Research And Application Of Organic Hybrid Silica Aerogel Coated Solid-Phase Microextraction Fiber

Solid-phase microextraction(SPME)is a solvent-free sample pretreatment technique that emerged in the 1990 s.It mainly relies on the distribution equilibrium coefficient of analytes between the sample matrix and the extraction coating to achieve analytes separation and enrichment.SPME has been applied in many fields such as environmental analysis,food testing,pharmaceutical detection,biological analysis and pesticide residue detection because of its simplicity,rapid and efficient superiority,and pollution-free.The extraction coating is the core part of SPME.The properties of the coating material determine the extraction efficiency.In order to develop SPME fibers with excellent extraction performance and good stability,various materials have been used to prepare SPME coating.Among them,the most popular coating materials include carbon materials,metal organic frameworks,nanomaterials and polymers,which have both the excellent extraction performance and high specific surface area.The high specific surface area provides more adsorption sites,which effectively increases the enrichment ability.Aerogel has an ultra-high specific surface area and is lightest solid material.It has been applied in adsorption,energy storage,thermal insulation and aerospace.Silica aerogel as a common inorganic aerogel emerged the earliest and most widely used.It is made of silica colloidal particles and has a high specific surface area.However,silica aerogel has obvious disadvantages like high brittleness and poor strength.The strong polarity makes it extremely easy to absorb water and greatly decreases the specific surface area,which seriously hinders the development and application of silica aerogel.In order to issue these problems,the modification methods mainly include physical doping of polymers or nanomaterials,chemical bonding of organosilanes,surface or internal bonding polymers.Previous studies indicated that silica aerogel had good extraction and adsorption potential.In order to apply silica aerogel to SPME,it is necessary to improve mechanical strength and polarity by means of organic hybridization.Moreover,the introduction of functionalized groups can enhance its extraction performance.Based on these considerations,this thesis designed and synthesized organic functional molecules with terminal group-Si-OCH3,organosilane coupling agent(tris-[3-(trimethoxysilyl)propyl]amine)and ion liquid modified silane coupling agent(1,1'-bis[3-(trimethoxysilyl)propyl]-4,4'-bipyridyl dibromide),separately mixed with tetraethyl orthosilicate as the co-precursor.Two new organic hybrid silica aerogels were synthesized by simultaneous hydrolysis,and they were used as SPME coatings on the stainless steel wire to produce SPME fibers.The self-assembled SPME device with the fiber was coupled with gas chromatography to establish an analytical method and it was applied to the highly sensitive analysis and detection of polycyclic aromatic hydrocarbons(PAHs)in environmental water samples.The main research contents include two parts.1.A novel silane coupling agent tris-[3-(trimethoxysilyl)propyl]amine was synthesized by the reaction between 3-aminopropyltrimethoxysilane and 3-chloropropyltrimethoxysilane.A novel organic-inorganic hybrid aerogel was prepared by co-hydrolysis of tris-[3-(trimethoxysilyl)propyl]amine with tetraethyl orthosilicate.The SPME fiber was prepared by coating hybrid aerogel onto the surface of stainless steel wire,and the analytical method was established after being combined with gas chromatography,then it was used to detect trace PAHs in rainwater and river water.In this reach,tris-[3-(trimethoxysilyl)propyl]amine was both an organosilane coupling agent and a hydrophobic modifier,which not only improved the mechanical strength but also regulated the hydrophobicity of silica aerogel.2.An ionic liquid(1,1'-bis[3-(trimethoxysilyl))propyl]-4,4'-bipyridyl dibromide)modified silane coupling agent was synthesized by the reaction of 4,4'-bipyridine and3-chloropropyltrimethoxysilane.It was co-precursored with tetraethyl orthosilicate in the preparation of silica aerogel.The method of simultaneous hydrolysis introduced the ionic liquid into the network of silica aerogel by covalent bonding.This ionic liquid hybrid silica aerogel had a three-dimensional porous structure and it also combined the excellent extraction properties of ionic liquid and silica aerogel.In addition,the ionic liquid also provided ?-?interaction with aromatic analytes(such as PAHs),so the hybrid silica aerogel exhibited good extraction selectivity for such analytes.It was applied as a new SPME coating for high-selective and high-sensitive analysis of PAHs in environmental samples.