Determination of Benzene and Toluene in Finished Motor and Aviation Gasoline with Agilent 6820 GC System Using ASTM Method D3606

Significance of the Topic

Gasoline remains one of the most widely used fuels for transportation. Monitoring toxic aromatic hydrocarbons such as benzene and toluene in finished motor and aviation gasoline is essential to ensure compliance with environmental regulations and to protect human health. A reliable analytical method provides rapid, accurate data for quality control, process optimization, and regulatory reporting.

Objectives and Study Overview

This study applies ASTM Method D3606 for quantifying benzene and toluene in refined gasoline, substituting a flame ionization detector for the standard thermal conductivity detector. Key goals include:

• Establishing a calibration protocol covering relevant concentration ranges
• Evaluating precision and repeatability against ASTM criteria
• Demonstrating effective separation of target analytes from complex sample matrices

Methodology

Samples are spiked with methyl ethyl ketone as an internal standard and introduced via manual injection. A nonpolar OV-101 precolumn removes heavy components by backflush, while lighter aromatics are directed onto a polar TCEP analytic column. Separation relies on differential boiling points and polarity. The six-port valve switches at a defined time to divert heavy fractions to waste and maintain column efficiency. Data acquisition and processing are performed with Cerity NDS software.

Instrumentation Used

• Agilent 6820 gas chromatograph with packed inlet
• Flame ionization detector maintained at 250 °C
• Six-port switching valve for backflush control
• OV-101 packed precolumn and TCEP packed analytic column
• Nitrogen as carrier gas, hydrogen and air for FID
• Cerity NDS software for system control and data analysis

Main Results and Discussion

Calibration for benzene and toluene proved linear over 0.06–5.0 % v/v and 0.50–20.0 % v/v respectively, with correlation coefficients exceeding 0.999. Chromatograms show clear resolution of benzene, toluene, and the internal standard from nonaromatic interferences. Repeatability tests across five replicate injections yielded relative differences within ASTM D3606 limits.

Practical Benefits and Applications

The described method delivers rapid, accurate quantification of aromatic content in gasoline streams. Its robustness and compliance with regulatory specifications support applications in refinery quality control, environmental monitoring, and fuel certification.

Future Trends and Opportunities

Advances in column technology and detector design may further improve throughput and sensitivity. Automation of sample preparation, integration with mass spectrometric detectors, and expansion to other volatile organic compounds represent promising developments for comprehensive fuel analysis.

Conclusion

The Agilent 6820 GC method using an FID and backflush valve meets or exceeds ASTM D3606 requirements for benzene and toluene determination in finished gasoline. The approach combines reliable separation, excellent repeatability, and straightforward maintenance, making it suitable for routine laboratory and industrial applications.

References

1. People’s Republic of China National Standard GB17930-1999
2. ASTM D3606-99 Standard Test Method for Determination of Benzene and Toluene in Finished Motor and Aviation Gasoline by Gas Chromatography