GIRMS, gas isotope ratio mass spectrometry
, IRMS, infrared mass spectrophotometry.
Confirming testosterone administration by isotope ratio mass spectrometry
analysis of urinary androstanediols.
Isotope ratio mass spectrometry
is a specialized magnetic sector mass spectrometry technique designed to measure isotopes.
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).