Analysis of Pesticide Residues in JonaGold Apples Using QuEChERS Approach and Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry (GCxGC-TOFMS)

Importance of the Topic

Pesticide residue analysis in fruits and vegetables is essential for public health and regulatory compliance. Complex matrices such as apple skins can contain sugars, fatty acids and numerous interfering compounds that challenge conventional one-dimensional GC–MS approaches. Implementing rapid extraction methods and high-resolution separations enhances detectability and reduces quantitation bias.

Study Objectives and Overview

This study evaluated a streamlined QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) extraction protocol combined with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) to screen and quantify Phosmet and Chlorpropham residues in JonaGold apple skins. The goals were to demonstrate improved separation capacity, accurate quantitation and full-range mass spectral identification without resorting to selected ion monitoring.

Methodology and Instrumentation

Sample Preparation

• Ten grams of homogenized apple skin were mixed with 10 mL acetonitrile.
• QuEChERS salts (4 g MgSO4, 1 g NaCl, 1 g trisodium citrate, 0.5 g disodium hydrogen citrate) were added and shaken.
• After centrifugation, the supernatant was directly injected into the GCxGC-TOFMS system.

Instrumentation Used

• Gas Chromatograph: Agilent 6890 with LECO consumable-free thermal modulator and secondary oven.
• Columns: Primary Rxi-5 Sil MS (15 m × 0.25 mm × 0.25 µm); secondary Rtx-200 (1.25 m × 0.18 mm × 0.18 µm).
• Modulation: Period 5 s; secondary oven offset +25 °C; modulator offset +15 °C.
• Carrier Gas: Helium at 1.5 mL/min constant flow.
• Injection: 1 µL splitless @ 250 °C, 60 s purge.
• Mass Spectrometer: LECO Pegasus 4D TOFMS; mass range 45–550 m/z; acquisition 100 spectra/s; source 225 °C.

Key Results and Discussion

GCxGC provided enhanced peak capacity and cryo-focusing that resolved Phosmet and Chlorpropham from coeluting matrix peaks visible in one-dimensional GC. Calibration curves for Phosmet (60–600 ng/mL, r²=0.997) and Chlorpropham (60–600 ng/mL, r²=0.999) showed excellent linearity. Quantitative analysis of unwashed versus washed skins indicated Phosmet levels of ~18 ng/g and 13 ng/g, respectively, while Chlorpropham was detected at 0.1 ng/g in unwashed samples and not detected after washing.

Benefits and Practical Applications

Combining QuEChERS and GCxGC-TOFMS accelerates sample throughput, reduces extensive clean-up steps and ensures unequivocal compound identification using full-range mass spectra. This workflow is suitable for routine monitoring labs, QA/QC in agro-industry and regulatory agencies.

Future Trends and Potential Applications

Emerging developments include integrating advanced data deconvolution algorithms, coupling with high-resolution accurate-mass detectors, extending the method to a broader pesticide panel and leveraging machine learning for automated peak identification and quantitation.

Conclusion

The presented approach demonstrates that rapid QuEChERS extraction paired with comprehensive GCxGC-TOFMS delivers high sensitivity, robust separation and reliable quantitation of pesticide residues in complex fruit matrices, supporting faster decision-making in food safety analysis.

References

No external literature references were provided.