Update: September, 2014
The WMO/GAW X2006 SF6 scale was updated to X2014 on 18 September 2014. The X2014 scale supercedes the X2006 scale.
The X2014 SF6 scale is defined by 17 primary standards over the range 2-20 pmol mol-1 (ppt), prepared by static gravimetric dilution in 5.9-L aluminum cylinders. Assigned values were determined by fitting a 2nd order polynomial to the response of each standard (relative to a 8.25 ppt natural air secondary standard) measured using an HP6890 GC with electron capture detection (GC-ECD). Analysis repeatability (precision) was typically less than 0.3% (one standard deviation).
Conversion from X2006 to X2014:For SF6 > 2 ppt: The conversion has an uncertainty of ± 0.01 ppt
Please use caution applying this equation to SF6 > 10 ppt. Results will only be approximate.
Table 1: Comparison of X2006 to X2014 SF6 scales over the range 1-12 pmol mol-1 (ppt).
*Values above 10 ppt are included for illustration purposes, but are beyond the range of the X2006 scale.
Table 2: Primary Standards that define the X2014 SF6 scale. Uncertainties associated with prepared mole fractions are approximately one standard deviation. Mole fractions assignments are based on GC-ECD analysis, using a 2nd order polynomial response function.
|Cylinder #|| Prepared