NIST SRM 1975, Diesel Particulate Extract, on Rxi®-PAH

Importance of the Topic

Polycyclic aromatic hydrocarbons (PAHs) in diesel particulate matter are recognized for their mutagenic and carcinogenic properties. Accurate determination of PAH levels supports regulatory compliance, environmental monitoring and health risk assessment in industrial and environmental laboratories.

Objectives and Study Overview

This application note describes a sensitive and selective gas chromatography–mass spectrometry (GC–MS) method using selected ion monitoring (SIM) for the analysis of 38 PAH compounds in NIST SRM 1975 diesel particulate extract. The goals were to achieve baseline separation, robust quantitation and reproducible retention times using an Rxi®-PAH capillary column.

Instrumentation Used

• Gas chromatograph: Agilent 7890B GC
• Mass spectrometer: Agilent 5977A MSD
• Column: Rxi®-PAH, 60 m × 0.25 mm ID, 0.10 µm film thickness
• Carrier gas: Helium, constant flow at 1.95 mL/min
• Injector: split 10:1, temperature 275 °C, 1 µL injection volume
• Ionization mode: Electron ionization (EI)
• Acquisition mode: Selected ion monitoring (SIM)

Methodology

The oven program begins at 110 °C (1.6 min hold), ramps at 24 °C/min to 210 °C, then at 1.9 °C/min to 295 °C, and finally at 3.7 °C/min to 350 °C (6 min hold). The mass spectrometer source is held at 350 °C, quadrupole at 200 °C, with DFTPP tune. Deuterated internal standards (D8-naphthalene, D10-acenaphthene, D10-phenanthrene, D12-chrysene, D12-benzo[a]pyrene, D12-perylene, D12-coronene) correct for matrix effects and signal drift. Target ions and dwell times are programmed across 24 SIM groups to ensure optimal sensitivity.

Main Results and Discussion

The method achieved clear resolution of all 38 target PAHs, with retention times ranging from 3.09 min (naphthalene-D8) to 64.78 min (indeno[1,2,3-cd]pyrene). Deuterated standards coeluted with native analogs, demonstrating consistent response factors. SIM transitions delivered low nanogram detection limits and high signal-to-noise ratios. Isomeric pairs, such as chrysene/benz[a]anthracene and benzo[b]fluoranthene/benzo[k]fluoranthene, were fully separated by the Rxi®-PAH phase.

Benefits and Practical Applications

• High sensitivity and selectivity for trace PAH quantitation in complex matrices.
• Robust reproducibility suitable for routine QA/QC and regulatory labs.
• Applicability to environmental monitoring, emissions testing and health-risk studies.

Future Trends and Opportunities

Advances in fast GC methods and high-resolution mass spectrometry could further reduce analysis time and enhance selectivity. Integration with automated sample preparation and online extraction can improve throughput. Emerging applications include ultra-trace monitoring of ultra-high molecular weight PAHs and coupling to multidimensional GC for enhanced isomer separation.

Conclusion

The described SIM-GC–MS method on an Rxi®-PAH column offers a reliable, sensitive and reproducible approach for comprehensive PAH profiling in diesel particulate extracts. Its robust performance supports diverse analytical needs from environmental compliance to toxicological assessment.

References

• NIST SRM 1975, Diesel Particulate Extract
• Restek Corporation Application Note GC_EV1392