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- Type of Document: Ph.D. Dissertation
- Language: Farsi
- Document No: 51603 (03)
- University: Sharif University of Technology
- Department: Chemistry
- Advisor(s): Bagheri, Habib; Zamani, Cyrus
- Abstract:
- An inexpensive microfluidic chip–silicon rubber–based system was fabricated. A triangle–shaped micro canal with a 135 µm width and 234 µm depth was grooved by laser ablation technique. The groove was sealed by a thin glass cover while two pieces of stainless steel tubings were connected to each side of canal. Then, a polyaniline film with a thickness of 17±1 µm was synthesized on the walls of the canal by chemical oxidation using a syringe pump to deliver the relevant reagents. The microfluidic system was eventually connected to gas chromatography-mass spectrometry. To evaluate the capability of the constructed fluidic system, it was implemented to the analysis of sub–mL volumes of environmental samples spiked with the trace amounts of some pesticides residues. The developed hyphenated system was used to for the determination of triazines while only 500 µL sample was sufficient to obtain the limits of detection ranged from 0.2 to 0.5 ng mL-1. In addition, the influential extraction parameters such as sample volume, flow rate and sample pH were optimized. Under the optimized condition, the relative standard deviation values for double distillated water sample spiked with the selected triazines at 250 ng mL-1 were 6.5–12.5% (n=3). Then , a silicon wafer–based microchip possessing a 50–cm microchannel with the dimensions of 120 and 60 µm was manufactured by chemical etching technique. Subsequently, the inner surface of the microchannel was coated with a primary layer of gold nanoparticles synthesized by galvanic displacement. Then a self–assembled monolayer of 3–mercaptopropyltriethoxysilane was immobilized on the first layer. Eventually, a polydimethylsiloxane film with a thickness of 16±1 µm was formed on the walls of the microchannel by means of sol–gel method. Field emission scanning electron microscopy and atomic force microscopy were extensively employed to investigate the status of both microchip fabrication and the multilayer coating steps. The entire surface of the prepared microchip was sealed by thin borosilicate glass plate. Furthermore, a ceramic plate with a screen–printed platinum heater was attached to the back of the silicon wafer microchip in order to heat up the microchannel during thermal desorption process. Additionally, a six-port injection valve was utilized between the microchip and nitrogen source allowing the stream of sample and heated gas being introduced into the microchannel. By adopting this extraordinary strategy, the so–called lab–on–a–valve endowed with the feature of direct conjunction with the injection port of the gas chromatography which so far been rarely considered. This lab–on–a–valve system was successfully exploited to evaluate its extraction/desorption capability in analysis of broad categories of model compounds.
- Keywords:
- Lab-on-a-Valve ; Microfluidic Devices ; Environmental Pollutant ; Gas Chromatography ; Solid Phase Extraction ; Sol-Gel Method ; Multi-Layer Coating
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