High-precision continuous-flow isotope ratio mass spectrometry (original) (raw)

1997, Mass Spectrometry Reviews

Although high-precision isotope determinations are routine in 1997), nitrification rates in forests (Starle & Hart, 1997), many areas of natural science, the instrument principles for their biodegradation (Aggarwal et al., 1997), and the climate measurements have remained remarkably unchanged for four history of the earth (Schoell et al., 1994). In ecology and decades. The introduction of continuous-flow techniques to isobiogeochemistry alone, two volumes (Ehleringer & Runtope ratio mass spectrometry (IRMS) instrumentation has predel, 1988; Ehleringer, Hall, & Farquhar, 1993) and at least cipitated a rapid expansion in capabilities for high-precision one meeting (Griffiths, 1996) devoted to applications of measurement of C, N, O, S, and H isotopes in the 1990s. Elemenhigh-precision isotope measurements have appeared in the tal analyzers, based on the flash combustion of solid organic last few years. Isotope ratio MS (IRMS) has penetrated samples, are interfaced to IRMS to facilitate routine C and N areas of biological science to a greater degree than organic isotopic analysis of unprocessed samples. Gas/liquid equilibramass spectrometry. In addition to studies of natural varitors have automated O and H isotopic analysis of water in untreated aqueous fluids as complex as urine. Automated cryo-ability, high-precision isotope measurements facilitate a genic concentrators permit analysis at part-per-million concennumber of tracer techniques in the biomedical sciences, trations in environmental samples. Capillary gas chromatograincluding the doubly labeled water method for energy exphy interfaced to IRMS via on-line microchemistry facilitates penditure (Schoeller et al., 1986), protein turnover studies compound-specific isotope analysis (CSIA) for purified organic (Chapman et al., 1990), fat metabolism (Brenna, 1997), analytes of 1 nmol of C, N, or O. GC-based CSIA for hydrogen and a range of breath tests with the potential to revolutionand liquid chromatography-based interfaces to IRMS have both ize clinical diagnostic testing (Ghoos, Rutgeerts, & van been demonstrated, and continuing progress promises to bring Trappen, 1995). these advances to routine use. Automated position-specific iso-The early history of MS was dominated by physical tope analysis (PSIA) using noncatalytic pyrolysis has been measurements to establish the nominal, terrestrial isotopic shown to produce fragments without appreciable carbon scramabundances of the elements. The early parabola method bling or major isotopic fractionation, and shows great promise for intramolecular isotope ratio analysis. Finally, IRMS notation