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  • Quantification of the imperfectness of the molecular flow conditions of the gas entering the mass spectrometer ion source for ionization, Exemplified for CO2 isotope amount ratio measurements

Abstract

A new model to describe the gas flow status inside the gas mass spectrometer (MAT271) inlet system has been developed and applied to the latest isotope amount ratio measurements. Starting from the consideration that the gaseous sample flow in the inlet system towards the ion source is a major contributor to the total combined uncertainty on gaseous isotope amount ratio measurements, especially for this particular instrument. The theoretical model elaborated here assumes a transitional flow regime - a mixing between molecular and viscous flow - and defines a mathematical procedure for treatment of the measurement data in order to quantify the viscous flow contribution in the gas flow. The model is entirely suited for the highly specific working conditions in this instrument being an IRMM modified MAT 271 IRMS to perform absolute isotope amount ratio measurements on gas sample. This model could be also applied to data obtained from other IRMS instruments with adequate adaptations. This quantification of the imperfectness of the gas flow to the ion source is materialized as a "viscous factor" and will affect as a correction directed to the data treatment for all isotope amount ratio measurements performed via this instrument. A validation of the elaborated model has been demonstrated to a series of CO2 measurements in calculating the isotope amount ratios of carbon and oxygen from measurements of the ion current ratios. These results obtained are discussed in the paper.

Additional information

Authors: VALKIERS S, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);VARLAM M, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);KUEHN H, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE)
Bibliographic Reference: EUR 22676 EN (2007), various paging. Free of charge
Availability: Katalogue Number: LA-NA-22676-EN-C The PDF version can be downloaded from: http://bookshop.europa.eu
ISBN: ISBN 978-92-79-03346-9
Record Number: 200819809 / Last updated on: 2008-05-05
Category: PUBLICATION
Original language: en
Available languages: en
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