Analysis of multiple matrices with a single calibration curve for polycyclic aromatic hydrocarbons (PAHs) with the ISQ 7610 GC-MS system following EPA Method 8270E

Significance of Topic

Polycyclic aromatic hydrocarbons (PAHs) are persistent environmental contaminants with carcinogenic and endocrine-disrupting properties. Monitoring PAH levels in soil and water is essential for assessing human and ecosystem health risks and ensuring compliance with environmental regulations such as EPA Method 8270E.

Objectives and Study Overview

This application study aimed to evaluate the Thermo Scientific ISQ 7610 single-quadrupole GC-MS system equipped with an XLXR detector and NeverVent technology for the simultaneous analysis of 19 EPA-listed PAHs in both soil and water matrices. A single calibration curve spanning five orders of magnitude was tested to streamline laboratory workflows and maintain compliance with EPA Method 8270E.

Methodology and Instrumentation

Sample Preparation and Calibration

• Solvent calibration standards prepared in dichloromethane ranging from 2.5 to 20,000 ng/mL, containing native PAHs, deuterated internal standards (1000 ng/mL), and surrogate standards (800 ng/mL).
• Instrument detection limits (IDLs) determined via eight replicate injections of a 2.5 ng/mL standard.
• Method detection limits (MDLs) calculated from extracted blank water and soil spiked at low levels, using EPA’s statistical approach.
• Quality controls (QCs) prepared at three levels (0.01, 1, and 10 ppm) in each matrix and injected randomly to assess method precision and accuracy.

Instrumentation

• GC-MS: Thermo Scientific TRACE 1610 GC coupled to ISQ 7610 single-quadrupole MS with ExtractaBrite ion source and XLXR detector.
• Autosampler: TriPlus RSH SMART.
• Column: TraceGOLD TG-PAH (30 m × 0.25 mm × 0.10 μm), enabling separation to 360 °C.
• Acquisition: Selected Ion Monitoring (SIM) for target PAHs and full-scan for source tuning (50–500 m/z).
• Software: Chromeleon 7.3 CDS with Environmental Analysis Pack for method control, data processing, SST, and reporting.

Main Results and Discussion

Chromatographic Performance

• Complete resolution of isobaric pairs (e.g., benzo[b]- and benzo[k]-fluoranthene resolution >20% valley height).
• Gaussian peak shapes achieved for all 19 PAHs, including high-boiling species, within a 15.2 min run.

Linearity and Dynamic Range

• Single calibration curve from 2.5 ng/mL to 20,000 ng/mL delivered average relative response factor RSDs <10% for all compounds.
• Extended dynamic range eliminated the need for separate curves for trace and high-level samples.

Sensitivity

• Instrument detection limits: 0.3–0.97 pg on column.
• Method detection limits: 0.44–6.94 pg on column (water), 0.48–7.60 pg on column (soil).

Precision and Accuracy

• Repeatability (n=10) at 20 ng/mL QCs: RSD <5.5% (water) and <15% (soil).
• QC recovery across 136 injections over 52 h: accuracy within ±20% (water) and ±15% (soil).

Robustness and Throughput

• No vacuum venting, source cleaning, column trimming, or MS retuning required during 52 h (136 injections) of continuous operation.
• Automated SST checks of DFTPP tune met EPA criteria throughout the batch.

Benefits and Practical Applications

• Single-curve calibration reduces preparation time and reagent use.
• XLXR detector’s extended linear range supports diverse contamination levels in one run.
• NeverVent capability minimizes unproductive downtime, maximizing throughput.
• High sensitivity and ruggedness streamline routine environmental monitoring by GC-MS.

Future Trends and Possibilities

• Integration with automated sample preparation and data management systems for higher laboratory efficiency.
• Expansion of method to include other semi-volatile organics and contaminants of emerging concern.
• Use of AI-driven data evaluation for rapid compliance reporting and pattern recognition in environmental datasets.

Conclusion

The Thermo Scientific ISQ 7610 GC-MS system with XLXR detector and NeverVent technology fully satisfies EPA Method 8270E requirements for PAH analysis in soil and water. Its wide dynamic range, low detection limits, robust operation, and streamlined workflow make it a powerful tool for high-throughput environmental laboratories.

References

1. Lammel G. Polycyclic Aromatic Compounds in the Atmosphere – A Review Identifying Research Needs. Polycyclic Aromatic Compounds 2015;35:316–329.
2. US EPA Method 8270E: Semivolatile Organic Compounds by GC-MS, Rev. 6, 2018.
3. Thermo Scientific AN10718: Fast Robust PAH Analysis in Drinking Water by Single-Quadrupole GC-MS, 2020.
4. US EPA Method 3510: Separatory Funnel LLE, 1996.
5. US EPA Method 3511: Organic Compounds in Water by ME, 2014.
6. US EPA Method 3546: Microwave Extraction, 2007.
7. Thermo Scientific TN10721: PAHs and PCBs in Soil by Single-Quadrupole GC-MS, 2020.
8. Thermo Scientific TN10499: Practical Determination of IDL in ISQ GC-MS, 2019.
9. US EPA Definition and Procedure for MDL, Rev. 2, 2016.