Gas Chromatography – Isotope Ratio Mass Spectrometry
General Information
Unit
CNR-ISPTechnique
Key Instrumentation
Gas ChromatographyIsotope Ratio Mass Spectrometry (IRMS) is an analytical technique used to determine the relative abundances of stable isotopes of key elements (C, H, O, N, S) after quantitative combustion or pyrolysis of the sample, followed by gas-phase analysis. The mass spectrometer is coupled to two sample preparation modules, gas chromatography and elemental analysis, both equipped with combustion and pyrolytic furnaces to convert samples into simple gases. These gases are separated and analyzed by the mass analyzer to determine isotopic ratios. The elemental analyzer also enables the quantification of C, H, N, and S contents in unknown organic and inorganic compounds in solid and liquid non-volatile samples. All GC-EA-IRMS components are connected through the Thermo Scientific ConFlo IV Universal Interface. The Thermo Scientific GasBench II is an automated sample preparation system used for stable isotope ratio analysis (δ13C, δ18O, δD) of gaseous samples, including CO2 released from water, carbonates and dissolved inorganic carbon, water vapor, and headspace gases. The GC-MS system allows the quantification of non-polar volatile compounds in environmental matrices and is widely applied for the determination of persistent organic pollutants and pesticides in both urban and remote environments, including polar regions. It is also used to analyze personal care product-related compounds, such as fragrances, which have been detected not only in urban areas but also in Antarctica.
Technical description
Elemental Analyzer. The technique involves the introduction of small, precisely weighed aliquots of purified sample, which are combusted in excess oxygen to generate oxides. Quantitative combustion is ensured by an oxidation catalyst, followed by a reduction step to remove excess oxygen and convert oxides into molecular nitrogen, carbon dioxide, water, and sulfur dioxide. The resulting gases are separated by gas chromatography and analyzed using a thermal conductivity detector (TCD). Signals are processed with Eager Xperience software to determine the percentage of target elements.
Gas Chromatograph for CSIA. After chromatographic separation in the Thermo Scientific TRACE 1310 GC, compounds are converted to simple gases by combustion or pyrolysis in the GC-Combustion/Interface III. A backflush system removes solvents before the oxidation furnace, ensuring clean combustion and optimal GC performance. The produced gases are transferred in helium to the DELTA V Advantage IRMS via the Thermo Scientific ConFlo IV Universal Interface. This setup enables determination of D/H, 13C/12C, 15N/14N, and 18O/16O ratios for GC-resolved compounds, allowing compound-specific isotope analysis.
GasBench II and IRMS. The GasBench II system enables high-precision on-line isotope analysis of gaseous samples by headspace sampling, including water equilibration, carbonates, and atmospheric gases. Helium carrier gas allows GC separation and fractionation-free transport. All modules are connected throResearch areas and applications
Isotope Ratio Mass Spectrometry (IRMS), especially when coupled with Elemental Analyzers (EA), Gas Chromatography (GC), or Gas Bench (GB) systems, is a versatile analytical tool with wide applications across environmental, biological, and geological research. In Environmental and Earth Sciences, IRMS is used in paleoclimatology and climate change studies to analyze δ18O and δD in ice cores, waters, and carbonates for reconstructing past temperatures and hydrological cycles, and δ13C in atmospheric CO2 and tree rings to track greenhouse gas sources and sinks. In hydrology, δ18O and δD ratios are applied to trace the origin, mixing, and flow paths of surface and groundwater. In biogeochemical cycling, EA-IRMS measurements of δ15N and δ13C in soils, sediments, and biomass are used to investigate carbon and nitrogen cycling in ecosystems. Compound-specific isotope analysis (CSIA) by GC-IRMS (e.g., δ13C, δ15N) supports pollution source identification and degradation studies of organic contaminants such as pesticides and PAHs. In Biology and Ecology, stable isotope analyses of δ15N and δ13C in tissues are used to reconstruct trophic relationships, identify nutrient sources, and build food web models. In Archaeology and Anthropology, δ13C, δ15N, and δ18O measurements in bones and teeth provide insights into ancient diets, migration, and paleoenvironmental conditions. In Geology and Petrology, GC-IRMS supports oil–oil and oil–source rock correlations through compound-specific δ13C analysis, while isotopic compositions in minerals and rocks are used to constrain formation conditions and thermal histories.
Science highlights
D. Battistel, S. Viva, C. Turetta, S. Cadamuro, E. Bonato, F. Giummolè, N. Lonoce, C. Barbante, S. Gelichi, ArchaeolAnthropolSci, 16 (8), 117 (2024).
https://doi.org/10.1007/s12520-024-02032-2E. Argiriadis, M. Bortolini, N.M. Kehrwald, M. Roman, C. Turetta, S. Hanif, E.O. Erhenhi, J.M. Ramirez Aliaga, D.B. McWethy, A.E. Myrbo, A. Pauchard, C. Barbante, D. Battistel, PLoSONE, 16, e0254793 (2021). https://doi.org/10.1371/journal.pone.0254793
D. A. Kalashnikova, G. V. Simonova, O. V. Lyamkina, A. O. Pochufarov, JAnalChem, 78,
1055-1061 (2023). https://doi.org/10.1134/S1061934823070079
