A cryogenic enrichment technique for gas chromatographic detection of S/sub 2/F/sub 10/ in SF/sub 6/ discharges

In conventional gas chromatography (GC), S/sub 2/F/sub 10/ in the presence of SF/sub 6/ is only detectable down to a concentration of approximately 50 ppm (parts per million). This limit, which is largely due to the interference of the SF/sub 6/ peak with S/sub 2/F/sub 10/, can be reduced by using an enrichment procedure similar to the online procedure used by KEMA, (J.A.J. Pettinga, 1985) whereby S/sub 2/F/sub 10/ is selectively trapped, increasing its concentration relative to SF/sub 6/, followed by subsequent GC analysis. Using commercially available components, the authors have set up a similar system and have evaluated some of the parameters influencing peak resolution and detectability, such as trapping temperature, desorption rates, and carrier gas flow. Other compounds relevant to SF/sub 6/ decomposition have also been examined using this system. Contrary to the KEMA results, S/sub 2/OF/sub 10/ was found to have a lower retention time than S/sub 2/F/sub 10/ in both the cryogenic enrichment system and in conventional GC. Analyses of corona-discharged SF/sub 6/ are reported, showing that this technique has at least a 1000-fold improvement in sensitivity over conventional GC.<
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