Analysis of aromatics in gasoline by ASTM D5769 using gas chromatography–single quadrupole mass spectrometry

Importance of the Topic

Aromatic hydrocarbons like benzene and toluene impact gasoline's octane rating and environmental safety. Regulatory limits on benzene (≤1% v/v) and total aromatics (≤42% v/v) require accurate quantification to meet health and legal standards.

Objectives and Overview

This application note evaluates the Thermo Scientific ISQ 7610 single quadrupole GC-MS with XLXR detector for measuring monocyclic aromatics in gasoline according to ASTM D5769. The study aims to verify resolution, linearity, sensitivity, spectral accuracy, and sample accuracy under high analyte concentrations.

Methodology and Instrumentation

Gasoline samples and calibration standards containing deuterated internal standards were prepared in iso-octane. A six-point calibration (0.17–5.56% w/w; 1.4–17.7% for toluene) with internal standardization was used.

• GC system: Thermo Scientific TRACE 1610 with TRACEGOLD TG-1MS column (20 m×0.18 mm×0.40 µm)
• Autosampler: AI/AS 1610, injection 0.2 µL split 1:500 at 300 °C
• MS: Thermo Scientific ISQ 7610 single quadrupole with XLXR detector, EI mode (70 eV), full scan 45–300 m/z

Main Results and Discussion

Chromatographic separation of 25 target analytes was achieved in under 8 minutes, with resolution ≥3.23 for critical pairs. Calibration curves exhibited R2>0.99 across %vol ranges without detector saturation. Sensitivity for 0.01% w/w diethylbenzene yielded S/N≈48, exceeding the required S/N≥5. Ion ratio checks for key fragments met ASTM criteria. Accuracy tests with a QC standard and interlaboratory gasoline sample returned deviations <5% for most analytes, confirming method reliability. The NeverVent vacuum probe interlock enabled rapid source cleaning and column changes without breaking MS vacuum, enhancing uptime.

Benefits and Practical Applications

Rapid analysis (<9 min), wide dynamic range, and high sensitivity facilitate compliance monitoring and quality control in fuel production. Modular GC maintenance reduces downtime, promoting continuous operation in industrial laboratories.

Future Trends and Potential Applications

Advancements may include automated sample handling, two-dimensional GC-MS for complex mixtures, integration with machine-learning algorithms for data interpretation, and adaptation of XLXR detectors for other petrochemical analyses. High-throughput screening and online monitoring of fuel streams are promising extensions.

Conclusion

The ISQ 7610 GC-MS system with XLXR detector meets ASTM D5769 requirements for accurate, precise, and efficient quantification of gasoline aromatics at regulatory concentration levels. The approach delivers robust performance, minimal maintenance downtime, and reliable compliance data.

References

1. United States Environmental Protection Agency. 40 CFR Part 80 – Regulation of fuels and fuel additives.
2. European Environment Agency. Directive 98/70/EC on petrol and diesel fuel quality.
3. ASTM D5769-15, Standard Test Method for Determination of Benzene, Toluene, and Total Aromatics in Finished Gasolines by GC/MS, ASTM International.
4. Thermo Scientific Technical Note 000421: Extended linear dynamic range with the XLXR detector on the ISQ 7610 GC-MS.