Analysis of Pesticides in Brewed Green Tea by SBSE-GCxGC-TOFMS Showing Baseline Resolution of Three Pesticides in the 2 Dimension Separation

Importance of the Topic

Monitoring pesticide residues in brewed green tea is essential for protecting consumer health and complying with regulatory limits. Complex beverage matrices demand highly sensitive and selective analytical methods to detect trace-level contaminants and ensure product quality.

Objectives and Overview of the Study

This application snapshot illustrates the combined use of stir bar sorptive extraction (SBSE), comprehensive two-dimensional gas chromatography (GC×GC), and time-of-flight mass spectrometry (TOFMS) to analyze three pesticides—disulfoton, e-lindane, and diazinone—spiked at 250 parts per trillion (ppt) into brewed green tea. The primary goal is to demonstrate baseline separation and reliable quantitation in a complex matrix.

Methodology and Instrumentation

Target analytes were preconcentrated from brewed green tea using SBSE, followed by thermal desorption into a GC×GC system. The first-dimension column (10 m × 0.18 mm × 0.2 µm Rtx-5) provides initial separation, while the second-dimension column (1.5 m × 0.10 mm × 0.10 µm DB-17) achieves orthogonal resolution. An TOFMS detector scanned from m/z 45 to 550 at 150 spectra per second, enabling accurate mass measurement.

Used Instrumentation

• SBSE sampling device for trace enrichment
• GC×GC system with Rtx-5 and DB-17 capillary columns
• Time-of-flight mass spectrometer operating at 150 spectra/s over m/z 45–550

Main Results and Discussion

The reconstructed first-dimension chromatogram shows complete coelution of all three pesticides, identified by unique ions m/z 137 (disulfoton), m/z 88 (e-lindane), and m/z 111 (diazinone). A three-dimensional contour plot from the second-dimension separation confirms baseline resolution of the analytes. The method achieves reproducible detection at the 250 ppt level within a complex tea matrix.

Benefits and Practical Applications

The SBSE-GCxGC-TOFMS workflow offers:

• Enhanced sensitivity through preconcentration
• Superior chromatographic resolution in two dimensions
• Rapid mass spectral acquisition for clear identification
• Suitable for routine food safety and environmental testing laboratories

Future Trends and Applications

Advances may include faster TOFMS acquisition rates, coupling with high-resolution mass spectrometry, expansion to a broader range of pesticides, and adaptation for high-throughput screening in industrial quality control.

Conclusion

This study demonstrates that SBSE coupled with GC×GC-TOFMS delivers robust, sensitive, and selective analysis of trace-level pesticides in brewed green tea, achieving baseline separation and reliable quantitation in a challenging matrix.

Reference

Application Snapshot, Life Science and Chemical Analysis Centre, LECO Corporation; Form No. 209-200-132; October 2008.