Analysis of Sulfur Compounds Recommended by ASTM D5623

Significance of the Topic

The accurate analysis of sulfur compounds in light petroleum liquids is critical for environmental compliance, product quality control, and refinery process optimization. Trace-level detection ensures adherence to regulations such as ASTM D5623 and helps prevent corrosion, catalyst poisoning, and harmful emissions.

Objectives and Overview of the Study

This application note describes a gas chromatography method coupled with a sulfur chemiluminescence detector (GC-SCD) for the simultaneous determination of nineteen sulfur species at 10 ppm concentration levels in light petroleum fractions. The approach aims to achieve baseline separation, reliable quantification, and compliance with ASTM D5623 requirements.

Methodology and Instrumentation

A capillary GC separation was performed using a 30 m × 0.32 mm I.D., 4.0 µm SH-I-1MS column. The carrier gas was helium in constant column flow mode (2.8 mL/min). The oven program started at 40 °C (3 min hold), ramped at 10 °C/min to 250 °C, and held for 16 min. A split injection (1 µL, split ratio 1:9) at 275 °C was employed. The GC interface to the SCD was set at 200 °C, with the SCD furnace at 850 °C. Detector gases were H₂ (100 mL/min), N₂ (10 mL/min), O₂ (12 mL/min) and O₃ (25 mL/min).

Instrumentation Used

• Shimadzu Nexis GC-2030 with AOC-20i autosampler (SPL-2030)
• SH-I-1MS capillary column (30 m × 0.32 mm I.D., df = 4.0 µm)
• SCD-2030 sulfur chemiluminescence detector

Main Results and Discussion

The method achieved complete separation of all target analytes, including methyl and ethyl mercaptans, sulfides, disulfides, thiophenes, and benzothiophenes. Retention times showed good reproducibility, and the SCD provided sensitive, selective detection of sulfur species. Signal-to-noise ratios were sufficient to reliably quantify each compound at the 10 ppm level. The method demonstrated robustness over multiple injections with minimal baseline drift or peak tailing.

Benefits and Practical Applications of the Method

This GC-SCD procedure offers several advantages:

• High selectivity and sensitivity for a wide range of sulfur compounds
• Compliance with ASTM D5623 for light petroleum liquids
• Efficient analysis time via optimized temperature programming
• Automated sampling for improved throughput and reproducibility

Typical applications include refinery quality control, environmental monitoring, and process stream evaluation.

Future Trends and Applications

Advancements may include coupling with multidimensional GC for isomeric resolution, integration into online process analyzers for real-time monitoring, and further miniaturization of detectors. Emerging sulfur chemiluminescence technologies may offer enhanced sensitivity and reduced maintenance.

Conclusion

The described GC-SCD method on the Nexis GC-2030 platform provides a reliable, compliant, and efficient approach for quantifying trace sulfur compounds in light petroleum liquids. It meets industry standards and supports routine QA/QC in refining and petrochemical environments.

References

• Application News G305 (JP, ENG), Shimadzu Corporation, 2022