Detection of trace level herbicides from drinking water, surface water and ground water by automated online SPE-LC MS

Significance of the Topic

Ensuring safe water supplies requires accurate detection of herbicides at trace levels in drinking, surface and ground water. Automated online solid phase extraction coupled with liquid chromatography and triple quadrupole mass spectrometry enables sensitive, reproducible analysis with minimal manual sample preparation. This approach meets regulatory standards and supports environmental monitoring and public health initiatives.

Aims and Overview of the Study

This interlaboratory validation examined an automated online SPE–LC–MS/MS workflow for quantifying 27 neutral herbicides and metabolites in four water matrices. The study followed German DIN 38407-36 guidelines and assessed method linearity, accuracy, precision, recovery and throughput for spiked tap water, ground water and two surface waters at concentrations of 10 to 350 ng/L.

Methodology and Instrumentation

The method uses large volume injection (900 µL) and a dual trapping column configuration with parallel column regeneration. While one SPE column is loaded with sample, the other is cleaned and re-equilibrated. After valve switching, the trapped analytes are back-flushed onto the analytical column for separation. Key instrumentation and conditions included:

• Agilent 1260 Infinity Quaternary Pump with gradient of water and acetonitrile, both containing 5 mM ammonium formate and 0.1% formic acid, flow rate 0.4 mL/min at 30 °C
• Agilent 1260 Autosampler with 900 µL headspace and sample cooler
• Agilent 1290 Infinity Flexible Cube with a 2-position/10-port valve for solvent selection and column switching
• Agilent G6460A Triple Quadrupole MS with Agilent Jet Stream electrospray source operating in positive mode
• Data acquisition with dynamic multiple reaction monitoring in Agilent MassHunter software

Main Results and Discussion

Performance was evaluated in four spiked water samples. Key findings:

• Excellent linearity across 10–500 ng/L with correlation coefficients above 0.999
• Apparent recoveries generally within 80–120% of reference values, with occasional deviations for very polar or nonpolar herbicides
• Area precision RSD below 5% for most compounds; retention time RSD below 0.1%
• Consistent sensitivity and reproducibility across tap water, ground water and surface waters, including samples with higher matrix load

Benefits and Practical Applications

The automated online SPE–LC–MS/MS workflow delivers high sensitivity at trace levels with minimal manual intervention. Fast 22-minute runtime per sample supports high throughput laboratory operations. The method is well-suited for regulatory compliance testing, routine environmental monitoring and QA/QC in water utilities.

Future Trends and Potential Applications

Advances may include integration with on-line filtration and pre-concentration modules, expansion to cover broader classes of emerging contaminants, adoption of high-resolution mass spectrometry for non-target screening, and miniaturized flow-through systems for field-deployable monitoring.

Conclusion

The validated online SPE–LC–MS/MS system using dual trapping columns and Agilent instrumentation achieved reliable, high-precision quantitation of 27 herbicides in diverse water matrices. The approach meets regulatory accuracy and precision requirements while enabling rapid, automated sample analysis without time-consuming offline preparation.

Reference

• Detection of Trace-Level Herbicides in Drinking Surface and Ground Water Using the Agilent 1200 Infinity Series Online SPE Solution Application Note Agilent Publication Number 5991-2405EN
• DIN 38407-36 Draft German standard methods for the examination of water waste water and sludge HPLC-MS/MS F 36