GC-MS/MS determination of PCBs and screening of environmental pollutants using simultaneous scan and MRM modes

Significance of the Topic

The persistent nature and toxicity of polychlorinated biphenyls and organochlorine pesticides pose serious risks to environmental and human health. Rapid and comprehensive detection methods are crucial for monitoring water quality and ensuring regulatory compliance. Integrating targeted quantitation with broad-spectrum screening in a single analytical run enhances efficiency in environmental analysis.

Objectives and Study Overview

This study aimed to develop and validate a gas chromatography tandem mass spectrometry (GC-MS/MS) method capable of simultaneously quantifying PCBs and organochlorine pesticides with multiple reaction monitoring (MRM) and screening a wide range of environmental pollutants using scan mode. The approach sought to reduce analysis time while maintaining high sensitivity and specificity.

Methodology and Sample Preparation

• Sample Collection: One liter of river water from Vietnam.
• Extraction: Liquid-liquid extraction with dichloromethane (2×50 mL) after salt addition and phosphate buffering.
• Concentration: Rotary evaporation to 5 mL, solvent exchange to hexane, and final concentration under nitrogen to 1 mL.
• Internal Standards: Five deuterated PAHs at 10 µg/mL spiked prior to analysis.
• MRM Quantitation: Isotope dilution for precise measurement of 30 PCB congeners and 22 organochlorine pesticides.
• Scan Mode Screening: Automated Identification and Quantification System with Database (AIQS-DB) for semi-quantitation of 942 registered pollutants.

Instrumentation Used

• Gas Chromatograph: Shimadzu GCMS-TQ8030 with DB-5MS capillary column (30 m × 0.25 mm, 0.25 µm).
• Injection: Splitless at 250°C, linear velocity control at 40 cm/s, 1 µL injection volume.
• Oven Program: 40°C (2 min), ramp 8°C/min to 310°C, hold 5 min.
• Mass Spectrometer: Triple quadrupole, interface 200°C, ion source 300°C, scan/MRM acquisition at 5000 u/sec.

Key Results and Discussion

The method achieved sensitive detection limits for PCB congeners down to sub-picogram per liter levels. In the Vietnamese river water sample, 30 targeted analytes were quantified, including mono- to decachlorobiphenyls and major organochlorine pesticide residues such as hexachlorobenzene and DDE. MRM transitions provided high selectivity, while scan data combined with AIQS-DB enabled the semi-quantitative identification of 84 additional pollutants across diverse chemical classes. Simultaneous acquisition reduced total run time and sample handling.

Benefits and Practical Applications

• Single-run analysis reduces laboratory workload and solvent use.
• High specificity MRM ensures accurate quantitation of priority pollutants.
• Comprehensive screening supports non-targeted environmental monitoring without individual standards.
• Applicable to regulatory compliance, water quality assessment, and contamination source tracking.

Future Trends and Applications

Advances in database expansion and machine learning algorithms may further automate pollutant identification. Integration with high-resolution MS and alternative ionization techniques will broaden compound coverage. Real-time field-deployable GC-MS/MS systems could enable on-site screening, accelerating environmental decision-making and risk assessment.

Conclusion

The developed simultaneous scan/MRM GC-MS/MS method offers a robust platform for targeted quantitation of PCBs and organochlorine pesticides alongside broad-scale screening of environmental contaminants. This dual-mode approach enhances analytical throughput and provides comprehensive data to support environmental monitoring and protection efforts.
If references: omitted due to none provided.