Isotope dilution mass spectrometry characterization

Isotope dilution mass spectrometry (cf. (Heumann, 1992 Yu et al., 2002)) has two main requirements. The first is that the element being analyzed must have more than one isotope. The second is to have a well-characterized and pure tracer solution that has a significantly different isotopic composition from the element under analysis. In practice, a known amount of the tracer is added to the sample, which is then treated by any necessary chemical separations before being inserted into the mass spectrometer. The tracer must be isotopically equilibrated with the sample by forcing them into a common valence state, as discussed in Section 4.7. For elements with multiple valence states (such as uranium or plutonium) this is a crucial requirement. Failure to achieve isotopic equilibration will lead to erroneous results. Sample quantitation by isotope dilution can be determined by use of the following general equation ... 

Schaumloffel, D., Prange, A.,Marx, G., Heumann, K. G., andBratter,P. (2002) Characterization and quantification of metallothionein isoforms by capillary electrophoresis-inductively coupled plasma-isotope-dilution mass spectrometry. Anal. Bioanal. Chem., 372,155 3. 

Inductively coupled plasma—mass spectrometry (referred to in this book as ICP-MS), a technique for the elemental chemical characterization of virtually any material, evolved during the late 1990s into a mature analytical procedure. This technique has a variety of characteristics that make it uniquely suited for the solution of chemical analysis problems in many applications. These characteristics include the abihty to precisely identify and measure (quantitate) all elements in the periodic table including the often difficult to analyze refractory elements. In addition to this wide scope of elemental analysis, the technique has the inherent capabihty to perform these determinations in a multielement analysis mode, efficiendy providing comprehensive elemental compositional characterization. The technique also has the powerful ability to measure individual isotopes of the analyte elements, providing a capability that has many useful apphcations ranging from isotope dilution quantitation to stable isotope tracer studies. 

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