Establishing Geochemical Standards and Methods for CHNS Abundances and CNS Isotopes

Significance of the Topic

Accurate measurement of carbon, hydrogen, nitrogen and sulfur abundances along with their stable isotope ratios is fundamental in geochemistry. These data underpin reconstructions of Earth’s geologic history, inform paleoenvironmental studies and enhance understanding of biological and geological processes over time.

Objectives and Study Overview

This work aimed to establish standardized methods and reference materials for combined CHNS abundance and isotope ratio analysis using a single analytical system. By evaluating rock samples of varying ages and maturities, including USGS and IAEA standards, the study assessed accuracy, precision and reproducibility.

Methodology and Instrumentation

• Flash combustion within an elemental analyzer enabled dynamic sample oxidation.
• Gases produced were separated by gas chromatography and quantified for abundance with a thermal conductivity detector.
• For isotope analysis, separated gases were introduced to an isotope ratio mass spectrometer.
• Automation and throughput were enhanced by a multiport autosampler and integrated software data handling.

Used Instrumentation

• Thermo Scientific Flash IRMS Elemental Analyzer for combined abundance and isotope measurements
• MAS Plus Autosampler for sample introduction
• Gas chromatograph with Thermal Conductivity Detector for CHNS quantification
• Thermo Scientific MAT253 IRMS for isotope ratio determination

Main Results and Discussion

• Calibration with BBOT and international isotope standards (USGS-41, USGS-40, IAEA-S2, IAEA-S3) yielded linear response (r²≈1.00).
• Rock samples analyzed in replicates showed low relative standard deviations (<1%) for elemental abundances and isotope values.
• Comparison with independent EA and IRMS setups demonstrated excellent agreement in both abundance and isotopic data.

Benefits and Practical Applications

The integrated system reduces analysis time and cost by eliminating separate instrumentation for elemental and isotopic measurements. High throughput, automation and robust data quality support applications in geologic research, environmental monitoring and quality control in industrial laboratories.

Future Trends and Potential Uses

• Expansion of standardized reference materials covering broader matrices and trace-level concentrations.
• Integration with high-resolution separation techniques for compound-specific isotope analysis.
• Development of workflows for in situ microanalysis and field-deployable systems.

Conclusion

The single-platform EA-IRMS approach provides accurate, precise and reproducible CHNS abundances and stable isotope ratios. It streamlines geochemical workflows and sets a new benchmark for analytical standardization in earth and environmental sciences.

Reference

Establishing Geochemical Standards and Methods for CHNS Abundances and CNS Isotopes. Liliana Krotz, Michael Stalker, Francesco Leone, Guido Giazzi, Eva Stüeken. Thermo Fisher Scientific; CE Elantech; University of St. Andrews. Presented at PittCon 2019.