The Gas Sensing Metrology Group at NIST provides accurate, stable gaseous standards for use in va... more The Gas Sensing Metrology Group at NIST provides accurate, stable gaseous standards for use in various types of emissions testing and environmental monitoring. The group develops and maintains the highest level of primary gas standards, which provide direct traceability to the International System of Units (SI). This traceability is then realized through the certification and dissemination of reference gas standards, such as NIST Standard Reference Materials (SRMs). Gas mixture SRMs are produced by a specialty gas company, analyzed by NIST against primary gas standards, and sold to customers to provide traceability for their gas measurements. This document provides an overview of the gas metrology program at NIST, and describes the general procedures which are used to develop and certify gas mixture SRMs.
Exhaled breath is a non-invasive, information-rich matrix with the potential to diagnose or monit... more Exhaled breath is a non-invasive, information-rich matrix with the potential to diagnose or monitor disease, including infectious disease. Despite significant effort dedicated to biomarker identification in case control studies, very few breath tests are established in practice. In this topical review, we identify how gas standards support breath analysis today and what is needed to support further expansion and translation to practice. We examine forensic and clinical breath tests and discuss how confidence has been built through unambiguous biomarker identification and quantitation supported by gas calibration standards. Based on this discussion, we identify a need for multicomponent gas standards with part-per-trillion to part-per-million concentrations. We highlight National Institute of Standards and Technology gas standards developed for atmospheric measurements that are also relevant to breath analysis and describe investigations of long-term stability, chemical reactions, an...
Main text At the highest metrological level, ammonia gas standards are commonly prepared gravimet... more Main text At the highest metrological level, ammonia gas standards are commonly prepared gravimetrically as Primary Standard Mixtures or using a dynamic standard. This international key comparison addressed the measurement of the amount fraction ammonia in nitrogen, to support calibration and measurement services for mainly environmental applications. The nominal amount fraction was 14 μmol mol-1. The results in this Track C key comparison on the composition of biogas are generally good. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
There are many gas phase compounds present in the atmosphere that affect and influence the earth&... more There are many gas phase compounds present in the atmosphere that affect and influence the earth's climate. These compounds absorb and emit radiation, a process which is the fundamental cause of the greenhouse effect. The major greenhouse gases in the earth's atmosphere are carbon dioxide, methane, nitrous oxide, and ozone. Some halocarbons are also strong greenhouse gases and are linked to stratospheric ozone depletion. Hydrocarbons and monoterpenes are precursors and contributors to atmospheric photochemical processes, which lead to the formation of particulates and secondary photo-oxidants such as ozone, leading to photochemical smog. Reactive gases such as nitric oxide and sulfur dioxide are also compounds found in the atmosphere and generally lead to the formation of other oxides. These compounds can be oxidized in the air to acidic and corrosive gases and contribute to photochemical smog. Measurements of these compounds in the atmosphere have been ongoing for decades t...
Main text The growing awareness of climate change, and continuing concerns regarding tropospheric... more Main text The growing awareness of climate change, and continuing concerns regarding tropospheric and stratospheric chemistry, will require future measurements and standards for compounds linked to these issues. To globally monitor and control the emissions of these species in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. This report describes the results of a key comparison for several important monoterpene species, which are relevant to atmospheric chemistry and climate. The comparison samples include α-pinene, 3-carene, R-limonene and 1,8-cineole in a nitrogen matrix gas, at a 2.5 nmol mol-1 amount of substance fraction. The objective of this key comparison is to evaluate the participants' capabilities to measure trace level monoterpenes using their own calibration techniques. KEY WORDS FOR SEARCH VOCs, terpenes, metrology, gas standards Main text To reach the main text of this paper,...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The Gas Sensing Metrology Group at NIST provides accurate, stable gaseous standards for use in va... more The Gas Sensing Metrology Group at NIST provides accurate, stable gaseous standards for use in various types of emissions testing and environmental monitoring. The group develops and maintains the highest level of primary gas standards, which provide direct traceability to the International System of Units (SI). This traceability is then realized through the certification and dissemination of reference gas standards, such as NIST Standard Reference Materials (SRMs). Gas mixture SRMs are produced by a specialty gas company, analyzed by NIST against primary gas standards, and sold to customers to provide traceability for their gas measurements. This document provides an overview of the gas metrology program at NIST, and describes the general procedures which are used to develop and certify gas mixture SRMs.
Exhaled breath is a non-invasive, information-rich matrix with the potential to diagnose or monit... more Exhaled breath is a non-invasive, information-rich matrix with the potential to diagnose or monitor disease, including infectious disease. Despite significant effort dedicated to biomarker identification in case control studies, very few breath tests are established in practice. In this topical review, we identify how gas standards support breath analysis today and what is needed to support further expansion and translation to practice. We examine forensic and clinical breath tests and discuss how confidence has been built through unambiguous biomarker identification and quantitation supported by gas calibration standards. Based on this discussion, we identify a need for multicomponent gas standards with part-per-trillion to part-per-million concentrations. We highlight National Institute of Standards and Technology gas standards developed for atmospheric measurements that are also relevant to breath analysis and describe investigations of long-term stability, chemical reactions, an...
Main text At the highest metrological level, ammonia gas standards are commonly prepared gravimet... more Main text At the highest metrological level, ammonia gas standards are commonly prepared gravimetrically as Primary Standard Mixtures or using a dynamic standard. This international key comparison addressed the measurement of the amount fraction ammonia in nitrogen, to support calibration and measurement services for mainly environmental applications. The nominal amount fraction was 14 μmol mol-1. The results in this Track C key comparison on the composition of biogas are generally good. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
There are many gas phase compounds present in the atmosphere that affect and influence the earth&... more There are many gas phase compounds present in the atmosphere that affect and influence the earth's climate. These compounds absorb and emit radiation, a process which is the fundamental cause of the greenhouse effect. The major greenhouse gases in the earth's atmosphere are carbon dioxide, methane, nitrous oxide, and ozone. Some halocarbons are also strong greenhouse gases and are linked to stratospheric ozone depletion. Hydrocarbons and monoterpenes are precursors and contributors to atmospheric photochemical processes, which lead to the formation of particulates and secondary photo-oxidants such as ozone, leading to photochemical smog. Reactive gases such as nitric oxide and sulfur dioxide are also compounds found in the atmosphere and generally lead to the formation of other oxides. These compounds can be oxidized in the air to acidic and corrosive gases and contribute to photochemical smog. Measurements of these compounds in the atmosphere have been ongoing for decades t...
Main text The growing awareness of climate change, and continuing concerns regarding tropospheric... more Main text The growing awareness of climate change, and continuing concerns regarding tropospheric and stratospheric chemistry, will require future measurements and standards for compounds linked to these issues. To globally monitor and control the emissions of these species in the atmosphere, it is necessary to demonstrate measurement equivalence at the highest levels of accuracy for assigned values of standards. This report describes the results of a key comparison for several important monoterpene species, which are relevant to atmospheric chemistry and climate. The comparison samples include α-pinene, 3-carene, R-limonene and 1,8-cineole in a nitrogen matrix gas, at a 2.5 nmol mol-1 amount of substance fraction. The objective of this key comparison is to evaluate the participants' capabilities to measure trace level monoterpenes using their own calibration techniques. KEY WORDS FOR SEARCH VOCs, terpenes, metrology, gas standards Main text To reach the main text of this paper,...
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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