Detection of Sulfur Compounds in Light Petroleum Liquids According to ASTM D5623 with an Agilent Dual Plasma Sulfur Chemiluminescence Detector

Significance of the Topic

The precise detection and quantification of sulfur species in light petroleum liquids is critical for process control, equipment protection and environmental compliance. Sulfur compounds can be corrosive, foul catalysts and release odorous or toxic emissions. Implementing a robust analytical method aligns with ASTM D5623 requirements and supports refineries and laboratories in monitoring sulfur levels throughout fuel production.

Objectives and Study Overview

This application note evaluates the performance of an Agilent 7890B gas chromatograph coupled with an Agilent 8355 dual plasma sulfur chemiluminescence detector (SCD) to detect 23 volatile sulfur compounds, from ethanethiol to diphenyl sulfide, in petroleum fractions boiling below 230 °C. Key goals include demonstration of detector linearity, repeatability, limits of detection, stability over time and validation with NIST standard reference materials in accordance with ASTM D5623.

Methodology and Instrumentation

The analytical system comprised:

• Agilent 7890B GC with split/splitless inlet at 275 °C, split ratio 10:1 and DB-1 column (30 m×0.32 mm, 1 µm)
• Agilent 7650A automatic liquid sampler and 7696A Sample Prep WorkBench for calibration dilutions
• Agilent 8355 dual plasma SCD (burner 800 °C, H₂ flows 38/8 mL/min, O₂ 40 mL/min)
• Stock solutions prepared in isooctane at 0.1–100 ppm; internal standard diphenyl sulfide at ~30 ppm on-column

Calibration covered five concentration levels (0.01–10 ppm on-column) for 22 analytes in grouped mixtures, with a combined mix at 20 ppb (2 ppb on-column) to assess detection limits.

Main Results and Discussion

Linearity and repeatability were excellent: 95% of analytes achieved R² ≥ 0.999; RSD values ranged 0.6–9.5% at 0.1 ppm and improved at higher levels. Log–log calibration demonstrated consistent equimolar response across four representative compounds. A practical limit of detection of 2 ppb on-column was confirmed by resolving most peaks at a 20 ppb standard. Stability testing over two weeks (238 runs) yielded a mean relative response factor of 0.96 with 2.1% RSD, illustrating detector robustness. Analysis of NIST SRM 2299 and 2298 produced total sulfur values (12.5 µg/g and 3.5 µg/g) within certified tolerances.

Benefits and Practical Applications

The Agilent 8355 dual plasma SCD offers:

• Equimolar, hydrocarbon-immune response eliminating individual response factor determination
• Sub-ppb detection capabilities suitable for stringent regulatory methods
• High throughput with <14-minute total run time
• Excellent stability enabling extended sequence analysis with minimal recalibration

Applications include refinery streams, fuel quality testing, catalyst feed monitoring and routine QA/QC in petrochemical laboratories.

Future Trends and Applications

Advances in SCD technology may focus on integrating miniaturized GC systems for field analysis, coupling with automated sample preparation for high-throughput screening and expanding application scope to sulfur speciation in biofuels and environmental matrices. Combining SCD with multidimensional GC could further resolve complex sulfur profiles in advanced fuel blends.

Conclusion

The Agilent 7890B GC with 8355 dual plasma SCD delivers reliable, linear, equimolar detection of a broad range of volatile sulfur compounds compliant with ASTM D5623. It achieves detection limits down to 2 ppb, strong repeatability and extended stability, supporting critical petrochemical and environmental sulfur monitoring needs.

Reference

ASTM D5623: Standard Test Method for Sulfur Compounds in Light Petroleum Liquids by Gas Chromatography and Sulfur-Selective Detection