Highly accurate nitrogen dioxide (NO2) in nitrogen standards based on permeation.

Area of Science:

• Metrology
• Analytical Chemistry
• Gas Metrology

Background:

• Accurate calibration gas mixtures are essential for environmental monitoring and industrial processes.
• Primary gas facilities are critical for establishing traceable reference standards.
• Nitrogen dioxide (NO(2)) standards are vital for air quality assessments.

Purpose of the Study:

• To develop and operate a highly accurate primary gas facility for dynamic NO(2) mixture production.
• To achieve a standard relative uncertainty of 0.4% for NO(2) gas mixtures.
• To validate the facility's performance for international metrology comparisons.

Main Methods:

• Dynamic gas mixture production using a permeation tube with continuous weighing.
• Impurity quantification and correction using Fourier transform infrared spectroscopy (FT-IR).
• Analysis of potential impurities, including nitric acid (HNO(3)).
• Comprehensive uncertainty budget analysis.

Main Results:

• Successful development and operation of a primary gas facility for NO(2) in nitrogen (N(2)).
• Production of NO(2) gas mixtures in the range of 5–15 μmol mol(-1) with 0.4% standard relative uncertainty.
• Identification and quantification of impurities to ensure mixture accuracy.
• Validation of produced mixtures for international comparison (CCQM-K74).

Conclusions:

• The developed primary gas facility provides highly accurate NO(2) gas mixtures.
• The facility's performance meets the stringent requirements for primary gas standards.
• The results contribute to the consistency of NO(2) measurements among National Metrology Institutes.