Preparation And Application Of Organic Silicon Polyimides Solid Phase Microextraction Head

Pretreatment before sample analysis is necessary,it can make components purified,separated and enriched.However tradition sample pretreatment has the disadvantages of largequantities of solvents,low selectivity and big errors.Solid-phase microextraction technologyhas the advantages of short operation time,small sample amount,good reproducibility andhigh selectivity.Its basic principle is that to make adsorption-extraction coating immobilizedon the surface of matrix by the physical or chemical method,then targets are concentrated bycoatings direct or indirect contact with samples.Targets are analysised after thermaldesorption.Extraction quantity,selectivity and sensitivity are determined by the properties ofcoatings.The polyamic acid(PAA) with silicon was synthesized from3,3′,4,4′-benzophenonetetracarboxylic dianhydride(BTDA),4,4′-diaminodiphenylether(ODA)and13-bis(3-aminopropyl)tetramethydisiloxane in the N,N-dimethylformamide.The quartzfiber surface was coated with the polyamic acid.The silicone modified polyimide solid phasemicroextraction head was formed after high-temperature dehydration cyclization undergradient heating.The structure of the coating was studied by IR.The thermostability of thecoating was examined by thermogravimetry.The surface morphology of the coating wasobservated by scanning electron microscope.The benzene,toluene,ethylbenzene,p-xylene,m-xylene,o-xylene and styrene in aqueous phase were detected by head space-solid phasemicroextraction-gas chromatography.The optimum extraction temperature and time weredetermined.The precision of the method and the lowest detection limit were investigated.Therelationship between the peak height and concentration of benzene,toluene,ethylbenzene,p-xylene,m-xylene,o-xylene,styrene were linear.The correlation coefficients(r) were0.9988,0.9819,0.9981,0.9989,0.9971,0.9987and0.9972.The lowest detection limits were0.02mg/L,0.05mg/L,0.09mg/L,0.10mg/L,0.09mg/L,0.11mg/L and0.11mg/L.The relative standarddeviations were5.12%,5.98%,4.52%,4.34%,5.36%,6.01%and4.06%(n=6).The result showsthat polyimide solid phase microextraction coating has a higher adsorption for benzenes,and italso has the advantages of favorable thermal stability,not easily shed,long life.