Evolution and revolution in instrumentation for plasma-source mass
spectrometry*
Gary M. Hieftje1,**, James H. Barnes1, Ole A. Grøn1, Andrew
M. Leach2, Denise M. McClenathan1, Steven J. Ray1, David A. Solyom3,
William C. Wetzel1, M. Bonner Denton4, and David W. Koppenaal5
1Department of Chemistry, Indiana University, Bloomington,
IN 47405, USA; 2Present address: Department of Chemistry, Stanford University,
Stanford, CA 94305, USA; 3Present address: Honeywell FM&T, Kansas
City, MO 64141-6159, USA; 4Department of Chemistry, University of Arizona,
Tucson, AZ 85724, USA; 5Pacific Northwest National Laboratory, Richland,
WA 99352, USA
Abstract: Plasma-source mass spectrometry, usually in the form
of inductively coupled plasma mass spectrometry (ICP-MS), has matured
into a widely accepted method for ultra-trace multielemental analysis.
However, the method exhibits shortcomings. For example, it does not
provide adequate precision for isotope ratio measurements if many isotopes
are to be determined. Moreover, isobaric overlaps (spectral interferences)
can be very troublesome in some situations. Similarly, matrix interferences
can adversely affect many determinations. Yet, it is in the area of
high-speed transient measurements that ICP-MS perhaps suffers its greatest
weakness. When sampling devices such as flow injection, laser ablation,
electrothermal vaporization, or chromatography are employed, the user
must choose between broad elemental or isotopic coverage and signal-to-noise
ratio (S/N). In turn, compromised S/N means lower precision or poorer
detection limits. Here, new instrumentation aimed at overcoming these
limitations will be described. One system, based on a time-of-flight
mass spectrometer, provides excellent detection limits, resolving power
better than commercial quadrupole mass filters, precision of at least
0.02% rsd in a ratioing mode, and extraordinarily high speed for use
with transient sampling devices. The second instrument is based on a
sector-field mass spectrometer but, unlike other such units, is equipped
with a focal-plane array detector. So equipped, the system can detect
a broad mass range at once.
*Lecture presented at the IUPAC International Congress
on Analytical Sciences 2001 (ICAS2001), Tokyo, Japan, 6-10 August 2001.
Other presentations are published in this issue,
pp. 1555-1623.
** Coresponding Author
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