Fully automated solution for the extraction of Non-Polar Pesticides by GC

Importance of the Topic

Non-polar pesticides pose significant environmental and health challenges due to their persistence, low water solubility, and tendency to bioaccumulate in aquatic organisms. Monitoring trace concentrations of these compounds in surface and drinking water is critical for ensuring regulatory compliance and safeguarding ecosystems and human health.

Objectives and Study Overview

This technical note describes the development and validation of a fully automated liquid-liquid extraction method for 55 non-polar pesticides at sub-µg/L levels. Building on an earlier off-line protocol, the authors optimized a workflow using a Dual-Head Gerstel MPS 2 with mVorx agitation and Agilent GC-MS/MS detection to streamline sample preparation, improve reproducibility, and maintain sensitivity down to 10 ng/L.

Methodology and Used Instrumentation

Sample preparation was performed directly on 8 mL aqueous standards spiked at six concentration levels (10–150 ng/L) with internal standards. After addition of ethyl acetate and hexane, vigorous mixing via the mVorx module facilitated phase separation. A 20 µL aliquot of the upper hexane layer was injected into an Agilent 7890 GC equipped with a 7000C triple quadrupole MS using MSI multireaction monitoring (MRM) for each pesticide. Key instrument components included:

• Gerstel Dual Head MPS 2 autosampler
• Gerstel mVorx mixing module
• Agilent 7890 GC with multimode inlet (MMI)
• Agilent 7000C Triple Quadrupole Mass Spectrometer
• Maestro control software

Main Results and Discussion

The method demonstrated excellent linearity for all target analytes, with correlation coefficients (r2) exceeding 0.995 for representative compounds such as 1,2,4-trichlorobenzene, HCH isomers, dichlobenil, and cypermethrin. Precision of internal standards across six calibration levels yielded relative standard deviations below 5%. MRM chromatograms at the lowest level (10 ng/L) showed clear, well-resolved peaks for 12 selected pesticides, confirming adequate sensitivity.

Quadratic calibration was applied for a subset of analytes with slight non-linearity, while most pesticides fitted a linear model forced through the origin. The fully automated workflow reduced manual intervention, minimized solvent consumption, and ensured reproducible recoveries.

Benefits and Practical Applications of the Method

• High throughput: Automated extraction allows processing of large sample batches with minimal operator time.
• Enhanced reproducibility: Precise control of mixing and solvent handling improves method robustness.
• Low detection limits: Reliable quantification at 10 ng/L supports stringent regulatory requirements.
• Scalability: The protocol can be adapted for other non-polar contaminants in environmental matrices.

Future Trends and Potential Applications

Further developments may focus on reducing extraction solvent volumes to increase concentration factors and lower detection limits. Integration with more sensitive MS platforms (e.g., Agilent 7010 QQQ) could expand analyte scope and improve quantification of ultra-trace residues. Adaptation to emerging sample types such as wastewater effluents or biota extracts represents a promising avenue for environmental monitoring.

Conclusion

The fully automated liquid-liquid extraction coupled with GC-MS/MS provides a robust, reproducible, and sensitive approach for routine analysis of non-polar pesticides in water. Its streamlined workflow meets the demands of environmental and regulatory laboratories by delivering consistent performance, reduced solvent use, and high sample throughput.

Reference

No formal literature references were provided in the original text.