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
Equivalence was defined by the percentage of agreement for positive and negative cases based on gas isotope ratio mass spectrometry results of at least 95%, and the lower limit of the 95% confidence interval was based on a percentage of agreement of at least 90% for positive cases.
GIRMS, gas isotope ratio mass spectrometry, IRMS, infrared mass spectrophotometry.
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).
A) individual substance isotope analysis of 13C/12C, 15N/14N, H / D isotope ratios of organic molecules by means of gas chromatography / isotope mass spectrometry (gas chromatography isotope ratio mass spectrometry, GC / IRMS), (b) measurements of the 13C/12C, 15N / 14N, H / D isotope ratios on the same isotope mass spectrometer by means of combustion of sediment / organic components / filters and separation of gases by chromatographic column before the inlet to the isotope mass spectrometer.
Androstanediol and 5-androstenediol profiling for detecting exogenously administered dihydrotestosterone, epitestosterone, and dehydroepiandrosterone: potential use in gas chromatography isotope ratio mass spectrometry.