Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Development of a Northern Continental Air Standard Reference Material



George C. Rhoderick, Duane Kitzis, Michael E. Kelley, Walter R. Miller Jr., Bradley Hall, Edward Dlugokencky, Pieter Tans, Antonio M. Possolo, Jennifer Carney


The National Institute of Standards and Technology (NIST) recently began to develop standard mixtures of greenhouse gases as part of a broad program mandated by the 2009 United States Congress to support research in climate change. To this end, NIST made suites of gravimetrically assigned primary standard mixtures (PSMs) comprising carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in a dry-natural air balance at ambient molar fraction levels. In parallel, the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado, charged thirty aluminum gas cylinders with northern hemisphere air at Niwot Ridge, Colorado. NOAA, the Central Calibration Laboratory (CCL) for the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) Program for CO2, CH4 and N2O, analyzed the gas cylinder samples for these components compared to their manometric (CO2) and gravimetric (CH4 and N2O) calibration standards. Subsequently, NIST analyzed the same cylinder samples with instrumentation calibrated in terms of the NIST PSM mixture suites, resulting in an independent set of certified concentration values. These mixtures, which constitute NIST Standard Reference Material (SRM) 1720 Northern Continental Air, were certified for ambient molar fractions of CO2, CH4 and N2O, represent the first of their kind for NIST. Relative expanded uncertainties at the 95 % confidence interval are
Journal of Analytical Chemistry


Standard Reference Material (SRM), Long-Lived Greenhouse Gases (LLGHG), Northern Continental Air, Gravimetric Preparation, Primary Standard Mixture (PSM)
Created February 18, 2016, Updated November 10, 2018