Isotope ratio mass spectrometry combustion interface

Authenticity evaluation has recently received increased attention in a number of industries. The complex mixtures involved often require very high resolution analyses and, in the case of determining the authenticity of natural products, very accurate determination of enantiomeric purity. Juchelka et al. have described a method for the authenticity determination of natural products which uses a combination of enantioselective multidimensional gas chromatography with isotope ratio mass spectrometry (28). In isotope ratio mass spectrometry, combustion analysis is combined with mass spectrometry, and the 13C/12C ratio of the analyte is measured versus a C02 reference standard. A special interface, employing the necessary oxidation and reduction reaction chambers and a water separator, was used employed. For standards of 5-nonanone, menthol and (R)-y-decalactone, they were able to determine the correct 12C/13C ratios, with relatively little sample preparation. The technical details of multidimensional GC-isotope ratio MS have been described fully by Nitz et al. (29). A MDGC-IRMS separation of a natural ds-3-hexen-l-ol fraction is... 

Isotope Ratio Mass Spectrometry (CCJ-IKMS). This was performed with a Finnigan MAT delta S isotope MS coupled on-line with a Varian 3400 GC via a combustion interface. Isotope ratios were expressed as 8-values [% ) versus the PDP... 

Stable isotope ratio mass spectrometers that interface directly to a gas chromatograph are commercially available. This type of analysis is known variously as gas chromatography-isotope ratio mass spectrometry (GC-IRMS), gas chromatography-combustion isotope ratio mass spectrometry, or compound-specific isotope analysis. The same principle of operation has also been used for more general isotope ratio analyses, where the components of interest are combusted as bulk samples. This type of arrangement, known as continuous flow-isotope ratio mass spectrometry, allows rapid automated analyses of and... 

FIGURE 15.7 Schematic showing a flash combustion EA in series with an interface and IRMS for the analysis of bulk nitrogen and carbon isotope values (based on a ThermoFinnigan Flash Elemental Analyzer [31]). Reprinted from Benson, S., Fennard, C, Maynard, R, Roux, C. (2006) Forensic applications of isotope ratio mass spectrometry—a review. Forensic Sci. Int., 157(1), 1-22, with permission from Elsevier [1]. 

Merritt DA, KH Freeman, MP Ricci, SA Studley, JM Hayes (1995) Performance and optimization of a combustion interface for isotope ratio monitoring gas chromatography/mass spectrometry. Anal Chem 67 2461-2473. 

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