Mass Spectrometry Applications for Environmental Analysis

Importance of Topic

Pesticide and herbicide residues in surface, drinking and waste waters pose serious risks to ecosystems and human health. Rapid, reliable and sensitive analytical methods are essential for monitoring regulatory compliance and responding to contamination events. Advances in mass spectrometry and on-line sample preparation now enable high-throughput screening and trace-level quantitation without lengthy off-line extraction.

Objectives and Study Overview

This collection of applications demonstrates the development of integrated workflows for environmental analysis of pesticides and related contaminants in water. Key goals include:

• Rapid screening of targeted and non-targeted compounds
• High-resolution, accurate-mass identification
• Elimination or automation of off-line sample pretreatment
• Sub-ppb to sub-ng/mL detection limits
• Enhanced throughput using direct analysis or on-line SPE coupled to LC-MS

Methodology and Instrumentation

Several analytical configurations were explored:

• DART-Orbitrap HRAM MS: Direct Analysis in Real Time ionization coupled to an Orbitrap Exactive platform for fast pesticide fingerprinting and accurate-mass confirmation.
• U-HPLC with Online SPE (EQuan) and Exactive MS: Large-volume water injections (1–20 mL) on a loading column, back-flush transfer and high-resolution MS detection.
• Fast-HPLC with TSQ Quantum Access: Rapid LC separation with a dual-pump system and divert valve for early-eluting analytes, coupled to triple quad MS for quantitative MRM.
• TraceFinder Software Workflows: Automated processing for targeted and non-targeted screening, calibration and reporting of triazine herbicides using TSQ QQQ data.
• Mixed-Mode Acclaim Trinity Columns with UV Detection: On-line SPE using Trinity P1 guard for paraquat/diquat, followed by separation on Trinity Q1 analytical column and UV quantitation.

Main Results and Discussion

• DART-Orbitrap enabled screening of 23 pesticides in water with mass accuracy < 1 ppm and detection down to 1 ng/mL in 30 s per sample.
• EQuan-Exactive workflow quantified 20 herbicides in drinking water at 20–600 ppt levels with excellent linearity (r² > 0.99) and ruggedness.
• Fast-HPLC MS/MS achieved elution of 11 pesticides in under 3 min and a total run time of 6 min, with injection volumes up to 8 µL and R² > 0.99.
• TraceFinder-guided TSQ MS analysis of triazines delivered sub-pg/mL detection with automated qualifier ion ratio checks and non-targeted identification of additional compounds.
• Divert-valve experiments improved peak shapes for early-eluters in acetonitrile extracts, enabling reliable quantitation of low–µg/L samples.
• On-line SPE with Acclaim Trinity P1/Q1 provided baseline separation and MDLs of 0.09–0.10 µg/L for paraquat and diquat, meeting EPA 549.2 and EU drinking water standards.

Benefits and Practical Applications

These integrated approaches offer:

• Substantial time savings by eliminating off-line SPE or solvent exchange
• High throughput for routine monitoring and emergency response
• Improved confidence through accurate mass and full-scan MS/MS confirmation
• Flexible injection volumes and streamlined method development with software-driven workflows

Future Trends and Potential Applications

Emerging directions include:

• Expanded non-targeted screening of transformation products and emerging contaminants
• Field-deployable or ambient-ionization MS platforms for on-site analysis
• Machine-learning algorithms for automated compound identification and trend monitoring
• Integration of multi-modal detectors (HRMS, UV, CAD) for orthogonal confirmation

Conclusion

The combination of innovative ionization techniques, high-resolution/quadrupole MS, on-line SPE and advanced software has transformed environmental water analysis. It now enables rapid, sensitive and robust screening and quantitation of pesticides and herbicides at trace levels, while significantly enhancing lab productivity and data confidence.

Instrumental Setup

• DART-SVP source and Exactive Orbitrap MS
• UltiMate 3000 x2 Dual RSLC with EQuan online SPE
• Accela UHPLC with TSQ Quantum Access MAX triple quad MS
• Acclaim Trinity P1 guard and Q1 analytical columns
• TraceFinder and LCQuan software for automated data processing

References

1. Cody RB, Laramee JA, Durst HD. Anal Chem. 2005;77:2297–2302.
2. Gross J. Mass Spectrometry. 2nd ed. 2011; Springer.
3. U.S. EPA Method 549.2: Determination of Diquat and Paraquat. 1997.
4. Rafferty JL, Siepmann IJ, Schure MR. J Chromatogr A. 2011;1218:2203–2213.
5. Beck JR, Yang C. Thermo Fisher Application Note 437; 2008.