As part of the quantiAGREMI project a comparison of dry and wet NH3 reference gas mixtures (RGMs) at nmol∙mol-1 (ppb) levels was performed with four traceability chains: (1) dynamic dilution of gravimetric gas mixtures, (2) dynamic reference gas mixtures generated by the permeation method, (3) a laser based spectral method, and (4) dynamic reference gas mixtures generated using the evaporation method.
The obtained results showed that, overall, the generators are operating correctly with a good reproducibility (better than 0.8% in dry and wet air) and a good linearity on the measurement range from 0 to 400 nmol∙mol-1 in dry and wet air. The expanded uncertainties (0.023 to 0.031) on the slope of the regression line between the amount fractions of the generated gas mixtures and spectroscopic measurement results are consistent for all gas generators. However, while the generators agreed pairwise, overall agreement was absent. The sources of this discrepancy are now tracked down by the participating NMIs.
Average slopes of PTB spectroscopic measurement results and associated uncertainties determined for the NH3 generators of METAS, VSL and LNE in dry air.
Average slopes of PTB spectroscopic measurement results and associated uncertainties determined for the NH3 generators of METAS, VSL and LNE in wet air.