Analysis of Environmental Contaminants in Surface Water and Wastewater Effluents Using GC/Q-TOF

Significance of the Topic

Environmental surface waters and wastewater effluents harbor a complex mixture of pesticides, industrial chemicals and emerging pollutants. Regulatory limits for many compounds are set at trace levels, demanding high sensitivity and selectivity. Broad‐scope and non‐targeted screening strategies are increasingly critical for comprehensive risk assessment of water quality.

Objectives and Study Overview

This work demonstrates a combined targeted, suspect and non‐targeted screening workflow using gas chromatography coupled to quadrupole time‐of‐flight mass spectrometry (GC/Q‐TOF) to profile over 1,000 pesticides and other environmental contaminants in surface water and wastewater effluents. The study aims to:

• Achieve simultaneous quantification and broad‐scope screening of trace compounds
• Correlate detected contaminants with observed toxicity in effluent samples
• Illustrate structure elucidation of unknowns by accurate mass MS/MS

Methodology and Used Instrumentation

Water and effluent samples were collected over multiple days, with whole‐effluent toxicity tests performed on Ceriodaphnia dubia. Samples underwent filtration (0.45 µm GF/F) and solid‐phase extraction on hydrophilic reversed‐phase cartridges. Eluates from ethyl acetate, methanol and hexane/acetone extracts were combined and spiked with internal standard before analysis.

• Chromatography: GC with backflush to reduce run time, improve retention stability and extend column life
• Detection: Agilent 7250 GC/Q-TOF equipped with high-resolution EI (70 eV and low-energy 12 eV), positive and negative chemical ionization (methane), and accurate mass MS/MS
• Data acquisition: Full-spectrum accurate mass at 2 spectra/s
• Data processing: MassHunter Quantitative Analysis, MassHunter Qual, Mass Profiler Professional, with accurate-mass libraries and NIST matching for unknowns

Main Results and Discussion

Over 90 compounds were identified by EI in each effluent sample. Negative CI extended coverage to polar pollutants. Suspect screening linked several pesticides (e.g. azoxystrobin, chlorantraniliprole) to acute toxicity observed at 80 % mortality. Non-targeted analysis and principal component analysis distinguished sample groups and pinpointed differential markers. Structure elucidation using accurate mass MS/MS identified unknowns such as acetyl triethyl citrate and a chlorothalonil degradation product (2,4,5-trichloroisophthalonitrile). Surface water profiling across four sites in the Sacramento-San Joaquin Delta revealed site-specific distributions of herbicides, insecticides and industrial by-products.

Benefits and Practical Applications

The GC/Q-TOF workflow offers:

• High mass accuracy and resolution for robust identification and confirmation
• Simultaneous targeted quantitation and broad-scope screening in complex matrices
• Retrospective data mining for newly emerging contaminants

Future Trends and Potential Applications

Advances may include expansion of accurate mass libraries, integration of AI‐driven deconvolution and suspect prioritization, miniaturized sampling and remote monitoring platforms, and coupling with orthogonal techniques (e.g. LC/Q-TOF) for even broader coverage of environmental pollutants.

Conclusion

This study highlights the versatility of high-resolution GC/Q-TOF for routine environmental monitoring. By combining targeted, suspect and non-targeted screening with accurate mass MS/MS, the method delivers comprehensive contaminant profiling, correlates chemical signatures with toxicity, and enables identification of unknown threat compounds.

References

• Application Note 5994-1345EN
• Application Note 5994-1371EN