Page 280 - Inorganic Mass Spectrometry - Fundamentals and Applications

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1 l Mo

Glow discharge:mass spectrometry (GD-MS) spectrum of a rnixture of rare
earth oxides compacted in a tantalum host matrix. Oxide composition 5% by weight in disk,
each element present at 110 ppm. (From Ref. 39.)

100%. As such, a high R value represents the ability to produce analyte ions in
favor of metal oxides. Temporal profiles
of R values vs. time illustrated that the Ti,
Ta and W (known getter) plasmas reached steady-state condition in approximately
l hr, with plateau R values of Ti = -.loo%, Ta = a%, and W = -80%. High R val-
ues could be obtained for carbon (&O%), though a steady state was not achieved
within the first 4 hr of operation. Silver had the lowest R value of the group (as
might be expected), reaching a value of 20% after 3 hr of sputtering.

Three papers set out nicely the range of applicability of the compaction method-
ology in GD-MS. The analysis of soils was evaluated by Smith and coworkers [43]
on a hi~h-resolution VG9000 instrument. Sample pins (1.5-mm diameter, 18-m
length) were formed with a silver host and a 10: 1 (Agsoil) mixing ratio. Two Na-
tional Institute of Standards and Technology (NIST) reference materials were used
to demonstrate the analytical figures of merit. Fifty-one elements were analyzed
in NTST 4355 Peruvian Soil. As in the case of most GD-MS analyses, an internal
reference (Io7Ag) was used to generate ion beam ratios for quantification and all
analytical characterization. After a 20-min presputtering period, the variation in