INVESTIGATION OF MASS-SPECTROMETRIC SYSTEMS USING SILICONE MEMBRANES AND CAPILLARY FOR DIRECT INLET OF GAS SAMPLES

The paper presents the results of a study of the gas permeability of thin silicone membranes used as part of a direct sample inlet system into an MS7-200 quadrupole mass spectrometer. Materials of 4 sorts were studied: Sylgard-184, PlatSet-30, Lasil-T4 and Lasil-C. The thickness of the fabricated membranes varied from 45 to 75 μm. PlatSet-30, 50 µm was determined to be the most permeable membrane. The mass spectra obtained using a membrane sample inlet system and a direct capillary sample inlet system were also compared. The following gases were used as the test ones: atmospheric air, sulfur dioxide in nitrogen, and pentane in air. The advantages of membrane inlet compared to capillary are shown, namely, an increase in sensitivity for individual components at low sample concentrations. The main disadvantage of silicone membranes is their rather high probability of damage when installed in a membrane inlet system.