Analysis of Phytosanitary Products in Surface Water and Groundwater Using GCxGC-TOFMS

Significance of the Topic

Phytosanitary products applied in agriculture and related sectors often leach into surface and groundwater, posing risks to ecosystems and human health. Regulatory limits for individual pesticide residues in water are set at 0.1 µg/L and 0.5 µg/L for total concentrations, driving the need for highly sensitive and selective analytical methods.

Objectives and Study Overview

This study aimed to develop and validate a method for simultaneous detection and quantification of 51 phytosanitary compounds in environmental water samples. The approach employed solid-phase extraction for sample cleanup and enrichment, followed by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GCxGC-TOFMS).

Methodology and Instrumentation

Environmental water samples (500 mL) were spiked with a deuterated process standard and extracted using an OASIS HLB SPE cartridge. Elution was performed with ethyl acetate, and the extract was concentrated and spiked with an internal standard. Quantitative calibration covered six levels from 0.01 to 0.15 µg/L. Analysis was conducted on a Pegasus BT 4D GCxGC-TOFMS system equipped with an Agilent 7890 GC and dual stages of thermal modulation. A non-polar Rxi-5MS primary column and a polar Rxi-17Sil secondary column provided multidimensional separation. Mass spectra were acquired at 150 Hz over m/z 40–500 and processed using ChromaTOF software with the Target Analyte Finding method.

Main Results and Discussion

One-dimensional GC-TOFMS showed extensive coelutions among pesticide analytes. In contrast, GCxGC-TOFMS achieved baseline separation of all 51 targets, with clear resolution demonstrated for critical pairs such as chlorpyrifos-methyl vs vinclozolin and Ametryn vs Alachlor vs Heptachlor. Spectral deconvolution in 1D provided some resolution but with lower library match scores. The 2D approach improved mass spectral similarity by up to 60 points and increased signal-to-noise ratios by factors of 1.7 to 6.2. Method validation following Eurachem guidelines yielded correlation coefficients (R2) between 0.9919 and 0.9998, limits of detection from 0.0005 to 0.0033 µg/L, and limits of quantification from 0.0016 to 0.0099 µg/L. Precision and accuracy metrics met acceptance criteria, and recoveries ranged from 65 % to 109 %. Analysis of fourteen real water samples revealed average total pesticide concentrations of 0.070 µg/L in groundwater and 0.314 µg/L in surface water, with two samples exceeding the 0.5 µg/L threshold.

Benefits and Practical Applications

• Enhanced chromatographic resolution eliminates coelutions of structurally similar pesticides
• Improved sensitivity supports trace-level quantification below regulatory limits
• Comprehensive screening allows retrospective analysis of archived data for emerging contaminants
• Robust validation ensures reliable monitoring in QA/QC and environmental surveillance

Future Trends and Opportunities

Advancements in GCxGC-TOFMS are expected to expand target lists to include novel and emerging agrochemicals. Integration with machine learning algorithms could streamline data processing and peak identification. Portable multidimensional GC instruments may enable field-based screening, enhancing rapid decision making in environmental monitoring.

Conclusion

The developed SPE–GCxGC-TOFMS method provides a validated, high-performance platform for simultaneous analysis of 51 phytosanitary products in water. Its superior separation and sensitivity make it ideal for regulatory compliance and environmental risk assessment.

References

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