THE NEW STANDARD IN SPECIATING SULFUR AND NITROGEN BY GAS CHROMATOGRAPHY

Importance of the Topic

Modern petrochemical and environmental analyses demand highly sensitive and selective detectors for sulfur and nitrogen compounds. The SeNse Sulfur and Nitrogen Chemiluminescence Detectors address these needs by improving detection limits, equimolar response and dynamic range.

Objectives and Study Overview

This work presents the development and performance evaluation of the SeNse SCD/NCD, detailing its redesigned chemiluminescence principle for speciation of sulfur and nitrogen in hydrocarbon matrices. Key goals include sensitivity enhancement, stability improvement and compliance with ASTM D5504 standards.

Methodology

The detector oxidizes eluted components at 700–900°C in a furnace with air and hydrogen. Oxidized sulfur converts quantitatively to SO2, which is reduced and then reacts with ozone in the reaction cell, producing an excited SO2* species. Photon emission from this chemiluminescence reaction is filtered and measured by a photomultiplier tube. Calibration involved dynamic dilutions of standard gases to assess sensitivity, linearity and equimolarity.

Instrumentation Used

• Gas chromatograph with SeNse SCD/NCD furnace module
• On-board ozone generator
• Oil-free vacuum pump
• Photomultiplier tube (PMT) and optical filter
• Mass flow controllers for gas dilution

Main Results and Discussion

• Sensitivity: Detection limits below 5 ppb for H2S, COS, MeSH, EtSH and DMS (3σ criterion).
• Stability: RSD <2% over 2 hours and <3% over 24 hours.
• Linearity: Correlation coefficient >0.9999 for H2S from 5 ppb to 10 ppm.
• Equimolarity: Response factors within ±5% relative to H2S for common sulfur compounds.
• Selectivity: High suppression of matrix interferences, enabling trace quantification in natural gas, including odorants like tetrahydrothiophene at single-digit ppb levels.

Benefits and Practical Applications

The SeNse SCD/NCD offers:

• Enhanced sensitivity and dynamic range for trace-level sulfur and nitrogen analysis.
• Robust equimolar detection simplifying calibration across multiple species.
• Fast startup and stable performance ideal for routine QA/QC in refineries, petrochemical plants and gas distribution networks.
• Compliance with ASTM D5504 and similar standards for natural gas and gaseous fuel analysis.

Future Trends and Potential Applications

Advancements in detector miniaturization and digital flow control may further improve portability and automation. Integration with online monitoring platforms and machine-learning-based data analysis can enhance real-time process control and environmental monitoring. Potential expansion includes speciation of emerging biofuels and complex matrix analyses.

Conclusion

The redesigned SeNse Sulfur and Nitrogen Chemiluminescence Detector achieves superior stability, low detection limits and excellent equimolar response, surpassing existing ASTM requirements. Its performance and ease of use make it a new standard in GC-based speciation of sulfur and nitrogen in hydrocarbon matrices.

References

• ASTM D5504-12: Standard Test Method for Determination of Trace Sulfur Compounds in Natural Gas by Gas Chromatography.
• Marijn van Harmelen, PAC Chemical Analysis, SeNse SCD/NCD Application Note.