Advancing the capabilities of a glow-discharge sector-field mass spectrometer

Abstract

The improved analytical capabilities of a glow-discharge Mattauch–Herzog mass spectrograph are presented. The glow discharge is a desirable analytical source because of its simplicity and direct solids analysis capabilities. The Mattauch–Herzog double-focusing sector geometry produces a linear focal plane, in contrast to the curved focal region common to most sector instruments. Placing an array detector along this focal plane allows simultaneous and continuous acquisition of data over an entire mass range, whereas an ordinary sector instrument must scan this same range. In this paper, the present capabilities of the mass spectrograph with a glow-discharge source are presented. Due to present-day array-detector limitations, mass spectral acquisition was performed with an electron multiplier by scanning the magnetic field. Ultimately, a suitable array detector will be incorporated and the data shown here will serve as a reference for future array-detector data. Also considered here is the compatibility between the mass spectrograph and a microsecond pulsed glow discharge source. The pulsed source produces analyte and bulk plasma ions at different periods within the pulse cycle. This feature, coupled with gated ion optics, enhances the determination of species in close mass spectral proximity to bulk plasma ions. This capability will be particularly useful when an array detector is used because of the inherent susceptibility of such detectors to accidental overexposure from sample-matrix and plasma ions.