Highly Accurate Nitrogen Dioxide (NO₂) in Nitrogen Standards Based on Permeation

Abstract

The development and operation of a highly accurate primary gas facility for the dynamic production of mixtures of nitrogen dioxide (NO(2)) in nitrogen (N(2)) based on continuous weighing of a permeation tube and accurate impurity quantification and correction of the gas mixtures using Fourier transform infrared spectroscopy (FT-IR) is described. NO(2) gas mixtures in the range of 5 μmol mol(-1) to 15 μmol mol(-1) with a standard relative uncertainty of 0.4% can be produced with this facility. To achieve an uncertainty at this level, significant efforts were made to reduce, identify and quantify potential impurities present in the gas mixtures, such as nitric acid (HNO(3)). A complete uncertainty budget, based on the analysis of the performance of the facility, including the use of a FT-IR spectrometer and a nondispersive UV analyzer as analytical techniques, is presented in this work. The mixtures produced by this facility were validated and then selected to provide reference values for an international comparison of the Consultative Committee for Amount of Substance (CCQM), number CCQM-K74, (1) which was designed to evaluate the consistency of primary NO(2) gas standards from 17 National Metrology Institutes.

Reply to the comments of Reviewer 2

“…Additionally, a second calibration mass (CM2) of same volume but different mass is measured every six calibration points to correct for any potential buoyancy change affecting the measurement of CM1. The masses of CM1 and CM2 are traceable to the Swiss realisation of the kilogram (Fuchs et al, 2012;Marti et al, 2015;Marti, 2017, and references therein). All weight measurements and associated corrections realised with MSB-Violetta are fully automated.…”

Dynamic–gravimetric preparation of metrologically traceable primary calibration standards for halogenated greenhouse gases

“…O'Keeffe and Ortman, 1966;Scaringelli et al, 1970;Brewer et al, 2011;Flores et al, 2012;Haerri et al, 2017). It is routinely used at METAS following a procedure in compliance with international standards (ISO 6145-10, 2002;ISO 6145-7, 2009).…”

Dynamic-gravimetric preparation of metrologically traceable primary calibration standards for halogenated greenhouse gases

“…Reference gas generation by applying the permeation method combined with dynamic dilution is an established, standardised technique, particularly for reactive gases (e.g., O'Keeffe and Ortman, 1966;Scaringelli et al, 1970;Brewer et al, 2011;Flores et al, 2012;Haerri et al, 2017). It is routinely used at METAS following a procedure in compliance with international standards (ISO 6145-10, 2002;ISO 6145-7, 2009).…”