Automated liquid-liquid extraction workflow for direct ultra-trace analysis of pesticides and PAHs in water matrices using GC-MS/MS

Importance of the Topic

The protection and monitoring of surface and drinking water are critical for human and environmental health under strict EU regulations such as the Water Framework Directive and the Drinking Water Directive.
High sensitivity and accuracy at parts-per-trillion levels are required for semi-volatile organic pollutants like polycyclic aromatic hydrocarbons and pesticides.

Objectives and Study Overview

This application note demonstrates an automated liquid liquid extraction workflow using the Thermo Scientific TriPlus RSH SMART autosampler combined with large volume injection GC tandem mass spectrometry for ultra-trace analysis of 78 target compounds in water matrices.
The study evaluates sensitivity, precision, robustness, and compliance with EU Directive 2020/2184 while improving laboratory productivity.

Methodology and Instrumentation

Sample preparation was performed on 20 mL vials with automated addition of internal standards, pentane extraction solvent, vortex mixing, isopropanol for emulsion removal, and automated phase transfer.
A 30 μL aliquot of the extract was injected in splitless mode via a programmable temperature vaporization inlet into a Thermo TRACE 1610 GC equipped with a TraceGOLD TG5 SilMS capillary column and a 5 m guard retention gap.
Detection was carried out on a Thermo TSQ 9610 triple quadrupole mass spectrometer with an Advanced Electron Ionization source in selected reaction monitoring mode.
Workflow control and data processing were integrated in Chromeleon CDS using the Sampling Workflow Editor.

Key Results and Discussion

Calibration curves for all 78 analytes were linear with coefficients of determination above 0.99 over 2 to 150 ng/L.
Limits of quantification were below 2 ng/L for more than 70 percent of compounds.
Extraction recoveries in spiked drinking water (10 ng/L) met the 70–130 percent criterion, while surface water showed matrix-related degradation for a subset of pesticides, rescued by isotopic standards.
Method precision over 80 injections remained within ±40 percent for PAHs and ±30 percent for most pesticides.
Automated extraction reduced solvent consumption from 16 L to 120 mL for 80 samples and enabled unattended 65 hour operation.

Benefits and Practical Applications

The automated workflow delivers high throughput and consistent analytical performance while minimizing solvent use and manual errors.
This approach supports regulatory compliance for ultra-trace water analysis and enhances laboratory safety and efficiency.

Future Trends and Applications

Future developments may include expansion to additional compound classes and matrices, customization of automated sequences, integration with real time data analytics, and adoption of greener extraction solvents.
Continued advances in automation will further improve trace analysis capabilities and environmental monitoring.

Conclusion

The TriPlus RSH SMART automated liquid liquid extraction combined with GC MS/MS provides robust, sensitive, and high throughput analysis of PAHs and pesticides at ultra trace levels in water, fulfilling stringent EU requirements and reducing laboratory costs and environmental impact.

References

1. Directive 2000/60/EC establishing a framework for Community action in the field of water policy
2. Directive 98/83/EC on the quality of water intended for human consumption
3. Directive (EU) 2020/2184 on the quality of water intended for human consumption (recast)
4. Thermo Fisher Scientific Case Study 001327 on the TriPlus RSH autosampler implementation
5. Thermo Fisher Scientific Automated Workflow Solutions for GC and GC MS