Two new portable generators to dynamically produce SI-traceable reference gas mixtures for reactive compounds at atmospheric concentration

Céline Pascale, METAS

New facilities are currently being developed at METAS to dynamically generate reference gas mixtures for a variety of reactive compounds, at concentrations measured in the atmosphere and in a SI-traceable way. This work is done in the framework of the EMRP projects KEY-VOCs and HIGHGAS as well as METAS’ AtmoChemECV project. We present two new portable generators for the realisation of such standards for volatile organic compounds (VOCs) such as limonene, alpha-pinene, MVK, MEK, in the nmol/mol range (ReGaS-2), and fluorinated gases (F-gases, i.e. containing fluorine atoms) in the pmol/mol range (ReGaS-3). These two portable generators have been designed and manufactured at METAS.

The method is based on permeation and dynamic dilution: one permeator containing a pure substance (for example pure limonene) is kept into a permeation chamber with a constant temperature, pressure and gas flow. The mass loss is precisely calibrated before and after hand using a magnetic suspension balance. The carrier gas is purified beforehand from the compounds of interest to the required level, using commercially available purification cartridges. The permeation chamber of the portable generator has multiple individual cells allowing the generation of mixtures up to 5 different components if needed. This primary mixture is then diluted to reach the required amount of substance fraction. All flows are piloted by mass flow controllers, making the production process flexible and easily adaptable to generate the required concentration. All parts of ReGaS-2 in contact with the gas mixture are passivated using coated surfaces, to reduce adsorption/desorption processes as much as possible.

These two portable generators could be used anywhere in a lab or in the field. Moreover the presented technique can be adapted and applied to a large variety of molecules (e.g., NO2, BTEX, CFCs, HCFCs, HFCs and other refrigerants) and is particularly suitable for gas species and/or concentration ranges that are not stable in cylinders.

Pen Profile

I finished my Master in Chemical Engineering in 2011 at the polytechnic school of Lausanne, in Switzerland. I began to work straight away at METAS, the Swiss federal Institute of Metrology, in the Gas Laboratory.
Since 6 years, I am in charge of the production of reference gas mixtures at ambient level concentrations for reactive gases. I am experienced in the dynamic production of reactive gases, such as NO, NO2, and VOC, using permeation and dilution methods. I also have expertise in uncertainty budget assessment.
Since November 2014, I am co-managing an interne new R&D project aiming at improving the reference gas mixtures for Essential Climate Variables defined by GCOS in 2010.Those new certified reference materials will improve the quality of the actual measurements of air monitoring stations giving them traceability to national standard and a well-defined uncertainty. This will lead to international data recognition.

As responsible for the dissemination of standards, METAS takes part in the GAS2017 Symposium to present the new developments and calibration possibilities of the Gas Laboratory.

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