Determination of Trace Impurities in Sulfur Hexafluoride Gas by Thermal Conductivity and Flame Photometry in Series

摘要

Relative errors for SO sub 2 F sub 2 determination are less than 10% and that repetition is very good. For the determination of SOF sub 2 , the relative error is comparatively higher but usually less than 30%. This is because the content of SOF sub 2 is very low, and the correction factor is only 0.08. These experiments prove that by using a method consisting of thermal conductivity and flame photometry in series to measure sulphur fluoride, reliable test results can be obtained. When 2 ml samples are injected, the lowest detectable concentrations are: SO sub 2 F sub 2 5 ppM; SOF sub 2 0.5 ppM, much better than present documented values. Because the sulphur in SF sub 6 and sulphur fluoride is comparatively stable, it is difficult to reduce it in the hydrogen-rich flame of the flame photometric detector (FPD). The sensitivity of the FPD is therefore lower than that for measuring most sulphur-containing organic material, moreover the slopes of the calibration graphs are also lower (only about 1.5) than the theoretical value (=2); because of this, before measuring, the FPD must be adjusted to its most sensitive working condition. (ERA citation 10:042554)