Mass Spectrometry Applications for Environmental Analysis

Importance of the Topic

Environmental contamination of water by pesticides and herbicides poses serious human health and ecological risks. Rapid, sensitive, and high-throughput methods are essential to monitor trace levels of these compounds in drinking, surface, and wastewater. Advances in mass spectrometry (MS), ionization technologies, and automated sample preparation enable faster response to contamination events and support routine quality control in environmental laboratories.

Objectives and Overview

This collection of studies presents innovative analytical workflows for detecting a broad range of agrochemicals at ng/L to pg/L levels. The goals include:

• Developing direct-analysis techniques combining ambient ionization (DART) with high-resolution Orbitrap MS for rapid screening of pesticides in water.
• Implementing on-line solid-phase extraction (SPE) systems (EQuan) coupled to triple quadrupole MS for large-volume sample preconcentration without offline cleanup.
• Optimizing chromatographic strategies—divert-valve HPLC, fast UHPLC, mixed-mode columns—to resolve early-eluting polar analytes and multiresidue panels.
• Automating data processing using targeted and non-targeted screening software (ExactFinder, TraceFinder) for reliable identification and quantitation.

Methodology and Instrumentation Used

Key platforms and approaches include:

• DART-SVP ambient ionization combined with Thermo Scientific Exactive Orbitrap MS (50,000 FWHM) for direct analysis of pesticides on metal meshes, achieving mass accuracy <1 ppm and detection of 23 targets at ng/mL levels.
• Thermo Scientific EQuan system with dual-pump LC and online SPE cartridges (Hypersil GOLD) for direct injection of up to 20 mL water, followed by backflush onto an analytical column (UHPLC or HPLC) and MS/MS detection on TSQ Quantum Access MAX.
• Divert-valve HPLC setup on an Accela UHPLC with Hypersil GOLD columns to overcome solvent effects for early-eluting pesticides, permitting injection volumes up to 8 µL in high-organic extracts.
• Chromeleon-controlled workflows for TraceFinder software to process targeted SRM data and perform non-targeted elemental composition searches.
• Mixed-mode Acclaim Trinity P1/Q1 columns enabling on-line SPE and UV detection for polar herbicides (paraquat, diquat) in compliance with EPA Method 549.2.

Main Results and Discussion

• DART-Orbitrap workflows provided rapid (<30 s per sample) full-scan high-resolution spectra, with reliable identification and isotopic confirmation of pesticides at sub-µg/L concentrations.
• On-line SPE-LC-MS/MS achieved detection limits down to 0.5–10 pg/mL for triazines and other herbicides, with linearity (R²>0.99) across three orders of magnitude and repeatability <15% RSD.
• Divert-valve strategies restored sharp peak shapes for polar actives in acetonitrile extracts and enabled larger loop injections without chromatographic distortion.
• Automated screening software accelerated data review, flagged out-of-range results, and facilitated discovery of non-target compounds in environmental samples.

Benefits and Practical Applications of the Methods

• Elimination of lengthy offline sample preparation and solvent exchanges reduces analysis time, labor, and contamination risk.
• High-resolution accurate mass (HRAM) and tandem MS provide confidence in compound confirmation and lower false positives.
• Online SPE allows direct processing of large water volumes, enhancing sensitivity for trace-level monitoring.
• Flexible chromatographic setups accommodate diverse polarity ranges, from ionic herbicides to hydrophobic pesticides.
• Integrated software workflows support both routine QA/QC and forensic or emergency response scenarios.

Future Trends and Possibilities

• Expansion of ambient ionization methods (e.g., DART, DESI) coupled with portable HRMS systems for on-site screening.
• Further miniaturization and multiplexing of online SPE cartridges to increase throughput and reduce solvent consumption.
• Integration of machine learning algorithms for non-targeted data mining, predictive retention modeling, and automated anomaly detection.
• Development of greener mobile phases and column chemistries to minimize toxic reagents while maintaining performance.
• Wider application of HRAM fingerprinting for emerging contaminants and speciation analysis in complex matrices.

Conclusion

Recent advances in ionization technologies, on-line sample preparation, UHPLC, and MS offer powerful tools for environmental analysis of pesticides and herbicides. The combination of DART-Orbitrap, on-line SPE-triple quadrupole, divert-valve UHPLC, and mixed-mode column strategies delivers high sensitivity, speed, and reliability for trace-level detection in water. Coupled with automated data processing, these workflows are well suited to meet stringent regulatory requirements and support proactive water quality monitoring.

Reference

• U.S. EPA Method 549.2: Determination of Paraquat and Diquat in Drinking Water.
• EU Directive 98/83/EC: Quality of Water Intended for Human Consumption.