IRMS data
25
C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33
Fig. 15: d13C-means of
sample 1, 10 from IAEA with
standard deviation as error
margin. IAEA measured in
triplicates (n=3).
IAEA performed analysis In triplicates and used a more elaborated methodology
compared to the NFI, with following steps Involved:
• Preparation of a linear chained hydrocarbon fraction of the paraffin wax mixture
• Reference C0 2 , calibrated against PDB, was Introduced five times at the
beginning, three times at the end of every Isotopic GC determination.
• Calibration standards of n-alkanes were Introduced every 4 samples.
For the duplicate analysis, the results of both laboratories show that the 8 13 Ccontent
of each Individual n-alkane Is within the range of 1 %o (Fig. 15 and
Fig. 14). In case of IAEA’s duplicate analysis (Fig. 15), sample 10 shows unstable
13 C-contents along the series of n-alkanes. Especially the sudden Increase
(< 1 per mil) from C28 to C29 does not correspond to the average composition
of the neighbouring n-alkanes.
However, there was an outlier In the NFI’s
duplicate run of the first sample, resulting In
Increased RSD (repeatability) and very low
matching-ratios (< 10% for comparison of
set 1 “1 on 2” and “1 on 3” and >59% for “1
on 10”). This was very obvious even without
the application of any statistical test (e. g.
Grubbs, etc.). After eliminating the outlier by
Ignoring the whole run and using just the
data from the second analysis (Instead of the
mean, only values from the second run were
considered, n=1), the comparison turned out
to be very well In accordance (> 83% for
comparison of set 1 “1 on 2” and “1 on 3”
and 100% for “1 on 10”).
IAEA
NFI
<1
<1
Set_l 1 on 2
100%
83%
1 on 3
100%
100%
2 on 3
100%
100%
Set_2 4 on 5
8%
31%
4 on 6
0%
8%
5 on 6
0%
0%
Set_3
Dup
7 on 8
7 on 9
8 on 9
Ion 10
92%
77%
85%
92%
92%
92%
83%
100%
Tab. 5: IRMS-Conclusion matrix
