Analysis of PCBs and Organochlorinated Pesticides in River Water Using Simultaneous Scan/MRM Measurement in GC-MS/MS (2)

Significance of the Topic

Monitoring persistent organic pollutants such as PCBs and chlorinated pesticides in aquatic environments is essential for assessing ecological and human health risks. Ultra-trace analysis of these compounds informs water quality management and regulatory compliance.

Objectives and Study Overview

The study aims to evaluate simultaneous scan and multiple reaction monitoring (MRM) measurements using GC-MS/MS for accurate quantification of PCBs and chlorinated pesticides in river water. Sensitivity, repeatability, and selectivity are assessed, highlighting improvements over conventional SIM.

Methodology and Instrumentation

• Sample Collection and Pretreatment:
  • 1 L river water buffered with phosphate (1 mol/L, pH 7) and salted (50 g NaCl).
  • Liquid-liquid extraction twice with 50 mL dichloromethane; dehydrated with anhydrous Na₂SO₄.
  • Concentration to 1 mL via rotary evaporation and nitrogen blowdown; internal standard added.
• GC-MS/MS Conditions:
  • Simultaneous scan/MRM measurement as per Application Data Sheet No. 78.
  • Target analytes include mono- to hepta-chlorinated biphenyl congeners and chlorinated pesticides.
• Instrumentation Used:
  • Shimadzu GC-MS/MS system (model LAAN-J-MS-E079) configured for simultaneous scan/MRM.

Main Results and Discussion

• Chromatographic Performance:
  • Scan total ion chromatogram (TIC) revealed numerous matrix interferences.
  • MRM TIC eliminated most interferences via two-stage mass selection, enabling clean detection of target compounds.
• Comparison of MRM and SIM:
  • MRM chromatograms showed baseline separation and high sensitivity for PCB #52 and PCB #138/129 at ppt levels.
  • SIM mode suffered from coelution and overlapping impurities, reducing quantitative reliability.
• Quantitative Findings:
  • Detected 30 PCB congeners and chlorinated pesticides with concentrations ranging from 0.006 to 2.820 ng/L in river water.
  • Delta-BHC and hepta-chlorinated congeners were among the most abundant analytes.

Benefits and Practical Applications

Simultaneous scan/MRM on GC-MS/MS offers exceptional selectivity and sensitivity, enabling reliable quantification of trace organic pollutants at ppq–ppt levels. This approach supports routine environmental monitoring, regulatory compliance testing, and contaminant source tracing.

Future Trends and Potential Applications

• Integration of advanced data processing tools (e.g., compound databases and library matching) for non-target screening.
• Automation of sample preparation to improve throughput and reproducibility.
• Application to diverse environmental matrices such as sediments and biota.

Conclusion

The implementation of simultaneous scan/MRM measurements on a GC-MS/MS platform enables robust, high-throughput analysis of PCBs and chlorinated pesticides in river water. The enhanced selectivity and sensitivity facilitate accurate trace-level quantification, improving environmental risk assessments.