NIST Gas Standards Containing Volatile Organic Compounds In Support Of Ambient Air Pollution Measurements
Free (open access)
357 - 365
G. C. Rhoderick
Since the late 1970s the National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, USA, has been developing and supplying reference materials (RMs) in support of gas measurements for measuring ambient air pollution. These RMs have been developed for federal and state governments in the United States (US), such as the US Environmental Protection Agency (EPA) and the State of California Air Resources Board (CARB), as well as academia, research laboratories such as the National Center for Atmospheric Research (CARB), and other laboratories around the world. Many of these volatile organic compounds (VOCs) pose health concerns and are monitored at ground level to assist U.S. government agencies in assessing the need for emission studies and controls. Ozone is also a ground level pollutant of great concern. Hydrocarbons are ozone precursors and are measured to track, in particular, automobile emissions. RMs are split into two groups containing either multicomponent mixtures of VOCs or non-methane hydrocarbons (NMHCs). Typically these RMs are produced at the 0.02–10 nmol/mol (ppb) level. The research into the preparation and stability of such chemical compounds contained in gas mixtures has led to the development of two Standard Reference Materials (SRMs); a 30- component VOC (SRM 1804) and 18-component NMHC (SRM 1800) at 5 nmol/mol per component. NIST has participated in international comparisons with other National Metrology Institutes (NMIs) through bilaterals and CCQM key and pilot comparisons for many of these VOCs and NMHCs. Results of these comparisons have shown equivalency among these NMIs, helping to underpin their measurement and standards claims. Development of these SRMs and RMs, as well as the international comparisons will be discussed. Keywords: standard reference material (SRM), reference material (RM), volatile organic compounds (VOCs), non-methane hydrocarbons (NMHC), primary standard mixtures (PSMs), air pollution measurements.
standard reference material (SRM), reference material (RM), volatile organic compounds (VOCs), non-methane hydrocarbons (NMHC), primary standard mixtures (PSMs), air pollution measurements.