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

Importance of the topic

Multi-element isotope ratio analysis of nitrogen, carbon and sulfur has become an essential tool in areas such as food authenticity, environmental forensics and quality control. The ability to obtain three isotope signatures from a single small sample enhances throughput while reducing preparation time and cost.

Objectives and Overview of the Article

This application note describes modifications and performance of simultaneous N, C and S isotope ratio determination using a Thermo Scientific DELTA V isotope ratio mass spectrometer coupled to a Flash elemental analyzer and ConFlo IV interface. The goal is to demonstrate improved analysis speed and precision in a triple-element mode.

Methodology and Used Instrumentation

Key instrumental components and settings include:

• FlashEA 1112 elemental analyzer with a combined WO3/Cu reactor to combust sample and remove water via Mg(ClO4)2 trap.
• Thermo Scientific ConFlo IV interface for automated dilution and gas switching between up to five reference gases.
• DELTA V Plus IRMS with universal triple collector and fast/slow magnet field jumps for N2, CO2 and SO2 peaks.
• Sulfinert® capillaries and a 2 m PP-QS separation column to optimize chromatographic resolution and minimize background.

Main Results and Discussion

The optimized setup achieved baseline separation of N2 and CO2 within 17 s and clear SO2 elution, enabling a complete triple-element analysis in under 18 min. Precision (1σ) was ≤ 0.17‰ for d15N, ≤ 0.10‰ for d13C and ≤ 0.17‰ for d34S across diverse samples (amino acids, vitamins, soils, tissues). A C/S ratio below 70 ensured reproducible results.

Benefits and Practical Applications

Simultaneous triple-element analysis reduces sample throughput to three runs per hour, simplifies hardware modifications and lowers operational cost by using a single reactor and interface. This approach supports laboratories requiring high-volume screening for authenticity, ecological tracing and forensic investigations.

Future Trends and Possible Applications

Advancements may include faster chromatography via higher column temperatures, integration with automated sampling systems and expansion to additional isotopes. Coupling with miniature reactors or field-portable IRMS could extend applications into on-site screening.

Conclusion

This study illustrates a robust and efficient method for simultaneous N, C and S isotope ratio measurement on a DELTA V IRMS equipped with a Flash elemental analyzer. Minor modifications provide rapid, precise analysis across varied matrices, making it a versatile tool for multiple fields.

Reference

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