Work

A new look at the sorption kinetics in reference gas standards

Year: 2023

Type: article

Abstract: The preparation of calibration gas mixtures in cylinders using the gravimetric method (ISO 6142-1) has enabled the production of a wide range of mixtures down to the pmol/mol level with low uncertainties reaching 0.01% relative and beyond. The gravimetric method has limited use however for reactive components that adsorb on the cylinder wall or valve. For such components the adage ‘what comes in = what comes out’ no longer holds. To quantify gas losses in cylinders due to adsorption on the inner surfaces, two methods are typically used: by comparison against other gas mixture preparation methods (e.g. dynamic methods) or by decanting part of a mixture in an identical cylinder followed by cross-comparison. Here we present a new method to elucidate the sorption dynamics based on the use of isotopes (here 12C-methanol and 13C-methanol isotopes). The amount fraction evolution of both isotopes in gas phase is followed in time using laser spectroscopic methods. This way, the kinetics of desorption (mainly 13C-methanol) and adsorption (12C-methanol) can be followed in time. In this paper we will present the results from a pilot study on methanol mixtures at trace amount fractions prepared in different cylinder materials and treatments.

Source: Measurement Science and Technology

DOI: 10.1088/1361-6501/ace9ee

Authors: S T Persijn, A Baldan

Institution: VSL National Metrology Institute

Language: English

Topic: Scientific Measurement and Uncertainty Evaluation

Subfield: Instrumentation

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,075

Funder: European Association of National Metrology Institutes