Preparation And Application Of Polyimide/Silica Hybrid Coating For Solid Phase Microextraction

Solid-phase microextraction technology is a new extraction techniques and it has theadvantages of convenient operation,rapid separation and analysis,high sensitivity,and lesssample consumption.The technology has been widely applied in environmental pollution,foodtesting,medical and other fields.The key to the success of solid-phase microextraction is thenature of the coating.The coatings should be able to meet the strong extraction capability forthe analyte and a relatively short period of time to reach equilibrium.The analyte can quicklydesorption from the extraction head.The coating follows the principle of "like dissolveslike".An extract head can not be able to extract all the compounds.In order to enhance theapplicability of solid-phase microextraction technology,researchers have been dedicated to theexploration of new coating materials,coating preparation techniques and the extraction device.The solid-phase microextraction coating of PI/SiO₂was prepared by the sol-geltechnology.The polyamic acid was synthesized from pyromellitic acid dianhydride （PMDA）and4,4’-diaminodiphenylether（ODA）.Tetraethoxysilane was hydrolyzed to generate thesilicon alcohol.After dehydration cyclization at high temperature,the PI/SiO₂were formed bythe reaction of condensation between the polyamic acid and the silicon alcohol.PI/SiO₂werebonded on the quartz fiber surface with coupling agent.The surface morphology of the coatingwas investigated by scanning electron microscope.The structure of the coating was studied byIR.The thermostability of the coating was examined by thermal anlysis.Monochlorobenzene,o-dichlorobenzene and m-dichlorobenzene in aqueous phase were detected by head space-solidphase microextraction-gas chromatography.The correlation coefficients of monochlorobenzen-e,o-dichlorobenzene and m-dichlorobenzene（r） were0.9991,0.9992and0.9975.The detectionlimits of monochlorobenzene,o-dichlorobenzene and m-dichlorobenzene were0.08mg/L,0.03mg/Land0.05mg/L.The relative standard deviations were6.34%,4.39%and4.76%（n=5）repectively.The result showed that the sol-gel coating could be used at high temperature anddurable,high efficience,inexpensive.So it will be widely used in the future.