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High-Throughput Determination of Pesticide Residues by Solid-Phase Microextraction and Micro-Solid Phase Extraction on 96-Well Plate

Eshaghi, Ali | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 44919 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Bagheri, Habib; Es-haghi, Ali
  7. Abstract:
  8. Novel high-throughput device and their applications as the microextraction systems for pesticide multiresidue determination is the centre of this research. 96 extracting unit based on solid phase microextraction and micro-Solid phase extraction were constructed and applied for high-throughput extraction.
    In the first work, a high-throughput SPME on 96-well plate together with gas chromatography-mass spectrometry was developed for the determination of pesticide residues in cucumber samples. A home-made Teflon block consisting ninety-six holes was constructed to 96 SPME fibers being positioned in. SPME fibers consisted of stainless steel rods with a 1.0 cm polydimethylsiloxane tubing covered on the last end length of them. The performances of the SPME fibers, such as intra and inter-fibers reproducibility, were evaluated and the results showed a good similarity in extraction yields. 1 mL of the aquatic supernatant of the cucumber samples was transferred into the 96-well plate and the array of SPME fibers was applied for the extraction of selected pesticides. The important parameters influencing the whole extraction including, organic solvent percent, salt addition, dilution factor, stirring rate and extraction time were optimized. The inter and intra-day RSD% were found to be less than 15.4%. Limits of detection and limits of quantification were below 60 and 180 µg kg-1, respectively. The coefficient of determination was satisfactory (r2 > 0.99) for all the studied analytes. The developed method was successfully applied to the monitoring of several samples gathered from local markets.
    In the second work, a novel high-throughput device based on 96-µ-SPE system was constructed for multiresidue determination of nine pesticides in aquatic samples. The extraction module consisted of 96 pieces of 1×3 cm of cylindrically shaped stainless steel meshes. The prepared meshes were fixed in a home-made polytetrafluoroethylene-based constructed ninety-six holes block for possible simultaneous immersion of meshes into the center of individual wells. Dodecyl methacrylate and ethylene glycol dimethacrylate was copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless steel meshes as extracting medium. A volume of 1 mL of the aquatic sample was transferred into the 96-well plate and the 96-µ-SPE device was applied for the extraction of the selected pesticides. Subsequently, the extracted analytes were analyzed by GC-MS. Influential parameters such as polymer synthesis conditions, sorbent-to-sorbent reproducibility, ionic strength and extraction time were optimized. Intra and inter-sorbent reproducibility on 96-µ-SPE device were evaluated and results revealed that extraction yields are rather similar. LODs were below 4 µg L-1 and the coefficient of determination was satisfactory (r2 > 0.99) for all the studied analytes. The developed method was successfully applied to the extraction and determination of the selected pesticides in surface water samples.
    In the third work, the constructed high-throughput 96-µ-SPE device was successfully applied for determination of five pesticides in apple samples. Butyl methacrylate and ethylene glycol dimethacrylate was copolymerized as a monolithic polymer and after placing in 96-µ-SPE device meshes, used as extracting medium. Microwave assisted extraction was applied for extraction of selected pesticides from spiked apple samples. 1 mL of the achieved aquatic supernatant of the apple samples was transferred into the 96-well plate and the 96-µ-SPE device was applied for the extraction of selected pesticides. Finally, GC-MS was used for detection and determination of extracted analytes. The important parameters influencing the whole extraction including: MAE time, co-solvent addition, salt addition, stirring rate and extraction time were optimized. The inter and intra-day RSD% were found to be less than 16.3%. LODs and LOQs were below 40 and 120 µg kg-1, respectively. The developed method was successfully applied to the monitoring of several samples gathered from local markets.
  9. Keywords:
  10. 96 Well-Plate ; High-Throughput Determination ; Polydimethylsiloxane ; Monolithic Polymer ; Pesticides Residue ; Solid Phase Microextraction ; Solid Phase Extraction

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