Analysis of Sulfur Compounds in Natural Gas by Nexis™ SCD-2030 According to ASTM D5504

Analysis of Sulfur Compounds in Natural Gas by Nexis SCD-2030 per ASTM D5504

Significance of the Topic

Sulfur‐containing species in natural gas streams pose critical challenges in the petrochemical sector. Corrosive effects on pipelines and equipment, catalyst deactivation in downstream processes, and regulatory mandates for low sulfur levels make accurate detection essential. A robust analytical approach ensures product quality, safety, and process control in gas production and refining.

Goals and Study Overview

This study demonstrates the quantification of fourteen trace sulfur compounds in natural gas using gas chromatography coupled with a sulfur chemiluminescence detector (SCD). Analysis follows ASTM D5504, focusing on method linearity, repeatability, and selectivity under real‐world sample matrices.

Methodology and Instrumentation

Sample Preparation:

• Three cylinder standards: (1) fourteen sulfur compounds in helium at 1 ppm(v/v), (2) high‐purity nitrogen, (3) natural gas blend with defined hydrocarbon composition.
• Dilutions to 50 ppb, 100 ppb, 500 ppb, and 1 ppm using a 200 mL gas syringe.

Chromatographic Conditions:

• Instrument: Nexis GC-2030 with an SCD-2030 detector.
• Injector: Split/splitless (SPI) at 150 °C, split ratio 1:9.
• Column: SH-Rtx-1, 60 m × 0.53 mm I.D., 7 µm film.
• Carrier gas: Helium at 6.0 mL/min, constant flow.
• Oven program: 30 °C hold 1.5 min, ramp 10 °C/min to 200 °C, hold 3 min.
• SCD settings: interface 200 °C, furnace 850 °C; H₂ 100 mL/min, N₂ 10 mL/min, O₂ 12 mL/min, O₃ 25 mL/min.
• All sample paths, valves, tubing treated with Sulfinert® to minimize adsorption.

Main Results and Discussion

Linearity and Repeatability:

• Calibration across 50 ppb–1 ppm yielded R² values ≥ 0.9994 for all analytes.
• Repeatability at 1 ppm (n=5) showed peak area RSDs below 2.31%.

Selectivity and Quenching Evaluation:

• Comparative chromatograms of sulfur standards in pure gas vs. natural gas matrix confirmed full detection of all fourteen compounds at 50 ppb.
• No significant baseline suppression or signal quenching by hydrocarbons was observed, demonstrating excellent SCD selectivity.

Benefits and Practical Applications

This GC-SCD method offers:

• High sensitivity for trace sulfur species, critical for regulatory compliance and process monitoring.
• Robust performance in complex gas matrices without extensive sample cleanup.
• Reliable repeatability and linear response to support quality control and R&D in refining, petrochemical, and natural gas industries.

Future Trends and Potential Applications

Emerging directions include:

• Integration of two‐dimensional GC and high-resolution detectors for comprehensive sulfur profiling.
• Automated on-line sampling and real‐time monitoring systems for continuous process control.
• Application of machine learning algorithms to chromatographic data for rapid pattern recognition and predictive maintenance.
• Miniaturized field deployable units for upstream gas field analysis.

Conclusion

Following ASTM D5504, the Nexis SCD-2030 system delivers precise, accurate, and selective analysis of multiple sulfur compounds in natural gas. Its strong linearity, low detection limits, and resistance to matrix effects make it a valuable tool for industrial analytics and quality assurance.

References

• ASTM D5504 – Standard Test Method for Sulfur Compounds in Natural Gas by Gas Chromatography.
• Shimadzu Application Note No. G306, First Edition March 2019.