SELECTIVE ANALYSIS OF TRACE LEVEL CARBONYL SULPHIDE IN PROPYLENE BY GAS CHROMATOGRAPHY AND CHEMILUMINESCENCE AS ALTERNATIVE DETECTION FOR ASTM D5303

Význam tématu

Trace level detection of carbonyl sulfide (COS) in propylene is critical for preventing catalyst poisoning and ensuring product quality in the petrochemical industry. Accurate quantification of COS at sub-ppm levels supports process control and compliance with product specifications.

Cíle a přehled studie / článku

This study explores a gas chromatographic method coupled with a sulfur chemiluminescence detector (SCD) as an alternative to the flame photometric detection specified in ASTM D5303. The goal is to achieve reliable detection of COS at concentrations below 30 ppb in a propylene matrix, overcoming challenges such as chromatographic co‐elution and hydrocarbon interference.

Použitá metodika

The analytical approach employs direct gas sampling via a 1 mL loop and injection into a capillary GC column (60 m × 0.53 mm ID, 4 µm methylsilicone). Helium serves as the carrier gas at 10 mL/min. Separation parameters are optimized to resolve COS from co‐eluting sulfur species and propylene.

Použitá instrumentace

• Gas chromatograph equipped with 60 m × 0.53 mm × 4 µm methylsilicone column
• Sulfur chemiluminescence detector (Sense SCD) using air and hydrogen reagents
• High‐purity helium carrier gas

Hlavní výsledky a diskuse

Response stability tests over 72 hours demonstrate ≤3 % RSD for key sulfur standards. The method achieves a limit of detection below 20–30 ppb for COS, with negligible quenching effects from the propylene matrix. Comparative data confirm the SCD’s superior sensitivity (≤0.3 pg S/s), wider linear range, equimolar response (≤10 % deviation), and high hydrocarbon selectivity (S/C ≥5 × 10^7) relative to PFPD and FPD+ detectors. A representative chromatogram resolves H₂S, MeSH, COS, DMS, and EtSH in a 100 ppb COS spike.

Přínosy a praktické využití metody

• High sensitivity and selectivity for trace COS in hydrocarbon matrices
• Robust, long‐term stability suitable for routine QA/QC operations
• Minimal matrix interference and single‐level calibration simplify workflows

Budoucí trendy a možnosti využití

Advances in chemiluminescence detector design—including rapid start‐up, automated diagnostics, and air‐based reagent systems—will further enhance throughput and reliability. Integration with multidimensional GC (GC×GC) and extension to other olefins and trace sulfur compounds are promising areas for future development.

Závěr

The Sense sulfur chemiluminescence detector provides a highly sensitive, selective, and stable solution for trace COS analysis in propylene, offering clear advantages over traditional PFPD/FPD methods and meeting the stringent requirements of industrial and regulatory applications.

Reference

Van Harmelen M. Selective analysis of trace level carbonyl sulfide in propylene by gas chromatography and chemiluminescence as alternative detection for ASTM D5303.