Analysis of Aromatic Hydrocarbons in Gasoline and Naphtha with the Agilent 6820 Series Gas Chromatograph and a Single Polar Capillary Column

Importance of the Topic

The accurate quantification of aromatic hydrocarbons in gasoline and naphtha is essential for environmental compliance, fuel quality control, and public health. Regulatory limits on benzene and total aromatics drive the need for reliable analytical methods that can measure dozens of individual compounds in complex matrices.

Objectives and Study Overview

This study evaluates a streamlined gas chromatographic approach for the determination of 57 aromatic hydrocarbons in finished gasoline, blending feedstocks, and straight-run naphtha. The goal is to demonstrate that a single polar capillary column combined with internal standard calibration can deliver precise, reproducible results without complex valve systems or multiple columns.

Methodology

An internal standard method using n-tridecane was applied. Each sample was spiked to ~2 wt % IS and injected in split mode. Compounds were separated on a 60 m HP-INNOWax polyethylene glycol column with a temperature program from 40 °C to 240 °C. Quantitation used theoretical FID response factors based on molecular composition and a correction factor referenced to heptane.

Instrumentation Used

• Agilent 6820 Gas Chromatograph with split/splitless inlet
• Flame Ionization Detector (FID) at 240 °C
• HP-INNOWax capillary column (60 m × 0.25 mm, 0.25 µm film)
• Helium carrier gas at 1.4 mL/min

Key Results and Discussion

Chromatograms of reformate, heavy FCC gasoline, naphtha, and finished fuels showed baseline separation of over 50 aromatic targets and the internal standard. RSD values for most compounds were below 1 %, demonstrating excellent precision. Heavy feedstocks contained high-boiling aromatics such as biphenyl and dimethylnaphthalenes, while lighter fractions showed minimal nonaromatic interferences.

Benefits and Practical Applications

This single-column GC-FID method offers:

• Reduced instrument complexity—no valves or dual columns required
• Broad compound coverage—from benzene through C11 aromatics
• High precision—relative standard deviations typically <1 %
• Regulatory compliance—meets or exceeds ASTM, JIS, and Chinese standards
• Cost efficiency—faster throughput and simpler maintenance

Future Trends and Opportunities

Advances in stationary phases may further shorten analysis time and improve resolution. Coupling with mass spectrometry could enhance compound identification in complex blends. Automation and chemometric approaches will support real-time monitoring in refineries and blending centers. Emerging green solvents and detectors may reduce environmental impact.

Conclusion

The Agilent 6820 GC method with a single polar capillary column and n-tridecane internal standard provides a robust, reproducible, and streamlined solution for aromatic hydrocarbon analysis in gasoline and naphtha. It fulfills diverse regulatory requirements while simplifying routine laboratory workflows.

References

1. People’s Republic of China National Standard GB 17930-1999.
2. ASTM D5769: GC/MS determination of benzene, toluene, and total aromatics in finished gasoline.
3. ASTM D5580: GC method for benzene, toluene, ethylbenzene, xylenes, C9+ aromatics.
4. ASTM D3606: GC method for benzene and toluene in motor and aviation gasoline.
5. JIS K 2536-1996: Testing method for aromatic hydrocarbons using TCEP/PEG capillary column.