Sulfur Chemiluminescence Detectors for Gas Chromatography

Importance of the Topic

Sulfur compounds in petroleum feeds and products can cause equipment corrosion, catalyst poisoning, and unpleasant odors. Accurate, sensitive, and selective analysis of these trace-level polar and reactive species is critical for quality control, environmental compliance, and process optimization.

Aims and Overview of the Study

This work evaluates the performance of Agilent’s dual plasma sulfur chemiluminescence detector (DP SCD) applied to two standardized methods: ASTM D5504 for natural gas and ASTM D5623 for liquid hydrocarbons. The goal is to demonstrate enhanced sensitivity, selectivity, and linear equimolar response for a range of sulfur species.

Methodology and Instrumentation

• Gas chromatograph: Agilent 7890 GC with splitless inlet and Sulfinert-treated capillary.
• Columns: HP-1 (60 m×0.53 mm×5 µm) for gas; HP-1 (30 m×0.32 mm×4 µm) for gasoline.
• Oven program: initial 30 °C hold, ramp to 200–250 °C at 10–15 °C/min, final hold of 1–3 min.
• DP SCD conditions: burner temperature 800 °C, burner vacuum 372 torr, reaction cell vacuum 5 torr, H2 at 40 ml/min, air at 53 ml/min.
• Injection modes: static and dynamic on-line gas blending for natural gas samples.

Major Results and Discussion

• Natural gas analysis identified 15 sulfur species with detection limits down to 1–2 ppb. Signal-to-noise ratios ranged from 1.0 to 12.0 at 1.35 ppb.
• Short-term (8 h) RSD values were typically below 3%, long-term (72 h) below 7% for most compounds.
• Gasoline samples (approx. 20 ppb total sulfur) showed repeatability RSDs of 0.9–8.6% (short-term) and 1.5–7.9% (long-term).
• On-line dilutor and dual plasma design minimized chemiluminescence quenching and maintained linear equimolar response.

Benefits and Practical Applications

• High selectivity over carbon background and minimal interference.
• Equimolar response allows direct quantitation without extensive calibration adjustments.
• Trace-level detection down to single-digit ppb supports environmental and process monitoring.
• Integration with FID provides parallel hydrocarbon profiling.

Future Trends and Opportunities

• Coupling DP SCD with GC×GC for enhanced resolution of complex matrices.
• Automated on-line sampling and dilution for remote or continuous monitoring.
• Miniaturized detectors for field-deployable sulfur analysis.
• Software advances for improved data processing and chemometric interpretation.

Conclusion

The dual plasma SCD on Agilent GC platforms offers a robust, sensitive, and selective solution for trace sulfur analysis in gaseous and liquid hydrocarbons, meeting and exceeding ASTM method requirements.

Reference

Wenmin Liu, Mario Morales, Thomas F. Daniels. “Sulfur Chemiluminescence Detectors for Gas Chromatography.” Agilent Technologies.