Analysis of Oil and Fat containing foods by fully automated sample preparation using a PAL3 coupled with a 7890 GC and a 5977 MSD system according to AOAC 996.01

Significance of the Topic

Pyrolysis gasoline is a key by-product of steam cracking used as an octane booster and industrial feedstock. Its complex composition, rich in BTEX and heavier aromatic compounds, poses analytical challenges such as extended elution times, column bleed, and sample carryover. Reliable analysis under ASTM D6563 is essential for quality control in petrochemical and fuel production.

Study Objectives and Overview

This application note evaluates the Agilent J&W DB-HeavyWAX GC column for pyrolysis gasoline analysis under ASTM D6563. The study compares this column’s performance to traditional WAX-type columns, focusing on thermal stability, reproducibility, carryover reduction, and overall analysis time.

Methodology

Pyrolysis gasoline samples were injected undiluted into an Agilent 7890B GC with FID detection and an Agilent 7693 autosampler. The DB-HeavyWAX column was operated to a final temperature of 280 °C, compared to 250 °C for traditional WAX columns. Carrier gas was helium at 1.2 mL/min, with split injection (200:1) at 250 °C. The oven program ramped from 70 °C (10 min) to final temperature at 5 °C/min.

Used Instrumentation

• Gas chromatograph: Agilent 7890B GC with FID
• Autosampler: Agilent 7693
• Columns:
  
  • Agilent J&W DB-HeavyWAX, 60 m × 0.25 mm, 0.25 µm
  • Agilent J&W DB-WAX (traditional), 60 m × 0.25 mm, 0.25 µm
• Carrier gas: Helium, constant flow 1.2 mL/min
• Inlet: Split mode, 250 °C, 200:1
• Detector: FID at 280 °C

Results and Discussion

The DB-HeavyWAX column demonstrated a significant reduction in column bleed at high temperature (8.2 pA at 280 °C) versus a traditional WAX column (18.2 pA at 250 °C). Higher molecular weight aromatics such as anthracene eluted cleanly without carryover when operating at the extended temperature limit. Selectivity for BTEX and C9+ aromatics remained comparable to standard WAX columns, facilitating method transfer with minimal adjustment.

Benefits and Practical Applications

Use of the DB-HeavyWAX column delivers:

• Reduced carryover and improved reproducibility across runs
• Shorter analysis times for high-boiling components
• Extended column lifetime due to controlled bleed
• Simplified method translation from existing WAX-based protocols

Future Trends and Opportunities

Ongoing developments may include tailored stationary phases for even higher thermal stability, coupling with mass spectrometric detection for enhanced compound identification, and integration of predictive maintenance algorithms for column health monitoring. High-throughput screening of heavy aromatics and alternative industrial streams represent emerging applications.

Conclusion

The Agilent J&W DB-HeavyWAX column offers superior thermal stability and reproducibility for ASTM D6563 analysis of pyrolysis gasoline. Its extended temperature capability enables reliable elution of heavier aromatics, reducing carryover and improving overall workflow efficiency.

Reference

1. Yang, D.; et al. Pyrolysis Gasoline Hydrogenation in the Second-Stage Reactor: Reaction Kinetics and Reactor Simulation; Industrial & Engineering Chemistry Research 2008, 47, 1051–1057.
2. ASTM D6563. Standard Test Method for Benzene, Toluene, Xylene (BTX) Concentrates Analysis by Gas Chromatography.
3. Abercrombie, V.; Provoost, L. Increased Thermal Stability and Maximum Temperature of the Agilent J&W DB-HeavyWAX Column. Agilent Technologies Application Note 5991-9035EN, 2018.