Page 36 - Inorganic Mass Spectrometry : Fundamentals and Applications

26 Smith

preparation, elimination of contamination, and calibration of the mass spectrome-
ter all need to be meticulously addressed. All sources of bias must be identified
and corrected. This often requires making synthetic mixtures of chemically pure
and isotopically pure (as nearly as possible) enriched isotopes. Very few laborato-
ries have the interest, the ability, and the support to perform such ~easurements.
DeBievre and Peiser have described the history of, and some of the issues
involved in, atomic weight ~easurements [ 1041. Recent determi~ations of atomic
weights using positive thermal ionization include those for tin [ 1051, europium
[106], iron [10’7], antimony [108], and titanium [log]. This subject and others
associated with metrology have been extensively treated in a review by De Laeter
et al. [110].

Thermal ionization mass spectrometry is an exceptionally valuable analytical tool.
Its combinatio~ of high precision and high sensitivity makes it applicable in a
wide variety of situations in which isotopic ratios are sought. In conjunction with
isotope dilution, it provides quantitative analyses that are usually of higher quality
than those yielded by any other method.
Isotope ratios provide insight into the physical and chemical processes that
cause alteration of their values. Their application is expanding as analytical
procedures become more sophisticated and sensitive, and as the extent of scientific
knowledge increases. As in many fields, much work done today would have been
impossible a few years ago. With the advent of multicollector inductively coupled
plasma (ICP) mass spectrometers, it is probable that routine use of thermal
ionization will diminish, but it seems that it will always play a role in applications
in which utmost sensitivity is required.

1. IUPAC Com~ssion on Atomic Weights and Isotopic Abundances. Pure Appl.

2. Faure, G. Principles of Isotope Geology, 2nd Edition, John Wiley & Sons, New
York, 1986.
3. De Laeter, J. R. Mass. Spectrom. Rev. 1996, 15, 261.
4. Nusko, R.; Heurnann, K. G. Fresenius J. Anal. Chem. 1997, 357, 1050.
5. Eisenhut, S.; Heumann, K. G. Fresenius J. Anal. Chem. 1996, 354, 903.
6. Eagles, J.; Fairweathertait, S. J.; Portwood, D. E.; Self, R.; Gotz, A,; Heumann, K. G.
Anal. Chem. 1989, 61, 1023.
7. Gotz, A,; Heumann, K. G. Fresenius J. Anal. Chern, 1987, 326, 11 8.
8. Heumann, K. 6. Int. J. Mass Spectrorn. Ion Processes 1992, 118, 119, 575.