Interlaboratory comparison of SF6-determinations used within the framework of tracer releases

An international intercomparison exercise, for determination of trace amounts of SF6 in air was set up, to make interchange of experimental results or common tracer experiments possible between European laboratories. SCK, Belgium made 6 SF6 samples in the 10 ppt to 10 ppb range. Samples were analyzed by CEN (F), CERL (UK), JRC (I), KEMA (NL), LHW (NL), NILU (N), APL (DK), WDB (FRG) and SCK (B). Very good agreement was obtained between SCK, CERL, APL and NILU. LHW and KEMA obtained systematically lower results than those four laboratories; the problem might originate in manufacturing of mother samples under high pressure. CEN and WDB work in a higher concentration range and their analysis of trace amounts is less accurate. JRC samples were contaminated and accuracy of their analysis cannot be evaluated. SF6 samples in PVC plastic bags are not stable enough over long periods, especially with ambient temperature higher than 300C. Transport of samples in plastic bags over long distances is not advisable when transport conditions cannot be well controlled