Use of the New 5973 inert for Determination of Low-Level Volatile Sulfur in Gaseous Streams

Importance of the Topic

Low-level volatile sulfur compounds can poison catalysts and degrade product quality in petrochemical and fuel industries. Growing regulatory limits and strict quality control demand sensitive, selective methods for sulfur detection at ppb levels, making optimized analytical approaches crucial for process safety and compliance.

Objectives and Article Overview

This application note assesses the Agilent 6890N/5973 Inert GC/MSD as an alternative to traditional sulfur-specific detectors (FPD, PFPD, SCD). It details system setup and optimization for quantifying and identifying eight volatile sulfur species at trace levels in various hydrocarbon matrices using scan and selected ion monitoring (SIM) modes.

Methodology and Instrumentation

All experiments used an Agilent 6890N GC coupled to a 5973 Inert MSD with a newly deactivated source and a 3 mm drawout lens. A 60 m × 0.32 mm × 5.0 µm DB-1 column was interfaced via a heated volatiles inlet and 6-port gas sampling valve. Calibration blends (5 ppm each sulfur compound) were prepared dynamically in helium, natural gas, propylene, or refinery gas using an Aux EPC module. Key parameters:

• Carrier gas: Helium at 1.9 mL/min, constant flow
• Injection: Split ratios from 1:1 to 50:1, inlet at 150 °C
• Column program: 40 °C (5 min) → 270 °C at 25 °C/min (2 min)
• MSD: Surface-deactivated source (230 °C), quadrupole at 150 °C, transfer line 280 °C, mass range 33–100 amu (scan); SIM dwell 100 ms per ion

Main Results and Discussion

Calibration in helium and natural gas showed excellent linearity (r² > 0.99) from tens of ppb to low ppm for all eight sulfur analytes. The inert source and 3 mm drawout lens eliminated adsorption and maintained symmetric peaks down to 16 ppb. SIM mode provided high sensitivity and selectivity, effectively overcoming hydrocarbon co-elution. For example, COS co-eluting with propylene showed only ~23% signal suppression, and quantitation remained linear from 20 ppb to 1.2 ppm.

Benefits and Practical Applications

The 5973 Inert GC/MSD delivers positive compound identification with low detection limits, minimal peak tailing, and resistance to quenching by co-eluting hydrocarbons. It is well suited for monitoring sulfur impurities in fuel feedstocks, basic petrochemicals, natural gas, and refinery gas to protect catalysts and ensure product quality.

Future Trends and Potential Applications

Further improvements in source inertness and detector sensitivity may extend GC/MSD capabilities to a broader range of polar and reactive trace analytes. Automated dynamic blending and advanced SIM programming will enhance throughput and robustness in environmental monitoring, petrochemical processing, and quality assurance.

Conclusion

The Agilent 6890N/5973 Inert GC/MSD provides a robust, sensitive, and selective solution for low-level volatile sulfur analysis in gaseous streams. Its enhanced inertness and optimized SIM methods enable reliable ppb-level quantitation even in challenging hydrocarbon matrices.

References

1. Firor R.L., Quimby B. A Comparison of Sulfur Selective Detectors for Low Level Analysis in Gaseous Streams. Agilent Technologies, Publication 5988-2426EN.
2. Firor R.L., Quimby B. Automated Dynamic Blending System for the Agilent 6890 Gas Chromatograph: Low Level Sulfur Detection. Agilent Technologies, Publication 5988-2465EN.
3. Firor R.L., Quimby B. Analysis of Trace Sulfur Compounds in Beverage Grade Carbon Dioxide. Agilent Technologies, Publication 5988-2464EN.
4. Firor R.L. Volatile Sulfur in Natural Gas, Refinery Gas, and Liquefied Petroleum Gas. Agilent Technologies, Publication 5988-2791EN.
5. Szelewski M., Wilson B., Perkins P. Improvements in the Agilent 6890/5973 System for Use with USEPA Method 8270. Agilent Technologies, Publication 5988-3072EN.
6. Prest H., Peterson D.W. New Approaches to the Development of GC/MS Selected Ion Monitoring Acquisition and Quantitation Methods. Agilent Technologies, Publication 5988-4188EN.