Chapter 35 - Glow Discharge Mass Spectrometry: Fundamentals and Potential Applications in Stable Isotope Geochemistry

Abstract

This chapter describes the theory, application and practical aspects of a direct-sampling ion source similar to secondary ion mass spectrometry (SIMS), but not well known to the geological community that is the glow discharge. The application of glow discharge mass spectrometry (GDMS) in the Geosciences is limited largely to the elemental analysis of soils, meteorites, and ceramics. Glow discharge (GD) ion sources sputter the sample's surface, and thereby permit direct atomization, ionization and analysis. It is a mechanically simple, highly efficient ion source for mass spectrometry and optical spectroscopy. Commercially built GDMS instrumentation includes single-collector, double-focusing mass spectrometers designed for rapid determinations of trace and major elements at high mass-resolving powers. Its direct solid sampling capability and very low matrix dependence makes GDMS a convenient technique for the rapid analysis of highly refractory materials, or for samples where compositional depth profiling is needed. However, very little work is done to optimize GDMS for routine use in isotope ratio determinations. Promising developments includes the development of GD ion sources fitted to compact, robust time-of-flight mass analyzers capable of isotope ratio precision and accuracy.