Separation of DMMP/Water Vapor with PDMS/Silica Membranes for the Sample Inlet of Ion Mobility Spectrometers

In order to obtain an ideal sample inlet membrane for ion mobility spectrometers (IMS), fumed silica was modified using hexamethyldisilazane and was incorporated into the matrix of polydimethylsiloxane (PDMS) silicone rubber to fabricate PDMS/silica mixed matrix membranes with different thickness. Dimethyl methylphosphonate (DMMP) permeability of thin silicone rubber membranes (SRM) with the least thickness of approximate 5 mu m was studied. DMMP concentration interior to the SRM showed the linear correlation to that external to the SRM. Thickness and temperature of SRM were two important factors influencing the permeation proportion of DMMP. Most water vapor was prevented to transfer through the SRM. In addition, the SRM had a good selectivity of DMMP/water vapor and the maximum separation factor was 4.82 when the temperature of membranes reached 80 degrees C.