H2O-containing permeation tubes are a key component of permeation tube humidity generators (PTGs). These devices are widely used for calibrating atmospheric pressure ionization mass spectrometers (APIMS) and for calibrating other trace humidity analyzers. Here we describe a new calibration service enabling the measurement of PTG permeation rates directly in terms of NIST primary standards of trace humidity generation. Rather than using commonly employed gravimetric methods for permeation tube calibration, the method applied here links the permeation rate of the permeation tube to the thermodynamic properties of ice. We describe the calibration system and demonstrate its performance. Based on a month-long series of calibrations of a single permeation tube maintained at 50 C and with a nominal permeation rate of 37 ng min-1, the measured permeation rate was reproducible to within 0.6 % (standard relative uncertainty).
Citation: Proceedings of Semicon West 2003 Technology Symposium
Pub Type: Journals
calibration, humidity, permeation tube