QUANTITATIVE MEASUREMENT OF ANALYTE GASES IN A MICROWAVE SPECTROMETERUSING A DYNAMIC SAMPLING METHOD

This article reports quantitative measurement of concentrations of wat er vapor (absorption line at 22.235 GHz) and ethylene oxide (absorptio n line at 23.123 GHz) in different gas mixtures by means of a microwav e spectrometer. The problem of absorption line broadening and the gas memory problem inherent in the quantitative analysis of gases using mi crowave molecular rotational spectroscopy have been solved. The line b roadening problem was minimized by gas dilution with nitrogen and the gas memory problem was effectively reduced by means of a dynamic sampl ing method. Calibration of ethylene oxide with a dilution factor of 5 has demonstrated that the standard deviations of the calibration data were less than 4.2%. A typical ethylene oxide sterilization production cycle was chosen to monitor chamber ethylene oxide concentrations in the gas dwell phase and the repeatability of these real time measureme nts was 2.7%. (C) 1996 American Institute of Physics.