Hydrocarbon Gas Standards at the pmol/mol Level to Support Ambient Atmospheric Measurements

Published

January 6, 2010

Author(s)

George C. Rhoderick, David L. Duewer, Li Ning, Kathryn DeSirant

Abstract

Studies of climate change increasingly recognize the diverse influences exerted by hydrocarbons in the atmosphere, including roles in particulates and ozone formation. Measurements of key non-methane hydrocarbons (NMHCs) suggest atmospheric concentrations ranging from low pmol/mol (ppt) to nmol/mol (ppb), depending on location and compound. To accurately establish concentration trends and to relate measurement records from many laboratories and researchers, it is essential to have good calibration standards. Several of the world’s National Metrology Institutes (NMIs) are developing primary and secondary reference gas standards at the nmol/mol level. While the U.S. NMI, the National Institute of Standards and Technology (NIST), has developed pmol/mol standards for halocarbons and some volatile organics, the feasibility of preparing well-characterized, stable standards for NMHCs at the pmol/mol level is not yet established. NIST recently developed a suite of primary standards by gravimetric dilution that contains 18 NMHCs covering the concentration range of 60 pmol/mol to 230 pmol/mol. Taking into account the contribution of NMHCs in the high-purity diluent nitrogen used in their preparation, the relative concentrations and short-term stability of these NMHCs in the primary standards have been confirmed chromatographically. However, anomalous results for several of the compounds reflect the difficulties inherent in avoiding contamination and making accurate measurements at these very low levels.

Citation

Environmental Science & Technology

Pub Type

Journals

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Keywords

certified reference material (CRM), errors-in-variables regression (EiV), functional relationship estimation by maximum likelihood (FREML), gravimetric preparation, non-methane hydrocarbon (NMHC), primary standard mixture (RSM)

Citation

Rhoderick, G. , Duewer, D. , Ning, L. and DeSirant, K. (2010), Hydrocarbon Gas Standards at the pmol/mol Level to Support Ambient Atmospheric Measurements, Environmental Science & Technology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=902374 (Accessed October 9, 2024)