation of polystyrene. Adaption of this new approach enabled us to coat the metallic wire with powder materials. The use of this method for coating, led to the formation of a porous and thick structure of silica aerogel. The coated wire was placed in a needle and used as the sorbent for in–tube solid phase microextraction of chlorobenzenes. The superhydrophobicity of sorbent on extraction efficiency was investigated by the use of different ratio of trimethyl orthosilicate / methyltrimethoxysilane. The surface coated with the prepared silica aerogel by the phase separation of polystyrene showed high contact angle, approving the desired superhydrophobic properties. The limits of detection and quantification of the method under the optimized condition were 0.1–1.2 and 0.4–4.1 ng L-1, respectively. The relative standard deviations at a concentration level of 10 ng L-1 were between 4 and 10 % (n = 3). The calibration curves of CBs showed linearity from 1 to100 ng L-1. Eventually, the method was successfully applied to the extraction of model compounds from real water samples and relative recoveries varied from 88 to 115%.
    Finally, a new approach for extraction and determination of polycyclic aromatic hydrocarbons from water samples was developed by implementing a superhydrophobic substrate and consuming the least amount of solvent. This version of solvent–supported microextraction enabled us to perform the procedure in the immersion mode with the slightest troubles arising from water leakage into the gas chromatography. The superhydrophobic property leads to the fixation of extracting solvent on the substrate surface during water sampling. The limits of detection and quantification of the method under the optimized conditions were 0.01-0.11 and 0.03-1.01 µg L-1, respectively. The relative standard deviations at the concentration level of 20 µg L-1 were between 3 and 14% (n=3). The linearity of calibration curves ranged from 0.03 to 60 µg L-1. The implementation of the solvent-supported method to the analysis of real water samples was quite successful and the relative recoveries were between 88 and 107%
  9. Keywords:
  10. Silica Nanoparticles ; Electrospinning ; Solid Phase Microextraction ; Superhydrophobic Surfaces ; Aerogel Synthesis ; Gas Chromatography/Mass Spectrometry (GC/MS)

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