A cryogenic enrichment technique for gas chromatographic detection of S2F10 in SF6 discharges

In conventional gas chromatography (GC), S₂F₁₀ in the presence of SF₆ is only detectable down to a concentration of ~50 ppm (parts per million). This limit, which is largely due to the interference of the SF₆ peak with S₂ F₁₀, can be reduced by using an enrichment procedure similar to the online procedure used by KEMA, (J.A.J. Pettinga, 1985) whereby S₂F₁₀ is selectively trapped, increasing its concentration relative to SF₆, 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 SF₆ decomposition have also been examined using this system. Contrary to the KEMA results, S₂OF₁₀ was found to have a lower retention time than S₂F₁₀ in both the cryogenic enrichment system and in conventional GC. Analyses of corona-discharged SF₆ are reported, showing that this technique has at least a 1000-fold improvement in sensitivity over conventional GC