Preparation of a novel coating is one of the keys to solid phase microextraction.A new method was proposed to prepare a chitosan microprobe with a film thickness of several dozen micrometers with the phase inverse technique by using a microporous polyacrylonitrile (PAN) hollow fiber with a diameter of 1.5 mm as template.The dilute acetic acid solution of chitosan and glutaraldehyde was added into the hollow fiber

a quartz fiber was inserted into the hollow fiber as supporter and then the hollow fiber was placed in the NaOH solution

because of the porosity of hollow fiber

NaOH diffused and contacted with acetic acid

then the chitosan thin film was formed.For intensifying the adsorption of acidic compounds

the probe was then modified with polyethyleneiminate (PEI).The SEM photos showed that the probe obtained with this process was 17 μm thick.The PEI-modified chitosan probes showed stronger adsorption of furomeside.Using NaOH as desorber

a concentration factor over 10 was observed and the solute concentration in the desorber was linear with that in the original samples.The operation is convenient and easy to realize automation.