The Analysis of Trace Contaminants in High Purity Ethylene and Propylene Using GC/MS

Significance of Topic

Trace-level impurities in high-purity ethylene and propylene feedstocks can drastically influence polymerization yields, catalyst performance, and final product properties. Detecting contaminants at part-per-billion concentrations is essential for quality control, process optimization, and minimizing waste.

Objectives and Study Overview

This work evaluates Agilent Technologies/Wasson-ECE Application 460B-00, which integrates a 5973N GC/MSD system with multivalve, multicolumn chromatographic separation and Composite Analysis Control Software. The aim is to achieve sensitive, selective, and automated quantification of low-carbon impurities (oxygenates, mercaptans, sulfides, arsine, phosphine) in ethylene and propylene at ppb levels.

Methodology and Instrumentation

The analytical configuration uses a 6890 GC coupled to a 5973 MSD. A series of inert capillary columns and automated valve switching directs sample aliquots onto the optimal column for each analyte class. Composite methods sequence three targeted injections per sample, enabling separation of trace species from bulk monomer. Calibration standards were generated via permeation tubes, and performance was assessed by linearity, repeatability, and limits of detection (LOD).

Used Instrumentation

• Gas chromatograph: Agilent 6890 GC
• Mass spectrometer: Agilent 5973N MSD (later models compatible)
• Valve modules and sample loops (100 µL, 500 µL)
• Inert capillary columns (Wasson Part KZA, KZB)
• Control software: G1701 DA and Composite Analysis Control Software

Main Results and Discussion

Linearity across five to six calibration points yielded correlation coefficients of 0.992–1.000 for all analytes. Repeatability at low ppb levels showed relative standard deviations typically below 5%, with sulfur compounds between 1.95% and 9.31% RSD. Compared to GC/FID, MS detection improved sensitivity by ~50×; relative to GC/TCD, sensitivity gains approached ~5000×. SIM mode detection provided positive analyte identification, with LODs as low as 2 ppb for methyl mercaptan and 5 ppb for carbonyl sulfide.

Benefits and Practical Applications

Automated composite methods reduce hands-on time and deliver reliable, timely results (≈1 hour per assay). The enhanced sensitivity and selectivity of GC/MSD ensure accurate monitoring of monomer purity, supporting rapid feedback to production units. Integration into online sampling systems allows hourly assessments, minimizing off-spec product and improving overall process efficiency.

Future Trends and Applications

Expanding analyte scope to include additional oxygenates, aromatics, and other low-carbon species can further enhance feedstock characterization. Greater integration with process control, advanced data analytics, and real-time monitoring will drive smarter, more efficient polymer manufacturing. Developments in detector technology and software automation will continue to lower detection limits and operator intervention.

Conclusion

Application 460B-00 demonstrates robust performance for trace contaminant analysis in polymer-grade ethylene and propylene. Its combination of multicolumn separation, MS detection, and automated workflows delivers high sensitivity, specificity, and productivity for quality assurance in monomer processing.

References

1. Application 460B-00
2. Application 262-00