The National Physical Laboratory (NPL) in the United Kingdom provides traceable gas reference materials for calibration of atmospheric gas analysers where low uncertainty measurements of the amount fraction and/or stable isotope ratio of atmospheric components are required. Primary gas Reference Materials (PRMs) are available for amount fraction traceable to the SI and, for CO 2 amount fractions between 380 and 800 μmol mol -1 , can be linked to the WMO-CO 2 -X2019 scale via the BIPM.QM-P5 comparison. Traceable stable isotope ratio PRMs for the most potent anthropogenic greenhouse gases and climate relevant species including carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O) and carbon monoxide (CO) are available and are traceable to current globally recognised isotope reference scales including VPDB for δ 13 C-CO 2 , δ 18 O-CO 2 and δ 13 C-CH 4 , VSMOW/SLAP for δ 2 H-CH 4 and δ 18 O-N 2 O and Air N 2 for δ 15 N-N 2 O. This paper details recent advances in the production of PRMs at NPL and outlines the PRMs and services currently being developed.
Hill-Pearce et al. (Thu,) studied this question.