24 
BSH Report No. 56 
IRMS data 
Laboratory Performance RSD 
(Based on 6 13 C values of n-Alkanes) 
C22 
In compound specific 8 13 C- isotope ratio mass spectrometry, one criterion 
commonly used is 1 %o (per mil PDB). This is partly given by the instrumental 
measuring uncertainty of around 0.5%o. This means, if one sample’s measuring 
is within the range of 1 per mil of another sample, the 8 13 C- content of the mate 
rial can be considered the same, or cannot be further distinguished. 
Apart from the laboratory performance where the RSD is used to describe the 
repeatability (Fig. 13), the defining feature here is the absolute difference of 
S 13 C with a threshold of 1 %o. 
The NFI followed a straightforward approach and performed analysis, in dupli 
cates, on the solutions as received without fractionation or similar preparative 
techniques. 
[613C] Means of sample #1 {n=1), #10 {n=2)