Simultaneous N, C and S Isotope Ratio Determination on a DELTA V Isotope Ratio MS using a Flash Elemental Analyzer

Significance of the Topic

Multi-element isotope ratio analysis of nitrogen, carbon and sulfur provides critical insight in food authenticity, environmental forensics, and ecological studies. Combining three isotope systems in one run reduces sample usage and throughput time, advancing quality control and research workflows.

Study Objectives and Overview

This application note demonstrates a streamlined approach to simultaneous d15N, d13C and d34S measurement using a FlashEA 1112 elemental analyzer coupled to a DELTA V Plus isotope ratio mass spectrometer via a ConFlo IV interface and smartEA option. Key aims are to minimize analysis time, simplify sample handling and maintain high precision across diverse matrices.

Methodology and Instrumentation

A single reactor charged with WO3 and reduced copper wires combusts samples under an inert He flow. Water is trapped by magnesium perchlorate. Gas transfer employs Sulfinert® capillaries to prevent adsorption artifacts. A chromatographic column separating N2, CO2 and SO2 is held at 70 °C. The ConFlo IV interface manages five reference gases and performs automatic, software-controlled dilution (up to 1:100) in response to real-time TCD signals via the smartEA option. The IRMS, a DELTA V Plus with a triple collector, executes a rapid magnet jump between N2 and CO2 peaks and a slower jump to SO2.

Main Results and Discussion

Analysis of sulfanilamide (400 µg) achieved 17 s separation between N2 and CO2, enabling a fast magnet shift. Total run time per sample is under 18 minutes, allowing three samples per hour. Precision for pure compounds was better than 0.17‰ for d15N and d34S, and 0.10‰ for d13C. Heterogeneous or low-S samples (soil, sediments) saw minor precision decreases. Optimal sample S input is ≥30 µg and C/S ratio should remain below 70.

Benefits and Practical Applications

• High throughput: <18 min per sample enhances lab productivity.
• Minimal sample input: single drops of material reduce waste.
• Automated dilution and reference gas switching improve reproducibility.
• Applicability spans pharmaceuticals, environmental samples, biogenic materials and forensic analyses.

Future Trends and Possibilities

Expanding triple‐isotope analysis into routine QA/QC and field studies can drive new insights in biogeochemical cycles and provenance investigations. Ongoing improvements in column chemistries and miniaturized reactors may further shorten run times and lower detection limits, enabling in-line process monitoring in industrial environments.

Conclusion

Simultaneous determination of N, C and S isotope ratios on a DELTA V Plus IRMS with FlashEA and ConFlo IV smartEA achieves rapid, precise analysis across varied sample types. The approach requires minimal modifications to existing sulfur-capable EA setups and offers cost-effective, high-throughput performance.

References

• Avak H. Triple Element Mode – C, N, S from a single combustion. Application Flash Report No. 16, Finnigan MAT, 1996.