Polyetherimide-silicone:: a 10 μm ultrathin composite membrane for faster and more sensitive membrane introduction mass spectrometry analysis

A polyetherimide (polyester)/silicone (PEI/S) sheet composite membrane with a 10 mu m thick cross-linked silicone layer is found to display the required mechanical properties to work efficiently as the solution/high vacuum interface in membrane introduction mass spectrometry (MIMS) analysis of volatile organic compounds (VOC) in water. Owing to much shorter response and recovery times, the PEI/S membrane allows much faster analysis and calibration procedures as compared to the 250 mu m silicone membrane usually used in MIMS, When using EI, owing to excessive water permeation, responses (signal intensity) for the PEI/S membrane are not always superior, being analyte-dependent, For the more polar VOCs, however, the PEI/S membrane shows 2-3 times greater responses, improving their relatively poor MIMS detection limits, When water-methane chemical ionization is applied, the problem of excessive water permeation is attenuated, and the PEI/S membrane displays greatly superior responses.