Study On Amino Silane Coupling Agent Modified Polyimide Solid Phase Micro-extraction Coating

The modified polyimide as solid phase micro extraction coating was studied in this paper.It was compared among double amino silane coupling agent modified polyimide coating solid phase micro extraction,single amino silane coupling agent modified polyimide solid phase micro extraction coating,unmodified polyimide coating solid phase micro extraction and commercialization of coatings. The polyamic acid was synthesized from pyromellitic acid dianhydride(PMDA),3,3′,4,4′-benzophenonetetracarboxylic dianhydride(BTDA) and 4,4′-diaminodiphe- nylether(ODA) in the N,N-dimethylformamide with the 3-Aminopropyltriethoxysilane or 13-bis(3-aminopropyl)tetramethyldisiloxane as the modified silicon source.The quartz fiber was coated by the polyamic acid.The silicon modified polyimide solide phase microextraction coating was formed after high-temperature dehydration cyclization under gradient heating. The surface morphology of the coating was investigated by scanning electron microscope.The structure of the coatings were characterized by IR.The thermal analysis of the coating were carried out by differential scanning calorimetry(DSC) and thermogravimetric analysis(TGA). The solid phase micro-extraction device was made of solid phase microextraction head and the 5 μL gas chromatography microinjector. The benzene,chlorobenzene and nitrobenzene were detected by head space-solid phase microextraction-gas chromatography to determine the optimum extraction temperature and time,to investigate the precision of the method, the lowest detection limit.The relationship between the peaks and concentration of benzene, chlorobenzene and nitrobenzene were linear.The correlation coefficient(R2) of double-modified amino silane coupling agent coating was 0.9947,0.9910,0.9967,respectively. The correlation coefficient of single amino silane coupling agent modified coating was 0.9947,0.9910,0.9967,respectively. The correlation coefficient of unmodified coating was 0.9945,0.9911, 0.9941,respectively. The correlation coefficient of commercialization coating was 0.9954, 0.9958, 0.9976 respectively. The lowest limit of detection of double-modified amino silane coupling agent coating was 0.017 mg/L,0.021 mg/L,0.030 mg/L,respectively. The lowest limit of detection of single amino silane coupling agent modified coating was 0.027 mg/L,0.030 mg/L,0.035 mg/L,respectively. The lowest limit of detection of unmodified coating was 0.037 mg/L,0.044 mg/L,0.051 mg/L,respectively. The lowest limit of detection of commercialization coating was 0.051 mg/L,0.060 mg/L,0.065 mg/L respectively. The relative standard deviation RSD(n=6)were smaller. The relative standard deviation of double-modified amino silane coupling agent coating was 4.62%,3.58%,2.92%,respectively. The relative standard deviation of single amino silane coupling agent modified coating was 5.76%,4.66%,3.39%,respectively. The relative standard deviation of unmodified coating was 6.77%,5.56%,4.49%,respectively. The relative standard deviation of commercialization coating was 6.01%,5.89%,3.96%,respectively.