Isotope ratio mass spectrometry applications

Macrocyclic Compounds in Analytical Chemistry. Edited by Yury A. Zolotov Surface-Launched Acoustic Wave Sensors Chemical Sensing and Thin-Film Characterization. By Michael Thompson and David Stone Modern Isotope Ratio Mass Spectrometry. Edited by T. J. Platzner High Performance Capillary Electrophoresis Theory, Techniques, and Applications. Edited by Morteza G. Khaledi... 

Selected applications of isotope ratio monitoring technique in mass spectrometry to geochemistry, biology, medicine and other areas of science are described. It was shown that gas isotope ratio mass spectrometry has greatly increased our understanding of the biogeochemical cycles of C, N, S and H2O in natural and agricultural ecosystems. 

Deuterium nmr spectroscopy has been utilized for the last decade to determine large (primary deuterium) KIEs in reactions with isotopes present at the natural abundance level (Pascal et al., 1984,1986 Zhang, 1988). A great advantage of this approach is that labelled materials do not have to be synthesized. Neither is there any need for selective degradation procedures, which are often necessary to produce the molecules of low mass, e.g. C02, acceptable for isotope ratio mass spectrometry. Moreover, the KIEs for several positions can be determined from one sample. However, until quite recently the relatively low precision of the nmr integrations that are used for the quantitative assessment of the amount of deuterium at specific molecular sites has limited the applicability of this technique for determining small (secondary deuterium) KIEs. 

Platzner, I.T. Applications of Isotope Ratio Mass Spectrometry, in Modem Isotope Ratio Mass Spectrometry, John Wiley Sons Chichester, 1997 pp. 403-447. Beavis, R.C. Chemical Mass of Carbon in Proteins. Anal. Chem. 1993, 65,496-497. Carle, R. Isotopen-Massenspektrometrie Grandlagen und An-... 

Of all the different mass spectrometric techniques for isotope analysis (such as ICP-MS, LA-ICP-MS, TIMS, GDMS, AMS, SIMS, RIMS and isotope ratio mass spectrometry of gases), the greatest proportion of pubhshed papers today concern ICP-MS with single and multiple ion collection.19 Due to its benefits, ICP-MS has now become a widely accepted method for isotope analysis and allows isotope ratios to be measured in a short time with good accuracy and precision.9,19,75 78 As discussed above, as a powerful and universal tool, ICP-MS has opened up new applications for isotope ratio measurements of elements with a high first ionization potential, which are difficult to analyze with TIMS (such as Mo, Hf, Fe). Of all the heavy metals studied, uranium was favoured by ICP-MS and LA-ICP-MS. 

An important application of isotope ratio mass spectrometry is geochronology, which is based on the decay of a radioactive nuclide (e.g., 87Rb,187 Re or 238U) to a stable isotope. The total number of daughter atoms Dt at time t is then equal to the sum of the daughter atoms formed due to the radioactive decay and the number of primordial daughter atoms (D0) at time t = 0 ... 

The nuclear area is one that has been heavily dependent upon isotope ratio mass spectrometry performed by thermal ionization. Applications in this area are among the major reasons for the continued push to analyze smaller and smaller samples. There are two primary reasons for this (1) maximum practicable reduction of the hazards associated with radioactivity and (2) presence of often only a very small amount of the target element available. Areas addressed include evaluation of uranium enrichment processes [86], isotopic analysis of transuranium elements (all elements through einsteinium have been analyzed) [87], and environmental monitoring for release of uranium and other actinides [88,89]. This last area has received renewed emphasis in the wake of the Gulf War [90]. 

The main application of the instrument will be for tracer kinetic and pharmacological measurements in biomedical studies. Essentially, C IRMS is an alternative technique to C Isotope Ratio Mass Spectrometry ( C IRMS), which is widely accepted within the biomedical community. C IRMS is at least 1(X)-1000 times more sensitive than C IRMS. This allows, for example, that the kinetics of C-labelled enzymes, aminoacids or carcinogens can be studied in the human body at levels that are comparable to actual environmental exposure. 

Fig. 6.14 Schematic diagram of a multi-dimensional gas chromatographic-pyrolysis-isotope ratio mass spectrometry (MDGC-P-IRMS) device. After [210] with kind permission of the American Chemical Society. For application see Fig. 6.20...

Brenna JT. High-precision gas isotope ratio mass spectrometry recent advances in instrumentation and biomedical applications. Acc Chem Res 1994 27 340-346. 

Different protein-based methods have been reviewed for species identification in milk and dairy products, and for characterization of cheese maturity, such as electrophoretic, chromatographic, and immunological techniques (11, 12). In addition to new developments in these techniques, the interdisciplinary and dynamic nature of milk product analysis is being enhanced by the application of disciplines already used to analyze other foodstuffs. Among them, capillary electrophoresis (CE), polymerase chain reaction, and isotope ratio mass spectrometry are just gaining popularity for solving dairy authenticity problems (13-15). 

This chapter provides an overview of mass spectrometer function and operation. It describes specific instrument types with demonstrated or potential application for measuring radionuclides and surveys the application of these instruments to radionuclide detection. Finally, it discusses the circumstances under which use of mass spectrometers is advantageous, the type of mass spectrometer used for each purpose, and the conditions of sample preparation, introduction and analysis. Its perspective is from a national laboratory active in environmental and non-proliferation monitoring. It emphasizes isotope ratio measurements, but mass spectrometric measurements also provide isotope mass information. Several recent books describe elemental and isotope ratio mass spectrometry in far greater detail than is presented here (Barshick et al., 2000 De Laeter, 2001 Montaser, 1998 Nelms, 2005 Platzner, 1997 Tuniz et al., 1998). High-resolution mass spectrometry forms the basis of the mass scale used for elemental and isotopic masses (Coplen, 2001), but this application of MS falls outside the scope of this chapter. 

Mass spectrometric approaches are also very useful for the measurement of stable isotopes in drug metabolism studies. The application of MS to the quantitative measurement of stable isotope has been limited due to the high cost and sophistication of the instruments necessary for stable isotope enrichment studies. Nonetheless, recent improvements in instrument design and performance, as well as computer software for instrument control, data acquisition, and analysis, have increased the sensitivity and reliability of stable isotopic enrichment studies. These new MS instruments, including continuous-flow isotope ratio mass spectrometry (CF-IRMS) and HPLC-chemical reaction interface mass spectrometry (HPLC-CRIMS) are increasingly less expensive, easier to operate, and accessible for mass balance/ metabolite identification studies with stable isotopes. 

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