Bilateral comparison of analytical capabilities for nitrogen dioxide (NO2) gas mixtures

Project Description

In the last CMCs review (cycle XXV) LNE had to review its CMCs for NO2 in the range between 10 and 1000 nmol/mol. As there is no comparison available to support the evidence, we proposed to organise a bilateral comparison between LNE/METAS; this proposal was accepted during the last SC Gas Analysis meeting.

This bilateral comparison will consist in analysing a NO2 gas mixture in a cylinder at 200 nmol/mol in air from Air Liquide: this gas mixture will be analysed by LNE, then by METAS and again by LNE, and finally we will determine the degree of equivalence.

Progress Report 2025-03-05

The bilateral comparison led in 2024 consisted in analysing a NO2 gas mixture in air in a cylinder at 200 nmol/mol from Air Liquide: this gas mixture was analysed by LNE, then by METAS and again by LNE from February to July 2024.

After processing the results and calculating the degree of equivalence, the amount fractions determined by LNE and METAS were significantly different. No explanations were identified.

In December 2024, it was decided to continue this comparison by circulating a NO2 generator (REGAS) from METAS. METAS will calibrate the REGAS generator at two amount fractions (150 and 300 nmol/mol), then LNE will determine the amount fractions and at the end of the comparison, METAS will calibrate again the REGAS generator.
This comparison will be led in 2025.The DRAFT A is in progress.

The progress of this comparison was presented at the SCGA meeting in February 2025 and a comparison proposed for 2025 was accepted.

Progress Report 2024-04-22

LNE selected a NO2 gas mixture in a cylinder at about 200 nmol/mol in air from Air Liquide in February 2024 and calibrated it. This gas mixture was sent to METAS by LNE in March.

In April, METAS will calibrate the gas mixture.