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).