A High Performance and Cost‑Effective GC/MS Solution for Measuring Aromatics in Gasoline Using ASTM Method D5769

Significance of the Topic

Accurate quantification of benzene toluene and total aromatics in motor gasoline is essential for regulatory compliance environmental monitoring and quality control in the petroleum industry ASTM method D5769 is the primary standard approved by the US EPA for this measurement Use of a cost effective and high performance GC/MS platform can help laboratories transition from dye based methods and meet stringent calibration and performance requirements without excessive investment

Objectives and Study Overview

This study evaluated the Agilent 8860 GC coupled to a 5977 mass spectrometer modified with a stainless steel source to analyze benzene toluene and total aromatics in reformulated gasoline according to ASTM D5769 Key goals were to confirm calibration linearity performance requirements and compare results with an interlaboratory study program

Methodology and Instrumentation

The GC/MS system was configured to meet D5769 specifications

• GC inlet Split splitless at 350 to 1 helium carrier gas constant flow 1.8 mL per minute DB-1 column 60 m × 0.25 mm × 1 µm oven program from 60 °C to 250 °C
• MSD Electron ionization at 70 eV source temperature 230 °C quadrupole 150 °C scan range 45 to 300 amu at 3 scans per second
• Detector source modified by replacing the standard 3 mm draw-out plate with a 9 mm plate to extend linear range

Main Results and Discussion

Calibration linearity over a five point range was achieved for 27 aromatic analytes with coefficients of determination exceeding 0.999 following installation of the 9 mm plate Initial detector saturation for toluene at the highest calibration level was resolved by this simple modification Signal-to-noise for a low level test compound was 16.2 surpassing the D5769 requirement of five Chromatographic resolution between critical pairs exceeded the minimum of two Mass spectral ion ratio checks met all criteria Quality control standards were within ±5 percent of reference values for all compounds Ten replicate analyses of two reformulated gasoline samples yielded relative standard deviations below 2.1 percent for benzene toluene and total aromatics Z-scores against interlaboratory consensus fell within one standard deviation demonstrating excellent agreement

Benefits and Practical Applications

The modified 8860 5977 GC/MS platform offers

• Cost effective upgrade path for existing laboratories transitioning to D5769
• High precision and accuracy for regulatory reporting
• Extended detector linearity for high concentration analytes
• Compliance with performance and QC requirements of ASTM and EPA

Future Trends and Potential Applications

Further enhancements may include advanced source designs for even wider dynamic range integration with automated sample preparation high resolution MS detection and expansion to other complex hydrocarbon matrices Additional automation and data handling can streamline high throughput compliance testing

Conclusion

The Agilent 8860 GC coupled to the 5977 MS with a simple stainless steel source modification meets all D5769 performance criteria while delivering precise accurate and cost effective analysis of aromatics in gasoline Results compare favorably with interlaboratory consensus making this approach ideal for routine regulatory and quality control laboratories

References

1 ASTM D5769 Standard Test Method for Determination of Benzene Toluene and Total Aromatics in Finished Gasolines by Gas Chromatography Mass Spectrometry ASTM International West Conshohocken PA
2 40 CFR 80.46 Measurement of reformulated gasoline and conventional gasoline fuel parameters US Government Publishing Office
3 McCurry JD Improved Performance for the Analysis of Aromatics in Gasoline by ASTM Method D5769 Using the Agilent 5973 inert Gas Chromatography Mass Spectrometry System Agilent Technologies Application Note 5989-0093EN 2003
4 Agilent 5977 EI Source Selection Guide Agilent Technologies Publication 5991-2106EN 2013