IsoPrime User’s Guide
Version 1.01 Background Information Page 151 of 219
OTHER ANALYTICAL CONSIDERATIONS
The following sections describe the data reduction algorithms used in the software.
GENERAL SEQUENCE OF DATA REDUCTION
The following calculations are performed where necessary for any gas:
Convert the reference gas delta values to the standard format for further calculation.
For example, if CO
2
is being analysed and the reference deltas are input as (13) and
(18), it is necessary to convert these values to (45) and (46) for further use. This may
be carried out automatically using the Craig correction.
Convert the sample delta value, measured with respect to the laboratory standard, to a
delta value with respect to the international standard.
This conversion is carried out using the following formula:
(sample w.r.t. International) = (sample) + (reference w.r.t. international) +
(sample) * (reference w.r.t. international) / 1000
Convert the observed delta values of a gas comprising more than one element to the
delta values for the pure element.
The most familiar example is probably the Craig correction for CO
2
(see above).
The other common case is for sulphur analysis using the 64 and 66 peaks of SO
2
.
To carry out these calculations, generally a matrix is set up using constants from the parameter
file (only accessible at supervisor level), such that:
1(corrected) = C1 * 1- C2 * 2(corrected)
and:
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