Page 251 - Inorganic Mass Spectrometry - Fundamentals and Applications

Isotope ~~lution Mass Spectrometry 237

of some recent publications in which isotope dilution mass spectrometry was used
to good advantage.
One excellent example was the determination of lead in human plasma at
sub-nanogram per milliliter (sub-ppb) levels by Bowins and McNutt [39]. Detec-
tion limits of 16 X g were reported. Use of a 204Pb spike and electrothermal
better
vaporization provided excellent sensitivity and accuracy, with precision than
2% at the 1.3-ngkL level.
Jiang et al. recently reported use of two different sample introduction ap-
proaches to analyze Cu, Cd, and Pb in biological samples through use a multi-
of
element isotopic spike. The first was anodic stripping voltmetry, first adapted
for ICP-MS application by Caruso, Pretty, and coworkers [40-42]; this step
achieves both elemental preconcentration and elimination of the matrix. Jiang et
al. describe optimizing the system for use with isotope dilution and report good
The
agreement (ca. 2%) of their results with certified reference materials [43]. sec-
ond development of this group was using isotope dilution in a system in which an
electrothermal vaporization device converted the sample to the gas phase [44]. A
palladium-treated graphite crucible was used to overcome the excessive volatility
of cadmium. Again good results were obtained from reference materials.
Yoshinaga and Morita used isotope dilution in conjunction with ICP-MS to
measure mercury in biological and environmental samples [45]. The same group
used microwave-induced plasma mass spectrometry the isotope dilution analy-
for
sis of selenium in biological materials 1461. Analysis of nickel via isotope dilution
et
and ICP-MS has been reported by Patriarca al[47].

Isotope dilution mass spectrometry was used in the nuclear area almost from its
inception. Most Department of Energy (DOE) laboratories monitored uranium in
some form or other, whether for process purposes or for evaluation of releases to
the environment. Since this is a relatively mature field, and since the United States
is
has curtailed its development of nuclear power, research in this area much less
active than it used to be.
in
One of the most significant parameters reactor operation is burn-up"i.e.,
the amount of usable fuel consumed. One of the most important uses of this in-
formation is comparison of actual burn-up with predictions computer codes; ac-
of
curate codes are vital to efficient and safe reactor operation. The most commonly
used calculations require knowledge of the isotopic compositions and amounts of
uranium, plutonium, and neodymium [48]. The necessary analyses make the pro-
fuel
cedure both time-consuming and very expensive, especially as spent rods are
cell.
radioactive enough to require that initial operations be performed in a hot Iso-
tope dilution has traditionally been used as means of quantification of all three
the
elements. Green et al. report a thorough analysis of spent fuel rods in which
nanogram quantities of the three elements were analyzed; precision ranged from