Acronym in analytical chemistry: GC-irm-MS for gas chromatography—isotope ratio monitoring—mass spectrometry

The term gas chromatography—isotope ratio monitoring—mass spectrometry (GC-irm-MS) was coined in the 1980s in Indiana by John Hayes, Kate Freeman and others for a novel technique they applied in the determination of isotopic compositions of compounds in mixtures of environmental samples [1]. The glossary in Echoes of Life gives the following definition of the GC-irm-MS technique [1]:

A gas chromatograph combined with a combustion interface that burns the separated compounds to CO2, and with a special mass spectrometer that can then measure the relative abundance of isotopes. Used to determine the isotopic composition of individual molecular species.

The acronym is sometimes also written in its all-uppercase form GC-IRM-MS. Synonymously, the acronyms irm-GC/MS and GC-IRMS are in use.

Reference
[1] Susan M. Gaines, Geoffrey Eglington, and Jürgen Rullkötter: Echoes of Life • What Fossil Molecules Reveal about Earth History. Oxford University Press, New York, 2009; see, for example, page 157 and glossary.

Further references to GC-irm-MS applications and results
[2] The graphical representation on page 158 in [1] gives a nice overview of differences of ¹³C isotopic composition found in various groups of organisms, the environment and geologic deposits.

[3] Group of 9 authors: Terrestrial vegetation change inferred from n-alkane σ¹³C analysis in the marine environment. Geochimica et Cosmochimica Acta 1995, 59, pp. 2853-2857.
DOI: 10.1016/0016-7047(95)00160-2.

[4] Bart E. van Dongen, Stefan Schouten and Jaap S. Sinninghe Damsté: Gas chromatography/combustion/isotope-ratio-monitoring mass spectrometeric analysis of methylboronic derivatives of monosaccharides: a new method for determining ¹³C abundances of carbohydrates. Rapid Communications in Mass Spectrometry 2001, 15 (7), pp. 496-500.
DOI: 10.1002/rcm.259.