title: International comparison of a hydrocarbon gas standard at the picomol per mol level.
abstract: Studies of climate change increasingly recognize the diverse influences of hydrocarbons in the atmosphere, including roles in particulates and ozone formation. Measurements of key nonmethane hydrocarbons (NMHCs) suggest atmospheric mole fractions ranging from low picomoles per mol (ppt) to nanomoles per mol (ppb), depending on location and compound. To accurately establish mole fraction trends and to relate measurement records from many laboratories and researchers, it is essential to have accurate, stable, calibration standards. In February of 2008, the National Institute of Standards and Technology (NIST) developed and reported on picomoles per mol standards containing 18 nonmethane hydrocarbon compounds covering the mole fraction range of 60 picomoles per mol to 230 picomoles per mol. The stability of these gas mixtures was only characterized over a short time period (2 to 3 months). NIST recently prepared a suite of primary standard gas mixtures by gravimetric dilution to ascertain the stability of the 2008 picomoles per mol NMHC standards suite. The data from this recent chromatographic intercomparison of the 2008 to the 2011 suites confirm a much longer stability of almost 5 years for 15 of the 18 hydrocarbons; the double-bonded alkenes of propene, isobutene, and 1-pentene showed instability, in line with previous publications. The agreement between the gravimetric values from preparation and the analytical mole fractions determined from regression illustrate the internal consistency of the suite within ±2 pmol/mol. However, results for several of the compounds reflect stability problems for the three double-bonded hydrocarbons. An international intercomparison on one of the 2008 standards has also been completed. Participants included National Metrology Institutes, United States government laboratories, and academic laboratories. In general, results for this intercomparison agree to within about ±5% with the gravimetric mole fractions of the hydrocarbons.
authors.affiliation: Chemical Sciences Division, Materials Measurement Laboratory, National Institute of Standards and Technology , 100 Bureau Drive, MS-8393, Gaithersburg, Maryland 20899-8393, United States.
authors.forename: George C
authors.initials: GC
authors.lastname: Rhoderick
authors.forename: David L
authors.initials: DL
authors.lastname: Duewer
authors.forename: Eric
authors.initials: E
authors.lastname: Apel
authors.forename: Annarita
authors.initials: A
authors.lastname: Baldan
authors.forename: Bradley
authors.initials: B
authors.lastname: Hall
authors.forename: Alice
authors.initials: A
authors.lastname: Harling
authors.forename: Detlev
authors.initials: D
authors.lastname: Helmig
authors.forename: Gwi Suk
authors.initials: GS
authors.lastname: Heo
authors.forename: Jacques
authors.initials: J
authors.lastname: Hueber
authors.forename: Mi Eon
authors.initials: ME
authors.lastname: Kim
authors.forename: Yong Doo
authors.initials: YD
authors.lastname: Kim
authors.forename: Ben
authors.initials: B
authors.lastname: Miller
authors.forename: Steve
authors.initials: S
authors.lastname: Montzka
authors.forename: Daniel
authors.initials: D
authors.lastname: Riemer