title: Development of traceable precision dynamic dilution method to generate dimethyl sulphide gas mixtures at sub-nanomole per mole levels for ambient measurement.
abstract: Dimethyl sulphide (DMS) is an important compound in global atmospheric chemistry and climate change. Traceable international standards are essential for measuring accurately the long-term global trend in ambient DMS. However, developing accurate gas standards for sub-nanomole per mole (nmol/mol) mole fractions of DMS in a cylinder is challenging, because DMS is reactive and unstable. In this study, a dynamic dilution method that is traceable and precise was developed to generate sub-nmol/mol DMS gas mixtures with a dynamic dilution system based on sonic nozzles and a long-term (>5 years) stable 10 μmol/mol parent DMS primary standard gas mixtures (PSMs). The dynamic dilution system was calibrated with traceable methane PSMs, and its estimated dilution factors were used to calculate the mole fractions of the dynamically generated DMS gas mixtures. A dynamically generated DMS gas mixture and a 6 nmol/mol DMS PSM were analysed against each other by gas chromatography with flame-ionisation detection (GC/FID) to evaluate the dilution system. The mole fractions of the dynamically generated DMS gas mixture determined against a DMS PSM and calculated with the dilution factor agreed within 1% at 6 nmol/mol. In addition, the dynamically generated DMS gas mixtures at various mole fractions between 0.4 and 11.7 nmol/mol were analysed by GC/FID and evaluated for their linearity. The analytically determined mole fractions showed good linearity with the mole fractions calculated with the dilution factors. Results showed that the dynamic dilution method generates DMS gas mixtures ranging between 0.4 nmol/mol and 12 nmol/mol with relative expanded uncertainties of less than 2%. Therefore, the newly developed dynamic dilution method is a promising reference method for generating sub-nmol/mol DMS gas standards for accurate ambient measurements.
authors.affiliation: Center for Gas Analysis, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea; Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
authors.forename: Mi Eon
authors.initials: ME
authors.lastname: Kim
authors.affiliation: Center for Gas Analysis, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea.
authors.forename: Yong Doo
authors.initials: YD
authors.lastname: Kim
authors.affiliation: Center for Gas Analysis, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea.
authors.forename: Ji Hwan
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Center for Gas Analysis, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea.
authors.forename: Gwi Suk
authors.initials: GS
authors.lastname: Heo
authors.affiliation: Department of Chemistry, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea.
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Lee
authors.affiliation: Center for Gas Analysis, Division of Metrology for Quality of Life, Korea Research Institute of Standards and Science (KRISS), 267 Gajeong-ro, Yuseong-gu, Daejeon 305-340, Republic of Korea. Electronic address: slee@kriss.re.kr.
authors.forename: Sangil
authors.initials: S
authors.lastname: Lee
keywords: Calibration standard; Climate change; Dimethyl sulphide; Dynamic dilution method