Analytical

As a result of “The Norwegian Geochemical Standard Sample Project”, three reference samples were distributed by NPD to several laboratories worldwide. Results were analysed statistically to obtain most likely values and permissible ranges.

To ensure good and reproducible results over time, these reference samples are run regularly and at least every 10th sample. Results from reference samples are checked against the permissible ranges given in NIGOGA. Below is an example of results obtained from analysis of a saturated fraction by GC. If the results fall outside the permissible range, the instrument is recalibrated and the batch analysed again. In addition, results are plotted in a control chart to monitor long term reproducibility.

Quality control report (NSO-1) of T:\GC-SAT\SAT0001\002B0201.TCA 
Description: NSO-1 #11.4 saturated fraction.

Date: 08-May-2000
Time: 18:23:27

Parameter
Permissible range
Lower
Permissible range
Upper
Most likely value
Measured
Status
Pr/n-C17
n-C30/n-C20
n-C17/(n-C17+n-C27)
CPI1
0.55
0.20
0.75
0.99
0.66
0.32
0.82
1.09
0.60
0.29
0.79
1.02
0.63
0.22
0.81
1.07
OK
OK
OK
OK

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