The Analysis of Monocyclic Aromatic Hydrocarbons by ASTM D7504 on the Agilent 8850 GC System

Importance of the topic

Monocyclic aromatic hydrocarbons (MAHs) such as benzene, toluene, ethylbenzene and the xylene isomers are critical building blocks in the petrochemical and chemical industries. Ensuring their purity is essential for quality control of fuels, solvents and feedstocks, as well as for process safety and regulatory compliance. ASTM D7504 is the established global standard for quantifying trace MAH impurities, but its conventional analysis can be time-consuming. Accelerating this method without compromising precision can greatly improve laboratory throughput and decision-making.

Objectives and study overview

This application study demonstrates two approaches for MAH analysis by ASTM D7504 using the Agilent 8850 GC system: a conventional separation with helium carrier gas and a 39-minute run time, and a fast separation with hydrogen carrier gas and a 6.05-minute run time. A secondary goal is to illustrate the use of Agilent’s method translator software to convert and optimize the conventional method into a high-speed protocol. Both approaches were evaluated in terms of separation performance, precision and detection limits.

Methodology

Two GC methods were developed on the Agilent 8850 GC equipped with split/splitless inlet, flame ionization detector and 7650A autosampler. The conventional method employed a 60 m × 0.32 mm, 0.5 µm HP-INNOWax column with helium carrier gas at 2.1 mL/min, split ratio of 100:1 and a 39-minute oven program. The fast method used a 20 m × 0.18 mm, 0.18 µm HP-INNOWax column with hydrogen at 1.5 mL/min, split ratio of 500:1 and a 6.05-minute ramped program. Precision studies of three commercial check standards (benzene, toluene, p-xylene) were performed with 20 consecutive injections each.

Instrumentation Used

• Agilent 8850 GC system with sixth-generation electronic pneumatic control
• Agilent 7650A autosampler (ALS)
• Split/splitless inlet and FID detector
• HP-INNOWax columns: 60 m × 0.32 mm, 0.5 µm (conventional); 20 m × 0.18 mm, 0.18 µm (fast)
• OpenLab CDS 2.7 for data acquisition and analysis

Results and discussion

The conventional method delivered baseline separation of all MAH peaks in ~23 min for each standard, with concentration %RSDs below 1.0% for non-trace analytes. The fast method achieved a ten-fold reduction in cycle time, completing separations in just over 6 min while maintaining sub-1% RSD precision. Benzene spiked at 14 ppmw in p-xylene gave an average RMS S/N of 60 (MDL ≈ 0.7 ppmw; MQL ≈ 2.3 ppmw) despite a 93% lower sample load. Retention time repeatability improved five-fold in the fast method thanks to the agile oven control and precise flow control.

Benefits and practical applications

• Sub-1% RSD precision for routine and trace MAH analysis
• High-speed protocol supports >6× throughput increase
• Lower carrier gas consumption and energy usage tracking via GC Intelligence
• Method translator tool simplifies method adaptation and optimization
• Compact footprint enables true instrument redundancy for critical QC labs

Future trends and opportunities

Laboratories will continue to leverage advanced GC features such as early maintenance feedback counters, remote monitoring of gas and power consumption, and integrated method-translation software. Further speed gains may be realized by exploring ultra-fast columns, alternative detectors or micro-GC configurations. The same principles can be extended to other standardized methods for VOCs and environmental analyses. Cloud-based data analytics and AI-driven diagnostics will further enhance uptime and method robustness.

Conclusion

The Agilent 8850 GC system demonstrates robust, precise performance for MAH analysis by ASTM D7504 in both conventional and high-speed formats. The fast method reduces runtime from 39 to 6.05 minutes without sacrificing precision or sensitivity. Agilent’s GC Intelligence features and method translator software streamline method development and maintenance, enabling higher throughput, lower running costs and improved laboratory efficiency.

References

1. ASTM D7504-23, Standard Test Method for Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas Chromatography and Effective Carbon Number, ASTM International, West Conshohocken, PA, 2023.
2. McCurry J. D., A Unified Gas Chromatographic Method for Aromatic Solvent Analysis, Agilent Technologies Application Note 5988-3741EN, August 2001.
3. Zhang Y., A Unified Method for the Analysis of Monocyclic Aromatic Solvents Using the Agilent 8860 GC System, Application Note 5994-1586EN, September 2022.
4. Pan J.; Wieder L.; McCurry J., Optimizing Productivity for Monocyclic Aromatic Hydrocarbon Purity Analysis on the Agilent 8890 GC, Application Note 5994-0597EN, January 2019.
5. Chemical Purity Analysis, Agilent Technologies Application Brief 5991-7220EN, September 2016.