Page 282 - Inorganic Mass Spectrometry - Fundamentals and Applications

268 Marcus

~~rn~rnin
Total-ion (a, c) and single-ion monitoring (b, d) temporal profiles of Al,0, Sam-
ples compacted (1 :S) in a copper matrix using Ne b) and Ar (c, d) discharge gases. (From
(a,
Ref. 45.)

capabilities, a l-hour 200°C in vacuo bakeout was employed drive off adsorbed
to
water vapor. GD-MS is a very attractive alternative to ICP-MS in this application
because of the great dificulty and cost of dissolving the cordierite sample matrix.
The precision and accuracy of the methods (using Bi as an internal standard) were
both found to be better than 10% RSD, quite acceptable values for the automotive
industry. The increasing usage of zirconium in these catalysts poses a challenge
because isotopes of zirconium oxides interfere with palladium isotopes. A mathe-
matical model allows stripping of the oxide contributions and improvement in ac-
curacy of palladium determinations by CD-MS.
Two related methods of nonconductive sample preparation should be men-
tioned here. The first, described by Battagliarin and coworkers [46], involves the
use of a heated die assembly in which molten indium is added to the oxide pow-
der sample. Continued heating and applied pressure cause the indium to flow
through the interstices of the powder such that the sample (GeO,) becomes dis-
persed in the metal. On cooling, the metal pin is easily removed from the die. The
method produces very stable plasmas (-3% RSD) after 50-min. presputtering times,
and a favorable sample-to-sample reproducibility (~5% RSD). The authors state
that the use of molten indium has promise as a general analytical strategy. sec-
The
ond method does not actually involve the sputtering of a nonconductive sample.
Barshick and Harrison [4'7] have described the use of a l-rnJ pulse excimer laser
to ablate compacted UO, samples into a pulsed glow discharge sustained at a cop-
per pin electrode. In this way, the oxide material is introduced into the GD plasma,