Quantification of trace-level herbicides in drinking water by online enrichment with the Agilent 1200 Infinity Series Online-SPE Solution and Triple Quadrupole MS Detection

Significance of the Topic

This application explores the critical need for ultra-sensitive monitoring of neutral herbicides in drinking water to satisfy stringent EU Directive 98/83/EC limits. Achieving detection limits below 25 ng/L requires advanced sample enrichment and robust analytical performance to ensure water safety and regulatory compliance.

Objectives and Study Overview

The primary goal was to integrate an online solid-phase extraction (SPE) system with high-performance liquid chromatography and triple quadrupole mass spectrometry to quantify 28 trace-level herbicides at concentrations down to 0.5 ppt. Key performance metrics – linearity, precision, recovery, detection limits, and carryover – were evaluated, along with real-sample accuracy.

Methodology and Workflow

Water samples (river, tap, spring) were spiked, vortexed, filtered, and injected (1.8 mL) directly into an Agilent 1200 Infinity Series Online-SPE solution featuring dual trapping columns in alternating load/elute mode. Enriched analytes were backflushed onto a ZORBAX Eclipse Plus C18 analytical column under a water/acetonitrile gradient with formate/formic acid modifiers at 0.4 mL/min and 40 °C.
The Agilent 6460 Triple Quadrupole MS, equipped with Jet Stream ionization, monitored dynamic multiple reaction monitoring transitions. Optimized instrument parameters included gas and sheath flows, temperatures, and collision energies determined via MassHunter software.

Used Instrumentation

• Agilent 1200 Infinity Quaternary Pump with degasser
• Agilent 1260 Infinity Autosampler (1 800 µL multidraw)
• Agilent 1290 Infinity Flexible Cube with dual 2-position/10-port valves
• Agilent 6460 Triple Quadrupole LC/MS with Jet Stream
• ZORBAX Eclipse Plus C18 analytical column, PLRP-S SPE cartridges

Main Results and Discussion

Limits of quantitation ranged from 1 to 5 ng/L, with limits of detection as low as 0.5 ng/L. Calibration curves (1–100 ng/L) exhibited R² values above 0.995. Retention time precision was under 0.1% RSD and peak area RSD values typically fell between 5 and 8%. SPE recoveries exceeded 80% for most compounds, with 20 analytes above 90%. Carryover from a 100 ppt injection was below 0.3%, corresponding to less than 30% of the LOQ.
Analysis of spiked real-water samples delivered consistent results (precision RSD 2.3–2.8%, accuracy above 90%), demonstrating effective removal of matrix interferences and high method robustness.

Benefits and Practical Applications

Online enrichment allows large-volume injection without extensive off-line preparation, streamlining workflow and reducing manual handling. The approach meets and exceeds regulatory limits for multiple herbicides, enabling reliable routine screening in environmental and drinking water laboratories.

Future Trends and Potential Applications

Advances may include higher-throughput valve-switching schemes, novel sorbent materials for broader compound classes, and coupling with high-resolution or hybrid MS for non-target screening. Integration with automated data processing and predictive modeling will further enhance sensitivity, selectivity, and operational efficiency.

Conclusion

The combined Agilent 1200 Online-SPE and triple quadrupole MS platform delivers trace-level quantification of diverse herbicides with outstanding sensitivity, precision, and accuracy. This fully automated workflow satisfies stringent regulatory requirements and offers a powerful tool for environmental monitoring and water quality assurance.

References

1. European Union Drinking Water Directive 98/83/EC