Increasing Sensitivity for Tof-MS Detection of Polychlorinated Biphenyls (PCBs) Using Tof MRM

Importance of the Topic

Polychlorinated biphenyls (PCBs) are persistent organic pollutants linked to bioaccumulation, environmental persistence, and toxicity, including dioxin-like effects. Accurate detection at sub-ppb levels in complex matrices is critical for environmental monitoring, regulatory compliance, and risk assessment.

Objectives and Study Overview

This work introduces a time-of-flight multiple reaction monitoring (Tof MRM) acquisition mode on the Waters SYNAPT G2-Si platform. The goal is to enhance sensitivity for PCB congeners while concurrently acquiring high-resolution full scan data for comprehensive mass profiling.

Methodology and Instrumentation

• Instrumentation: Waters SYNAPT G2-Si quadrupole time-of-flight MS with T-Wave collision cell.
• Tof MRM Workflow:
  
  • Quadrupole selects PCB precursor ions.
  • Collision-induced dissociation (CID) generates product ions.
  • Timed TOF pushes synchronize with target product ions (35Cl and 37Cl isotopic variants) to enhance duty cycle.
• Full Scan Acquisition: Continuous recording from m/z 100 to 800.
• Calibration: Solvent standards of seven PCBs (28, 52, 101, 118, 138, 153, 180) prepared at 0.1–100 ng/mL.

Main Results and Discussion

• Excellent linearity over three orders of magnitude (R² > 0.995).
• High precision at 10 ng/mL (six replicates, %RSD < 10%).
• Sensitivity improvement: at least two-fold higher peak areas in Tof MRM versus conventional full scan TOF MS.
• Signal-to-noise ratios exceeding 7:1 at the 0.1 ng/mL detection level.
• Application to whale blubber extracts showed nearly doubled S/N for PCB 118 and enabled detection of additional congeners.
• Full scan data mining permitted identification of PBDEs with mass errors below 3 ppm, illustrating scope for unexpected contaminant screening.

Benefits and Practical Applications

• Lower detection limits without loss of accurate mass information.
• Simultaneous targeted quantitation and retrospective full scan screening.
• Robust performance in complex environmental and biological samples supports diverse monitoring and research needs.

Future Trends and Potential Applications

Emerging directions include expanded suspect and non-target screening libraries, advanced data processing algorithms, and extension of Tof MRM strategies to other classes of environmental contaminants and emerging toxicants.

Conclusion

Tof MRM on a high-resolution QTof platform delivers substantial sensitivity gains for PCB analysis while preserving comprehensive accurate mass data. This dual capability enhances both routine monitoring and exploratory contaminant discovery in complex matrices.

Used Instrumentation

• Waters SYNAPT G2-Si quadrupole time-of-flight mass spectrometer.
• T-Wave collision cell for collision-induced dissociation.

References

1. E. Reiner, R. Clement, A. Okey, C. Marvin. Analytical and Bioanalytical Chemistry, 386:791–806; 2006.