Trace elements inorganic mass spectrometry

An outstanding feature of inorganic mass spectrometry is its determination of precise and accurate isotopic abundances and isotope ratios. Isotopes of the same element (of the same number of protons or atomic number of element, Z) are, by definition, nuclides with different mass m and mass number A (A = Z + N) due to the different number of neutrons (N) in the nucleus. Isotope analyses are of special interest for characterizing the composition of samples with respect to stable and unstable isotopes in quite different concentration ranges - from the analysis of matrix elements down to the trace and ultratrace concentration level.1-9 Of 1700 isotopes, nearly 16 % (264 isotopes) are stable. The chemical elements Tc, Pm, Th, U and the transuranic elements do not possess stable isotopes. 

Selected applications of inorganic mass spectrometry for the multi-element trace analysis of semiconducting materials are summarized in Table 9.12. 

In clinical studies of trace elements in blood and serum using inorganic mass spectrometry, single element clinical applications dominate in the analytical literature 43... 

The mass determination of ionic species (atomic or polyatomic ions) in mass spectrometry is always a comparative measurement, which means the mass of an ionic species is determined with respect to reference masses of elements (or substances) used for mass calibration. The reference mass is thus acquired from the mass unit (m = In = 1/12) of the mass of the neutral carbon isotope (m = 1.66 X 10 kg). A mass calibration is easy to perform in solid-state mass spectrometry if the sample contains carbon (using carbon cluster ions with whole masses, as discussed above). The so-called doublet method was apphed formerly, e.g., ions and doubly charged Mg + forming a doublet at the same nominal mass number 12 were considered, where they are slightly displaced with respect to one another. The doublet method is no longer of relevance in modern inorganic mass spectrometry. Orientation in the mass spectra can be carried out via the matrix, minor and trace elements after mass calibration and by comparing the measured isotopic pattern of elements with theoretical values. 

Environmental monitoring of nuclear contamination, including the determination of the concentration and isotope ratios of long-lived radionuchdes, such as uranium, plutonium isotopes, thorium, Np, Se, Sr, I and others, at trace and ultratrace levels, is a fast growing and fascinating application field for inorganic mass spectrometry." " Among the environmentally important radionuclides, I, Sr, uranium and transuranium elements are of special importance. For example, the natural I inventory in the atmosphere, hydrosphere and biosphere has been estimated to be about 263 kg. ... 

Walczyk, T. (2001) The potential of inorganic mass spectrometry in mineral and trace element nutrition research. Fresenius J. Anal. Chem., 370, 444-453. 

Both the reliable determination of isotope ratios and the quantitation of trace elements generally accompanied by complete destmction of all molecular entities. Opposed to what is normally desired in organic and bio-organic mass spectrometry, ionization methods in inorganic mass spectrometry therefore use conditions which erase any molecular stmcture, i.e., inorganic mass spectrometry particularly employs high temperature plasmas to achieve atomization prior to ionization and mass analysis [27]. Furthermore, ion-neutral reactions need to be suppressed or their products destroyed in order to ensure isotopic patterns free from interferences with isobars [28,29]. 

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