Mass spectrometry GC-IRMS

Faulharber et al (5,6) and other researchers (7-9) have described how the determination of the isotope values of constituents is of increasing importance, especially in view of the demand for authenticity control and origin determination of essential oils and foods. To determine isotope values, g chromatography-isotope ratio mass spectrometry (GC-IRMS) has been used, although not widely. The present authors (70) have studied the possibility of a more convenient and common means of analysis of isotope values, based on the isotope peak in the mass spectrum of a compound. The present study focuses on the development of a new analytical method for the differentiation of quality in commercial citrus oils of various origins. 

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... 

Gas Chromatography Sano et al. first published a systematic approach to measuring the carbon isotope ratios of GC peaks in 1976 [34]. Further developments occurred over the years however, it was not until 1988 that gas chromatography-isotope ratio mass spectrometry (GC-IRMS) systems were commercially available. Since this time, the systems have been enhanced and extended to include the analysis of nitrogen, oxygen, and hydrogen isotope values [10 2]. Jasper et al. [35] describe the specificity of the GC-IRMS technique... 

Geochemical Applications of Gas Chromatography-Isotope-Ratio Mass Spectrometry (GC-IRMS)... 

Kahle K, Preston C, Richling E, Heckel F, Schreier P (2005) On-line gas chromatography combustion/pyrolysis isotope ratio mass spectrometry (HRGC-C/P-lRMS) of major volatiles from pear fruit (Pyrus communis) and pear products. Food Chem 91 449 Tamura H, Appel M, Richling E, Schreier P (2005) Authenticity assessment of y- and 5-deca-lactone from Prunus fruits by gas chromatography combustion/pyrolysis isotope ratio mass spectrometry (GC-C/P-IRMS). J Agric Food Chem 53 5397... 

Figure 10.4 Schematic representation of the multidimensional GC-IRMS system developed by Nitz et al. (27) PR1 and PR2, pressure regulators SV1-SV4, solenoid valves NV— and NV+, needle valves FID1-FID3, flame-ionization detectors. Reprinted from Journal of High Resolution Chromatography, 15, S. Nitz et al., Multidimensional gas chromatography-isotope ratio mass spectrometry, (MDGC-IRMS). Part A system description and technical requirements , pp. 387-391, 1992, with permission from Wiley-VCH.

The isotopic characterisation of organic compounds by classical elemental analysis with isotope ratio mass spectrometry (EA-IRMS) demands milligram amounts of pure compounds, which can not always easily be provided. Most analytes in flavour characterisation are volatile, and therefore, after their extraction, coupling of (capillary) gas chromatography (cGC) with IRMS would be an ideal tool for the isotope ratio analysis of the individual substances. For C- ]127, 128] and N-analysis ]179, 180] this has been realised for a long time by combining GC to IRMS via a combustion (C) unit (GC-C-IRMS), even for polar substances after their derivatisation ]181, 182]. 

D. SAMPLE PREPARATION FOR GAS CHROMATOGRAPHY-COMBUSTION-ISOTOPE RATIO MASS SPECTROMETRY (GC-C-IRMS)... 

GC-(high resolution)MS after enzymatic hydrolysis of the glucuro- and sulphoconjugates and trimethyl-silylation is the most widely used method for the determination of anabolic steroids and their metabolites in the urine of athletes. The most up-to-date technique for the solution of the difficult problem of differentiating between endogenous and exogenous testosterone is gas chromatography - combustion/ isotope ratio (C /C ) mass spectrometry (GC-C-IRMS). 

Liquid Chromatography While GC-IRMS instruments were commercialized in 1998, the interface allowing liquid chromatography-isotope ratio mass spectrometry (LC-IRMS) coupling was not commercially available until 2004 [38]. Godin et al. [39] provide a schematic overview of an LC instrument interfaced... 

FIGURE 35.10 Schema representing a gas chromatography isotope ratio mass spectrometry (GC-C-IRMS) system. 

The use of GC/combustion/isotope-ratio mass spectrometry (GC/C/ IRMS) has demonstrated distinguished capabilities to reveal misuse of endogenous steroids such as testosterone, dihydrotestosterone, dehy-droepiandrosterone (DHEA), etc. and was reported for the first time in 1994. The analysis of carbon isotope ratios of steroids in doping control specimens progressively improved, and in 1998 at the... 

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