Atmospheric pressure ionization mass spectroscopy for the study of permeation in polymeric tubing

An atmospheric pressure ionization mass spectrometer (APIMS) is used to determine the permeation coefficients for two widely used kinds of polymeric tubing, PF and Kel-F (PCTFE), at 25 degrees C and 75 degrees C. In the experiments, an ultra-high-purity N/sub 2/ gas flow was maintained through the test tubing. The net impurity uptake by nitrogen due to the permeation of O/sub 2/, CO/sub 2/, H/sub 2/O, and CH/sub 4/ from surrounding air into the polymeric tubing was measured by APIMS with sub-ppb sensitivities. CH/sub 4/ had the highest and O/sub 2/ had the lowest permeation coefficients. Results show that Kel-F was a superior barrier material for all impurities studied. The permeation coefficients for these polymers increased with temperature but did not change significantly with the permeant partial pressure. The permeability of PFA showed a stronger temperature dependence than that of Kel-F.<
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