Evolution and revolution in instrumentation for plasma-source mass spectrometry

Hieftje, Gary M.; Barnes, James H.; Grøn, Ole A.; Leach, Andrew M.; McClenathan, Denise M.; Ray, Steven J.; Solyom, David A.; Wetzel, William C.; Denton, M. Bonner; Koppenaal, David W.

doi:10.1351/pac200173101579

Pure Appl. Chem., 2001, Vol. 73, No. 10, pp. 1579-1588

http://dx.doi.org/10.1351/pac200173101579

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

¹ Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
² Present address: Department of Chemistry, Stanford University, Stanford, CA 94305, USA
³ Present address: Honeywell FM&T, Kansas City, MO 64141-6159, USA
⁴ Department of Chemistry, University of Arizona, Tucson, AZ 85724, USA
⁵ Pacific 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.