Preparation and Application of Siloxane Modified Polyimide Coating for Solid Phase Microextraction

Siloxane modified polyimide was synthesized from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-diaminodiphenylether and 1,3-bis(-3-aminopropyl)-tetramethyldisiloxane, using N,N-dimethylformamide as solvent, and used as coating material for quartz fibre in SPME. Molecular structure, thermostability and surface morphology of the siloxane modified polyimide was studied by IRS, TG and SEM. It was shown that by introduction of siloxane chain segments into molecular structure of polyimide, the flexibility is raised, the polar action between the molecular chains is decreased and the adsorptivity is improved, and that by dehydration at high temperature, the coating material is bonded with the quartz fibre on its surface, making the coating to adhere more firmly and to behave a more stable character. SPME with quartz fibre coated with the siloxane modified polymide was applied to GC-determination of 7 benzene homologues in water samples. Good efficiency of separation was obtained, and in the GC analysis for the 7 benzene homologues, values of RSD′s (n=6) found were in the range of 4.1%-6.0%, detection limits (3S/N) found were in the range of 0.02-0.11 mg·L-1, and values of recovery found by standard addition method were in the range of 98.0%-117%.