Analysis of Benzene and Toluene by Brevis GC-2050 Using ASTM D3606

Importance of the Topic

Accurate quantification of benzene and toluene in fuels is critical for environmental safety and regulatory compliance. Due to the toxicity and carcinogenicity of these aromatic hydrocarbons, multiple national and international standards limit their concentrations in automotive fuels. ASTM D3606 provides established procedures for gas chromatographic determination, ensuring consistent results across laboratories and supporting fuel quality monitoring.

Objectives and Study Overview

This application note describes the use of the Brevis GC-2050 gas chromatograph to analyze benzene and toluene in spark-ignition fuels following ASTM D3606 Procedure A. The primary goals were to demonstrate:

• Linearity and accuracy of calibration curves over relevant concentration ranges.
• Sensitivity and signal-to-noise performance for trace-level benzene.
• Repeatability and reproducibility of quantitative results.
• Analysis time reduction through a capillary column backflush system.

Methodology and Instrumentation

Sample preparation involved dilution of fuel samples with isooctane and addition of methyl isobutyl ketone (MIBK) as an internal standard. Seven calibration mixtures (Mix 1–Mix 7) covered benzene concentrations from 0.06 to 5.0 Vol% and toluene from 0.5 to 20 Vol%. Chromatographic separation was achieved on a SH-Wax analytical column with a SH-1 pre-column and backflush timing set at 3.1 minutes to remove heavy matrix components. The split injection mode (0.5 µL) and helium carrier gas under pressure control ensured stable flow rates both before and during backflush. Two flame ionization detectors monitored the analytical column and restrictor tube to optimize backflush switching.

Used Instrumentation

• Brevis GC-2050 gas chromatograph
• AOC-30i/AOC-20i automatic injector
• SMI Flow Disc with 2-DET splitter for dual-FID configuration
• Pre-column: SH-1 (30 m × 0.25 mm I.D., 0.5 µm)
• Analytical column: SH-Wax (60 m × 0.32 mm I.D., 1 µm)
• FID detectors (two channels), detector temperature 200 °C

Main Results and Discussion

Calibration curves for both benzene and toluene exhibited excellent linearity with R² ≥ 0.999. The signal-to-noise ratio for benzene at low concentration (Mix 7) was 437, greatly exceeding the required S/N of 50. Resolution between benzene, toluene, MIBK, and other matrix peaks met or surpassed ASTM criteria (resolution values > 1.5). Repeatability tests (six injections of Mix 4) produced relative standard deviations below the specified limits (Δ ≤ 0.03 Vol% for benzene, Δ ≤ 0.10 Vol% for toluene). Reproducibility assessed with a certified JPI standard showed quantitation deviations within acceptable ranges (< 0.03 Vol% for benzene, < 0.78 Vol% for toluene). The backflush approach reduced total run time to under 15 minutes, improving laboratory throughput.

Benefits and Practical Applications

The Brevis GC-2050 system offers several advantages for routine fuel analysis:

• High sensitivity and accuracy for trace-level benzene detection.
• Backflush capability shortens analysis time and protects the analytical column.
• Compact footprint (≈ 35 cm width) enables installation in space-limited laboratories.
• Robust split-detector configuration provides reliable monitoring of the backflush process.

Future Trends and Opportunities

Advancements in capillary flow control and micro-detector technologies will further improve sensitivity and reduce analysis time. Integration of automated method optimization and real-time data processing could streamline routine monitoring. Miniaturization and portable GC systems may enable on-site fuel quality analysis, supporting mobile quality control in refining and distribution networks.

Conclusion

The Brevis GC-2050, combined with ASTM D3606 Procedure A and a backflush system, delivers precise, reproducible quantitation of benzene and toluene in spark-ignition fuels. Excellent linearity, sensitivity, and robustness make this configuration well suited for compliance testing and quality assurance in petrochemical laboratories.

References

• ASTM D3606-22 Standard Test Method for Determination of Benzene and Toluene in Spark Ignition Fuels by Gas Chromatography. ASTM International, West Conshohocken, PA, 2022.