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New CH3CCl3 standards were prepared in 2001-2003 from new reagent material (99.8% purity).
The 1996 scale was based on standards made from reagent now known to
contain several impurities (approx 94% pure). The interim 2002 scale was based
on these new standards, but was not well-defined at mixing ratios less than 40 ppt.
The following table defines the 2003 scale. Two equations are used to convert the 1996
scale and the interim 2002 scale to the current 2003 scale.
CH3CCl3 calibration standards
updated: October 2003
year prepared assigned residual
    (ppt) (ppt) (ppt)
ALM-64608B 2001 99.1 99.5 0.4
ALM-65990A 2002 124.8 125.1 0.3
ALM-33800A 2002 104.0 102.7 -1.4
ALM-38422A 2002 187.2 187.1 -0.1
SX-3506 2002 76.7 76.6 -0.1
SX-3518 2003 20.7 20.6 0.0
SX-3519 2003 40.8 40.5 -0.2
SX-3522 2003 33.8 33.9 0.1
std dev 0.58
Convert 2002 scale to 2003 scale
Y = -2.0022e-4*X^2 + 1.0402*X - 2.68
where X = conc (ppt) from 2002 scale
convert 1996 scale to 2003 scale
Y = -1.6120e-4*X^2 + 0.9654*X + 0.2
where X = conc (ppt) from 1996 scale