Mass Spectrometer

Abstract

An isotope ratio mass spectrometer has an ion source, a static field mass filter, a reaction cell to induce a mass shift reaction, and a sector field mass analyser for spatially separating ions from the reaction cell according to their m / z. A detector platform detects a plurality of different ion species separated by the sector field mass analyser. The static field mass filter has a first Wien filter that deflects ions away from a longitudinal symmetry axis of the spectrometer in accordance with the ions' m / z, and a second Wien filter that deflects ions back towards the longitudinal symmetry axis in accordance with the ions' m / z. An inverting lens is positioned along the longitudinal axis between the Wien filters to invert the direction of deflection of the ions from the first Wien filter. The static field mass filter provides high transmission and improved spectrometer sensitivity. The first and second Wien filters permit simple tuning.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a National Stage application filed under 35 USC § 371 of International Patent Application No. PCT / EP2019 / 056884, filed on Mar. 19, 2019. PCT Application No, PCT / EP2019 / 056884, claims priority to GB 1804386.9, filed Mar. 19, 2018, both of which are incorporated by reference herein in their entirety.FIELD OF THE INVENTION[0002]This invention relates to a static field mass filter for a mass spectrometer and a mass spectrometer, in particular, but not exclusively, for isotope ratio mass spectrometry (IRMS).BACKGROUND OF THE INVENTION[0003]Mass spectrometers are used to analyse the m / z ratios of ions which have been generated by an ion source from a sample. Before analysis, the ions might be further exposed to other processes in one or more reaction cells. Further mass filters may be used to reduce the amount of analysed ions by selecting only ions in a specific m / z range of a m / z window. Such a mass filter is arranged betw...

AI Technical Summary

Benefits of technology

The static field mass filter technology presents several advantages compared to RF based mass filter technology. Firstly, it works perfectly well with wide aperture high ion beam energy ion optics which ensures high transmission and sensitivity of the complete mass spectrometer. Secondly, it allows for easy tuning along the path of the ions by applying internal normalisation algorithms for mass fractionation correction. Thirdly, it is highly stable and can withstand small drifts of instrument parameters. Finally, it uses high ion energy ion optics that provide improved focusing conditions and higher robustness against space charge. The ions are spread over their mass-to-charge ratio in the direction transverse to the flight direction, which avoids the mixing of flight paths of ions.

Problems solved by technology

This leads to a flat transmission of ions across a selected mass-to-charge ratio range and small deviations in system tuning do not change the measured isotope ratio in an unpredictable way.

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