Gas source mass spectrometry

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Gas source mass spectrometry (GS–MS) is the name given to instrumentation used for the determination of stable isotopic compositions of those particular elements that can be analyzed in a gaseous form. It differs from thermal ionization mass spectrometry (q.ν.) where the elements of interest are admitted to the instrument in a solid form. GS–MS is principally employed for the analysis of hydrogen (as H2), carbon (as CO2), nitrogen (as N2), oxygen (as CO2, or O2) and sulfur (as SO2, or SF6). GS–MS is also used for the analysis of chlorine (as CH3Cl) and silicon (as SiF4), but these applications are comparatively rare. A further suite of elements, the noble gases (He, Ne, Ar, Kr and Xe), are also analyzed using a form of GS–MS, but this is a highly specialized variety and will not concern us here (the interested reader is referred instead to 40Ar/39Ar dating).

In a geologic context the species that can be determined using-GS–MS often have a certain commonality of occurrence ...