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Development of Microextraction Methods
for the Trace Determination of Organic Compounds in Biological and Environmental Media

Khalilian, Faezeh | 2009

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 39831 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib
  7. Abstract:
  8. The approach of this thesis is to develop and simplify robust microextraction techniques and apply these developed methods to real samples and complex matrices. Firstly, a modified solvent microextraction with back extraction method (SME/BE) combined with high performance liquid chromatography and fluorescence detection (HPLC-FD) was developed for the determination of citalopram in human plasma. Extraction process was performed in a home-made total glass vial without using a teflon ring, usually employed in SME/BE. The evaluation results demonstrated that the calibration curve showed linearity in the range of 1.0–130.0 ng/mL which covers therapeutic window and even lower amounts which is important in pharmacokinetic studies. Limits of detection and quantification, based on a signal to noise ratio (S/N) of 3 and 10, were 0.3 and 0.8 ngmL−1, respectively.The method was succeessfully applied for the determination of citalopram in plasma samples after oral administration of 40mg single dose of citalopram which shown feasibility of method in real sample analysis. In the next work, an electro membrane extraction (EME) methodology was firstly utilized to study the isolation of some environmentally important pollutants, chlorophenols, from aquatic media based upon the electrokinetic migration process. The analytes were transported by application of 10 V electrical potential difference over 1-octanol as supported liquid membrane (SLM). Since the developed method showed a rather high degree of selectivity toward pentachlorophenol (PCP), validation of the method was performed using this compound. An enrichment factor of 23 along with acceptable sample clean-up was obtained for PCP. The calibration curve showed linearity in the range of 0.5–1000 ng/mL with a coefficient of estimation corresponding to 0.999. Limits of detection and quantification, based on signal-to-noise ratios of 3 and 10, were 0.1 and 0.4 ng/mL, respectively. The method was also applied to the extraction of this contaminant from sea water and an acceptable relative recovery was achieved. This work was performed during sabbatical leave in National University of Singapore. A micro-solid phase extraction (µ-SPE) technique, based on conductive polymers, was developed by fabricating a rather small package including a polypropylene membrane shield containing the appropriate sorbent. The package was used for the extraction of some triazine herbicides from aqueous samples. Solvent desorption was subsequently performed in a micro-vial and an aliquot of extractant was injected into gas chromatography–mass spectrometry (GC–MS). Various sorbents including aniline-ortho phenylene diamine co-polymer (PANI-OPD), newly synthesized, polypyrrole (PPy), multi-wall carbon nanotube (MW-CNT), C18 and charcoal were examined as extracting media. Among them, conductive polymers exhibited better performance. The detection limits of the method under optimized conditions were in the range of 0.01–0.04 ng/mL. The relative standard deviations (RSD) at a concentration level of 0.1 ng/mL were obtained between 4.46 and 9.34% (n = 5). The calibration curves of analytes showed linearity in the range of 0.05–10 ng/mL. The whole procedure showed to be conveniently applicable and unlike the other major methods, little problems were no longer interfering the extraction process. The developed method is rather convenient and quite easy to manipulate.
  9. Keywords:
  10. High Performance Liquid Chromatography ; Gas Chromatography/Mass Spectrometry (GC/MS) ; Chlorophenols ; Solid Phase Microextraction ; Triazines Herbicides ; Water Analysis ; Environmental Analysis ; Solvent Microextraction with Back Extraction ; Electromembrane Extraction ; Citalopram

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