CAPTIONS
Table 1. Results obtained by 2×EA/IRMS and 3×EA/IRMS
measurements of international reference materials and laboratory
standards.a
a n.a. = not applicable; n.d. = not determined
b Values and uncertainties are as indicated in the
references. Values for the laboratory standards UNIL Urea 1–3 were
obtained via conventional replicate (n ) EA/IRMS measurements
(September–October 2022) and calibration with international RMs.
c Uncertainties for the laboratory standards
correspond to one standard deviation (1-sigma) of n measurements.
Figure 1. Typical 3×EA/IRMS chromatogram for carbon (A) and
nitrogen (B) isotope analysis. The traces of m /z 44, 45,
and 46 and of m /z 28, 29, and 30 represent ions of the
CO2 and N2 reference gases (three
rectangular peaks) followed by peaks from three consecutive combusiton
reactions of tin capsules containing aliquots of the same or different
sample or standard. The traces of the m /z ratios 45/44 and
46/44 show the contribution of N2 to the background (A).