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 abundance of the light stable isotopes of C, O, H, N, S, (and much less frequently, 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 molecular species (CO2, N2, H2, SO2, CO). The main applications were in the characterization and mass balance of the various geological cycles which couple the hydrosphere, the lithosphere, and the atmosphere, Systematic applications of stable isotope methodology to the biosphere had to await the coupling of gas chromatography (GC) with IRMS, which allowed the exquisite chemical resolving power of the GC to be hyphenated with the extraordinary precision of the IRMS.