A high-accuracy, high-precision form of mass spectrometry used to determine ratios of atomic isotopes in small volumes of gas, which are used in geochemistry, cosmological chemistry, (carbon) dating and tracer studies
The most suitable methods for such studies are isotope-dilution mass spectrometry methods, including gas chromatography-mass spectrometry (GC/MS)  and isotope ratio mass spectrometry coupled with a combustion chamber furnace and GC (GC/C/IRMS) (4).
Androstanediol and 5-androstenediol profiling for detecting exogenously administered dihydrotestosterone, epitestosterone, and dehydroepiandrosterone: potential use in gas chromatography isotope ratio mass spectrometry. Steroids 1997;62:665-73.
However, the use of gas isotope ratio mass spectrometry to measure [sup.2][H.sub.2]O is expensive, requires specialist knowledge for operation and maintenance, and is somewhat tedious because the water is first transformed to hydrogen (3, 4) or equilibrated with hydrogen (5, 6).