NIST Gravimetrically Prepared Atmospheric Level Methane in Dry Air Standards Suite

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• 作者：George C. Rhoderick ; Jennifer Carney ; Franklin R. Guenther
• 刊名：Analytical Chemistry
• 出版年：2012
• 出版时间：April 17, 2012
• 年：2012
• 卷：84
• 期：8
• 页码：3802-3810
• 全文大小：283K
• 年卷期：v.84,no.8(April 17, 2012)
• ISSN：1520-6882

文摘

The Gas Metrology Group at the National Institute of Standards and Technology was tasked, by a congressional climate change act, to support the atmospheric measurement community through standards development of key greenhouse gases. This paper discusses the development of a methane (CH₄) primary standard gas mixture (PSM) suite to support CH₄ measurement needs over a large amount-of-substance fraction range 0.3鈥?0鈥?00 渭mol mol^鈥?, but with emphasis at the atmospheric level 300鈥?000 nmol mol^鈥?. Thirty-six CH₄ in dry air PSMs were prepared in 5.9 L high-pressure aluminum cylinders with use of a time-tested gravimetric technique. Ultimately 14 of these 36 PSMs define a CH₄ standard suite covering the nominal ambient atmospheric range of 300鈥?000 nmol mol^鈥?. Starting materials of pure CH₄ and cylinders of dry air were exhaustively analyzed to determine the purity and air composition. Gas chromatography with flame-ionization detection (GC-FID) was used to determine a CH₄ response for each of the 14 PSMs where the reproducibility of average measurement ratios as a standard error was typically (0.04鈥?.26) %. An ISO 6134-compliant generalized least-squares regression (GenLine) program was used to analyze the consistency of the CH₄ suite. All 14 PSMs passed the u-test with residuals between the gravimetric and the GenLine solution values being between 鈭?.74 and 1.31 nmol mol^鈥?; (0.00鈥?.16)% relative absolute. One of the 14 PSMs, FF4288 at 1836.16 卤 0.75 nmol mol^鈥? (k = 1) amount-of-substance fraction, was sent to the Korea Research Institute of Standards and Science (KRISS), the Republic of Korea鈥檚 National Metrology Institute, for comparison. The same PSM was subsequently sent to the National Oceanic and Atmospheric Administration (NOAA) for analysis to their standards. Results show agreement between KRISS-NIST of +0.13% relative (+2.3 nmol mol^鈥?) and NOAA-NIST of 鈭?.14% relative (鈭?.54 nmol mol^鈥?).