Hyphenation of gas chromatographic techniques with isotope ratio mass spectrometry: Present status and future

Isotope ratio mass spectrometers (IRMS) are highly specialized sector field mass spectrometers which are dedicated to a single purpose: high precision and high accuracy measurements of the variations in natural isotopic abund ance of the light stable isotopes of C, O, H, N, S, (and much less frequent ly, Cl, Si, and Se). These mass spectrometers have a fixed array of Faraday collectors and they are built to analyze a very small range of simple mole cular species (CO2, N2, H2, SO2, CO). The main applications were in the cha racterization and mass balance of the various geological cycles which coupl e the hydrosphere, the lithosphere, and the atmosphere, Systematic applicat ions of stable isotope methodology to the biosphere had to await the coupli ng of gas chromatography (GC) with IRMS, which allowed the exquisite chemic al resolving power of the GC to be hyphenated with the extraordinary precis ion of the IRMS.