Wasson Chromatography Corner 10

Significance of the Topic

High-purity isobutylene and 1-butene are critical monomers and intermediates in petrochemical and polymer industries. Trace level impurities such as oxygenates, hydrocarbons, and sulfur compounds can poison catalysts, degrade product quality, and pose safety or environmental risks, making their accurate quantification essential.

Goals and Overview of the Article

This newsletter issue presents two analytical applications: quantification of hydrocarbons and oxygenates in high-purity isobutylene and 1-butene streams, and determination of total hydrogen sulfide in natural gas samples using headspace extraction and sulfur-specific detection. Additionally, it offers practical chromatography maintenance tips and training event announcements.

Methodology and Used Instrumentation

• Analysis of hydrocarbons and oxygenates in isobutylene/1-butene streams: An Agilent 7890A GC equipped with dual flame ionization detectors (FID/FID) was configured. A proprietary heart-cut trapping system isolated light components overlapping the main matrix peak. Captured analytes were desorbed thermally and re-injected onto a low-temperature secondary column before FID detection.
• Measurement of total hydrogen sulfide in natural gas: An Agilent GC fitted with a sulfur chemiluminescence detector (SCD) and an automated headspace sampler performed multiple headspace extractions (MHE) at 60 °C. Two methods based on ASTM D5504 and D6021 quantified H₂S and a range of volatile sulfur species down to sub-ppm levels.

Main Results and Discussion

• Oxygenates including acetaldehyde, isobutyraldehyde, various ethers, alcohols, and other volatile organics were detected by FID 1. FID 2 quantified C1–C8 paraffins and olefins (e.g., methane, ethylene, butadienes) with heart-cutting effectively resolving light compounds eluting within the isobutylene or 1-butene peaks.
• The SCD/HS method achieved a hydrogen sulfide detection limit of 0.015 ppmv. Multiple headspace extraction enabled quantification of heavier sulfur species alongside H₂S despite adsorption and reactivity challenges. System lines were Silcosteel®-treated and purged routinely to preserve sample integrity.

Benefits and Practical Applications

• Provides reliable ppm-level quantification of trace contaminants in monomer feedstocks to safeguard catalyst performance and product quality.
• Enables compliance with safety and environmental regulations by detecting corrosive sulfur species in natural gas.
• Turn-key, guaranteed solutions with installation, warranty, and service support tailored to industrial and research laboratories.

Future Trends and Opportunities

• Further refinement of trapping and heart-cutting strategies to lower detection limits and shorten analysis times.
• Expansion of headspace extraction protocols to broader classes of complex matrices and emerging contaminants.
• Implementation of remote monitoring and predictive maintenance tools to maximize instrument uptime and reproducibility.

Conclusion

Wasson-ECE’s specialized GC configurations—combining dual detectors, custom trapping, and multiple headspace extraction—demonstrate robust, sensitive methods for trace analysis of hydrocarbons, oxygenates, and sulfur compounds. These solutions support high-purity monomer production and natural gas quality assurance, delivering reliable data for process optimization and regulatory compliance.

Used Instrumentation

• Agilent 7890A Gas Chromatograph with dual FID detectors
• Proprietary low-temperature secondary column and thermal trapping system
• Agilent Gas Chromatograph with Sulfur Chemiluminescence Detector (SCD)
• Automated headspace sampler configured for multiple headspace extraction