LC/Q-TOF Workflows for Comprehensive Micropollutant Analysis

Significance of the topic

Comprehensive detection and characterization of trace-level micropollutants in surface waters is critical for accurate exposure assessment and environmental risk management. Traditional targeted analyses may overlook unexpected or emerging contaminants, while high-resolution LC/Q-TOF workflows enable broader profiling of known, suspect, and unknown compounds.

Objectives and Study Overview

This study demonstrates three complementary LC/Q-TOF workflows for surface water analysis:

• Targeted quantification of 32 pesticide and herbicide standards.
• Suspect screening using accurate-mass libraries with and without MS/MS data.
• Identification of unknown transformation products (TPs) via in silico predictions and structure correlation.

Methodology

Surface water samples were processed by mixed-mode SPE, evaporated and reconstituted for LC/Q-TOF analysis. All Ions MS/MS acquisition in positive/negative ESI employed multiple collision energies (0, 10, 20, 40 V). Data were processed using MassHunter for targeted quantification and suspect screening. A custom PCD of plausible TPs based on EAWAG Pathway Prediction System output and CFM-ID fragmentation predictions supported unknown identification with MSC software.

Instrumentation

• Agilent 1260 Infinity Binary LC with ZORBAX Eclipse Plus C18 column (2.1×100 mm, 1.8 µm).
• Agilent 6530 Accurate-Mass Q-TOF with Jet Stream ESI source.
• Agilent MassHunter Qualitative and Quantitative Analysis software (v. B.07.00).

Main Results and Discussion

Targeted workflow detected 25 of 32 compounds in 51 river samples with method detection limits of 0.1–13 ng/L, recoveries of 70–110% and RSD ≤10% for most analytes. Suspect screening expanded the list to 85 candidates; 73 were confirmed via standards or MS/MS matching. Unknown ID revealed five new TPs not found by other approaches. Examples include confident identification of azoxystrobin, detailed isotope matching for fluridone, and elucidation of a dithiopyr TP structure (MSC score >92).

Benefits and Practical Applications

• Enhanced detection of known and unexpected micropollutants in environmental waters.
• Reduced dependence on analytical standards through library-driven suspect screening.
• Identification of transformation products supporting fate and risk studies.

Future Trends and Potential Applications

Advancements may include integration of GC/Q-TOF for volatile/nonpolar analytes, expansion of high-quality suspect libraries, improved in silico fragmentation algorithms, and automation of non-target screening workflows to facilitate routine environmental monitoring and regulatory compliance.

Conclusion

The combined targeted, suspect screening, and unknown identification workflows on LC/Q-TOF platforms deliver a comprehensive and high-confidence approach for micropollutant profiling in surface waters, surpassing traditional targeted methods and enabling discovery of novel transformation products.

References

• C. Moschet et al. Environ. Sci. Technol. 51(3), 1553–1561 (2017).
• C. Moschet et al. Anal. Chem. 85(21), 10312–10320 (2013).
• EAWAG-BBD Pathway Prediction System; http://eawagbbd.ethz.ch/predict/ (2016).
• F. Allen et al. Metabolomics 11(1), 98–110 (2015).