Robust analysis of PAHs and PCBs in soil with over 500 repeat injections using Orbitrap Exploris GC

Importance of the Topic

Persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) resist environmental degradation and bioaccumulate in soils and food chains. Sensitive, robust analytical methods are essential for routine trace‐level monitoring and regulatory compliance in complex environmental matrices.

Objectives and Study Overview

• Evaluate a simplified GC–Orbitrap method over 500 consecutive injections of soil extracts across three weeks
• Assess repeatability, relative response factor (RRF) stability, ion ratio precision, and mass accuracy
• Demonstrate suitability of the Orbitrap Exploris GC for routine environmental screening of PAHs and PCBs

Methodology and Used Instrumentation

• Sample Preparation: QuEChERS extraction of soil; extracts spiked at 10 pg/µL; low‐level QC standard (40 pg/µL) injected every 20 samples
• Chromatography: TraceGOLD TG-5 SilMS column (30 m × 0.25 mm × 0.25 µm); TriPlus RSH autosampler; Instant-Connect SSL injector
• Mass Spectrometry: Orbitrap Exploris GC with ExtractaBrite EI source and vacuum probe interlock; full‐scan acquisition (m/z 50–550); resolving power up to 60 000 at m/z 219
• Software: Chromeleon 7.3 with automated system suitability testing (SST) and intelligent run control (IRC)

Main Results and Discussion

• Peak Area Repeatability: RSD <20% (average ~10.5%) over 500 injections with only septa changes every 100 injections and no other maintenance
• RRF Stability: ≤15% RSD for all congeners (average ~4%); QC RRF deviations maintained within ±15% across 35 QC injections
• Ion Ratio Consistency: Qualifier/quantifier ion ratios stayed within ±15% of reference values (mean deviations ~2.4% for benzo[a]pyrene and ~0.7% for PCB 153)
• Mass Accuracy: Low (1‐indanone), mid (benzo[g,h,i]perylene), and high (PCB 180) m/z analytes showed ±1 ppm stability (avg. 0.3, 0.0, and 0.1 ppm respectively); overall QC average ~0.2 ppm over 35 injections

Benefits and Practical Applications

• Consolidated single‐run analysis of PAHs and PCBs enhances laboratory throughput
• Automated QC and intelligent run control reduce sample waste and minimize analyst intervention
• High instrument stability with minimal downtime lowers cost per sample
• Applicable for environmental monitoring, regulatory compliance, and QA/QC laboratories

Future Trends and Prospects

• Broader adoption of high‐resolution GC–MS for multi‐class and non‐target contaminant screening
• Advanced automation in sample preparation and data processing to further increase throughput
• Integration of real‐time monitoring and predictive maintenance to optimize uptime
• Development of standardized, high‐throughput workflows for environmental and industrial analytics

Conclusion

The Orbitrap Exploris GC system demonstrates exceptional robustness for routine trace analysis of PAHs and PCBs in soils, with excellent repeatability, stable response factors, consistent ion ratios, and sub‐ppm mass accuracy over a prolonged high‐throughput sequence. It fulfills the demanding requirements of environmental laboratories seeking reliable, consolidated GC–HRMS workflows.

Reference

• Guidance on information requirements and chemical safety assessment, part C: PBT/vPvB. ECHA, 2018.
• Thermo Fisher Scientific. Application Note 10731: Consolidated analysis of soil contaminants using Orbitrap Exploris GC, 2020.
• Thermo Fisher Scientific. Chromeleon 7.3: Built for the Lab. Built for IT. 2020.
• Thermo Fisher Scientific. Performing automated system suitability testing and intelligent run control, 2018.