Hydrocarbons, C1 - C6 - Analysis of reference standard for impurities in 1,3-butadiene for ASTM method

Significance of the Topic

The accurate quantification of hydrocarbon impurities in high-purity 1,3-butadiene is critical for industries such as synthetic rubber production, pharmaceuticals and fine chemicals. Trace levels of C1–C6 contaminants can impact polymerization processes, catalyst performance and final product quality. A robust, fast and reliable GC method ensures consistent quality control and compliance with ASTM standards.

Study Objectives and Overview

This application note evaluates a microbore Agilent CP-Select 624 CB column for the separation and quantification of 25 hydrocarbon impurities (C1–C6) in a reference standard of 1,3-butadiene. The aim is to demonstrate improved resolution of reactive pentadienes and consistent response factors across a wide concentration range (20–2000 ppm).

Methodology and Instrumentation

A GC-FID method was developed using the following setup:

• Column: Agilent CP-Select 624 CB, 0.15 mm × 15 m WCOT, df = 0.9 µm
• Temperature Program: –20 °C hold 3 min → ramp 2 °C/min to 10 °C → hold 0 min → ramp 8 °C/min to 200 °C
• Carrier Gas: Helium at 110 kPa (1.1 bar)
• Injector: Split 1:100 via 4-port valve at 200 °C, sample volume 1 µL
• Detector: FID at 250 °C

These conditions enable fast throughput and sharp peak shapes even for reactive dienes.

Main Results and Discussion

The method achieved baseline resolution of 25 target analytes, including isomeric butenes and pentadienes. Representative impurity concentrations measured in the reference standard ranged from 5.6 ppm (trans-2-pentene) to 2073 ppm (trans-2-butene). Key observations:

• Excellent separation of cis- and trans-isomers of 2-butene and 1,3-pentadiene
• Stable response factors across different unsaturated hydrocarbons
• Rapid analysis cycle (< 20 min total run time)

Reactive sites on alumina are mitigated by the silicone-based CB phase, improving reproducibility for pentadienes.

Benefits and Practical Applications

This approach delivers:

• High sensitivity for trace-level impurities
• Robust performance on standard GC systems
• Compatibility with existing ASTM methods for industrial QA/QC
• Reduced analysis time due to microbore column efficiency

It supports routine monitoring in production, incoming feedstock testing and final product release.

Future Trends and Potential Applications

Advancements may include:

• Integration with mass spectrometric detectors for enhanced identification
• On-line process GC for real-time monitoring
• Development of novel stationary phases to further reduce reactive adsorption
• Automated data processing using machine learning for impurity profiling

Such innovations could further streamline hydrocarbon impurity analysis in continuous manufacturing environments.

Conclusion

The Agilent CP-Select 624 CB microbore column method offers a fast, reliable and high-resolution solution for quantifying C1–C6 impurities in 1,3-butadiene. Its robustness, sensitivity and compatibility with standard GC-FID systems make it a valuable tool for industrial quality control and regulatory compliance.

Reference

• L. d’Agostaro, H. Zhou, R. Cook, DCG Partnership, Pearland, Texas; Agilent Technologies Application Note A01544, October 2011