Trace determination and isotopic analysis of the elements in life sciences by mass spectrometry

Abstract

The main ionization methods in a mass spectrometer for isotope ratio determinations of the elements are discussed in this review. These methods are thermal ionization, spark source, electron impact, inductively coupled plasma and field desorption. As concerns thermal ionization, electron impact and field desorption, a survey of the possibilities of isotope analyses in the periodic table of the elements is given. Besides kinetic studies, trace element determination by isotope dilution technique is the main application for isotope ratio measurements of the elements. The definitive method, isotope dilution mass spectrometry, is discussed as a potential tool for achieving accurate and precise trace analyses. Using field desorption mass spectrometry, one example of calcium kinetics in man and one example of thallium trace determination in an animal tissue are given. Other metal trace analyses with the isotope dilution technique are presented for biological and medical samples using positive thermal ionization mass spectrometry. Negative thermal ions are formed for the mass spectrometric analysis of non-metals and non-metal compounds in food samples, e.g. for iodine and nitrate in milk powder. Preliminary results with the isotope dilution technique are presented for a new quadrupole thermal ionization mass spectrometer which is a low-cost instrument and can be easily handled.

Contribution of mass spectrometry to assess quality of milk‐based products

“…Mass spectrometry detection was also used for the analysis of trace elements with the potential of better sensitivity and multi‐elemental analysis. A review article described examples of trace analyses by isotope dilution mass spectrometry techniques with various ionization sources such as thermal ionization, spark source, electron impact, inductively coupled plasma, and field desorption (Heumann, 1985). Indeed, the use of stable isotopes for element investigations can be either for labeling experiments, determination of natural isotope variations, kinetic studies, or for a more accurate quantitative analysis.…”

Application of Isotope Dilution to Ion Trap Gas Chromatography/Mass Spectrometry

“…Isotope dilution mass spectrometry (IDMS) is a well-established technique for accurately determining the concentration of a target element in a sample of unknown concentration. − In practice, a known amount of a spike of known isotopic composition is added to a known amount of a sample of known isotopic composition; the isotopic composition of the spike and sample must be different. Once isotopic equilibrium is established between the spike and sample, the ratio of the spike and sample isotopes in the mixture is measured by mass spectrometry; the application of the isotope dilution equation (see below) provides the final concentration.…”