In-Line Combustion System for the Measurement of δC-CH in Gas Reference Materials Using Optical Isotope Ratio Spectroscopy.

Measurements of the stable carbon isotope ratio in methane (δC-CH) are used in determining the source of CH emissions on local, regional, and global scales. To achieve the required level of data comparability for atmospheric monitoring networks, accurate gas reference materials of δC-CH in air are required with high levels of reproducibility. We describe a method to determine the δC-CH of CH in synthetic air reference materials reported against the Vienna Pee Dee Belemnite (VPDB) scale.

Step Change in Improving the Accuracy of Nitrous Oxide Reference Materials for Underpinning Atmospheric Composition Measurements.

We have employed a new approach to quantify the amount fraction of nitrous oxide in a synthetic air matrix gas used to prepare high-accuracy reference materials of the same component. Until now, this was the largest contributor to the measurement uncertainty of nitrous oxide in air reference materials at atmospheric amount fractions (∼330 nmol mol), as identified in a recent international comparison. A novel preconcentration method has resulted in a measurement of 363 pmol mol of nitrous oxide in a synthetic air matrix gas with an expanded uncertainty of 27 pmol mol.

Boreas: A Sample Preparation-Coupled Laser Spectrometer System for Simultaneous High-Precision In Situ Analysis of δC and δH from Ambient Air Methane.

We present a new instrument, "Boreas", a cryogen-free methane (CH) preconcentration system coupled to a dual-laser spectrometer for making simultaneous measurements of δC(CH) and δH(CH) in ambient air. Excluding isotope ratio scale uncertainty, we estimate a typical standard measurement uncertainty for an ambient air sample of 0.07‰ for δC(CH) and 0.

Breakthrough in Negating the Impact of Adsorption in Gas Reference Materials.

We have shown that an exchange dilution preparation method reduces the impact of surface adsorption of the target component in high-pressure gas mixtures used for underpinning measurements of amount-of-substance fraction. Gas mixtures are diluted in the same cylinder by releasing an aliquot of the parent mixture. Additional matrix gas is then added to the cylinder.