Analysis of Trace Level Herbicides from Different Water Samples with the Agilent 1200 Infinity Series Online SPE Solution

Significance of the Topic

Effective monitoring of herbicide residues in water is critical to protect human health and aquatic ecosystems. Regulatory standards in the European Union restrict individual pesticide levels to 0.1 µg/L and the total pesticide sum to 0.5 µg/L in drinking water. Achieving reliable detection at low nanogram per liter levels without extensive sample preparation enhances laboratory throughput and cost efficiency.

Objectives and Study Overview

This study evaluated an automated online solid phase extraction method coupled with liquid chromatography and triple quadrupole mass spectrometry for the analysis of 25 herbicides and metabolites. The primary goals were to validate sensitivity down to 2 ng/L, assess precision and recovery in environmental water matrices, and demonstrate applicability to real ground, river, and stream water samples.

Methodology

An Agilent 1200 Infinity Series Online SPE system with dual trapping cartridges enriched 900 µL water samples directly without offline preparation. The SPE phase used PLRP-S cartridges, and sample cleanup was controlled by a binary pump and a 2-position/10-port valve in a Flexible Cube configuration. Chromatographic separation employed a ZORBAX Eclipse Plus C18 column with a water/ammonium formate/formic acid and acetonitrile gradient at 0.4 mL/min. Mass spectrometric detection used dynamic multiple reaction monitoring with optimized transitions for each analyte.

Instrumentation Used

• Agilent 1200 Infinity Online SPE Solution
• Agilent 1260 Infinity Binary Pump and Autosampler with 900 µL head
• Agilent 1290 Infinity Flexible Cube and Thermostatted Column Compartment
• Agilent 6460 Triple Quadrupole LC/MS with Jet Stream technology
• ZORBAX Eclipse Plus C18 analytical column and PLRP-S trapping cartridges
• MassHunter software suite for acquisition, optimization and quantitation

Key Results and Discussion

Calibration over 2 to 500 ng/L showed coefficients of determination above 0.997 for all compounds. Limits of detection around 2 ng/L and quantitation at 10 ng/L were achieved. Peak area precision in water samples was generally below 5% RSD, with retention time RSD under 0.1% over multiple cartridges. Carryover remained below 0.5% and was not quantifiable in environmental samples. All real water extracts contained herbicides well below the EU limit, with carbamazepine reaching up to 193 ng/L in some samples.

Benefits and Practical Applications

• Fully automated workflow eliminates manual cleanup steps
• High sensitivity at trace levels enables compliance monitoring
• Short analysis time and reuse of SPE cartridges enhance throughput and cost-effectiveness
• Robust performance in diverse water matrices ensures reliable data for regulatory and research purposes

Future Trends and Potential Applications

Integration of high-resolution mass spectrometry could broaden analyte scope and improve structural elucidation. Miniaturized online SPE modules and mobile LC/MS platforms may enable field-deployable water testing. Advances in data analysis using machine learning will streamline multiresidue quantitation and trend monitoring in environmental surveillance.

Conclusion

The described online SPE-LC-MS/MS approach delivers sensitive, precise, and efficient analysis of trace herbicides in water without offline pre-treatment. It meets stringent regulatory requirements and supports routine environmental monitoring with minimal hands-on time.

References

1. EU Council Directive on the Quality of Water Intended for Human Consumption, 98/83/EC, 1998
2. C Jansson and J Kreuger, Journal of AOAC International 93(6), 2010
3. B Schuhn, Agilent Technologies Application Note 5991-2405EN, 2013