LC-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... 

Due to the potential value of this technique for the analysis of forensic samples that are of low volatility or are thermally labile, readers are referred to Mucdo and Jackson [11], Schmidt et al. [15], Thermo Electron Corporation [41], and Krummen et al. [38] for further discussions. Hettmann et al. [42] also discuss improvements to measurements using LC-IRMS. 

FIGURE 35.11 Schema representing a liqnid chromatography isotope ratio mass spectrometry (LC-IRMS) system. 

FIGURE 35.12 A chromatogram showing the separation of individual amino acids using mixed-mode chromatography coupled directly with an isotope ratio mass spectrometer via a liquid interface (LC-IRMS). 

Elflein, L. and Raezke, KP. (2008) Improved detection of honey adulteration by measuring drSerences between C-13/C-12 stable carbon isotope ratios of protein and sugar compounds with a combination of elemental analyzer-isotope ratio mass spectrometry and liquid chromatography—isotope ratio mass spectrometry (delta C-13-EA/LC-IRMs). Apidologie, 39 (5), 574-587. 

Because little has been said concerning difficulties arising from derivati-zation of samples to render them suitable for GC analysis, replacement of GC by HPLC for non-volatile or thermally labile compounds is a possibility. However, the demands of reproducible solvent removal for a reliable LC-C-IRMS approach are formidable. Caimi and Brenna [685,686] have developed an instrument based on a moving wire transport system. The analytes are deposited on the wire as they elute from the HPLC column and, after solvent drying at 200 °C, are transported into an 800 °C combustion furnace loaded with CuO, where the resulting C02 is picked up by an He carrier stream and swept via a drying trap into the IRMS. 

IRMS LC MDGC MS MSA NIF NMR OAV OSV PCA RAS RP SDE SFE SIM SNIF SPME TIC TLC Stable Isotope Ratio Mass Spectrometry Liquid Chromatography MultiDimensional Gas Chromatography Mass Spectrometry Multivariate Sensory Analysis Nasal Impact Frequency Nuclear Magnetic Resonance spectroscopy Odor Activity value Odor Spectrum Value Principal Component Analysis Retronasal Stimulation Reversed Phase Simultaneous steam Distillation Extraction Supercritical Fluid Extraction Selected Ion Monitoring Surface of Nasal Impact Frequency Solid Phase Micro Extraction Total Ion Current Thin Layer Chromatography... 

While the dual inlet technique is generally the most precise method for stable isotope ratio measurements, the continuous-flow technique offers online sample preparation, smaller sample size requirements, faster and simpler analyses, increased cost-effectiveness, and the possibility of interfacing with other preparation techniques, including elemental analysis, gas chromatography (GC), and liquid chromatography (LC). For these reasons, CF-IRMS is the subject of the majority of research currently being conducted in the field of forensic science [1],... 

Very recently, Bicchi et al. [2] compiled an overview on the use of deriva-tized cyclodextrins as chiral selectors for GC separation of enantiomers in essential oils and flavors. Analytical techniques such as capillary GC and GC-MS, two-dimensional GC, GC-IRMS, two-dimensional GC-IRMS, and liquid chromatography-capillary GC (LC-GC) were reviewed with respect to their applications to the enantiomeric separation. 

---