Pesticide Target Screening with GC-APCI coupled to high-resolution QTOF-MS

Significance of the Topic

The reliable detection of pesticide residues in food and environmental matrices is essential for safeguarding public health, meeting regulatory requirements, and supporting sustainable agricultural practices. Combining chromatographic separation with high-resolution accurate mass detection enhances the scope of screening methods to cover a broad range of semi-volatile, polar, and thermo-labile compounds in a single workflow.

Objectives and Study Overview

This work presents the first application of gas chromatography coupled to atmospheric pressure chemical ionization and quadrupole time-of-flight mass spectrometry (GC-APCI-QTOF-MS) with alternating full scan and broadband collision-induced dissociation (bbCID) for targeted pesticide screening. A representative mixture of 60 pesticides was selected to optimize fast chromatographic separation, evaluate limits of detection and quantification, and assess matrix effects in fruit extracts.

Methodology

• Sample Preparation: QuEChERS extracts of orange, peach, and tomato were spiked at levels from 0.01 to 1000 ng/mL, yielding calibration curves across two to three orders of magnitude.
• Chromatography: A 30 m Rxi-5 ms capillary column was operated under a temperature gradient from 70 °C to 300 °C, helium flow at 1.2 mL/min, and pulsed splitless injection of 2 µL.
• Mass Spectrometry: Data acquisition from m/z 50–1000 at ≥8 Hz with alternating full scan and bbCID in positive APCI mode, externally calibrated with PFTBA.
• Data Processing: Target identification based on retention time, accurate monoisotopic masses, isotope patterns, and diagnostic fragment ions, using DataAnalysis 4.3 and TASQ 1.0 with stringent extraction windows (±3 mDa, ±0.7 min).

Used Instrumentation

• Gas Chromatograph: Bruker 456-GC with PAL Combi-xt autosampler
• Ion Source: Bruker GC-APCI II
• Mass Spectrometer: Bruker impact II QTOF
• Software: DataAnalysis 4.3, TASQ 1.0

Main Results and Discussion

Out of 60 pesticides, 48 were consistently detected and quantified with limits of quantification ranging from 0.1 to 50 ng/mL. The majority of chromatographic peaks exhibited full width at half maximum (FWHM) below 2 s, underscoring the necessity of ≥8 Hz acquisition for accurate peak definition. Linear dynamic ranges spanned at least two orders of magnitude (R² > 0.99), and average mass accuracies remained below 0.9 ppm even in complex fruit matrices. Matrix interferences were minimal, demonstrating the selectivity of GC-APCI ionization and high-resolution MS separation.

Benefits and Practical Applications

• Comprehensive Coverage: Simultaneous screening of semi-volatile and polar pesticides in a single run.
• High Selectivity: Accurate mass and diagnostic fragments enable confident identification in complex matrices.
• Rapid Analysis: Fast chromatographic gradients and high-speed acquisition increase sample throughput.
• Retrospective Data Mining: Full scan bbCID data allow post-acquisition interrogation for emerging contaminants.

Future Trends and Potential Applications

Advancements may include expansion of pesticide libraries, integration with automated sample preparation, coupling to orthogonal ionization sources, and deployment in monitoring networks for real-time surveillance of contamination in food supply chains. Machine-learning algorithms applied to full scan datasets could further improve screening accuracy and predict unknown residues.

Conclusion

The study demonstrates that GC-APCI-QTOF-MS with alternating full scan and bbCID is a robust platform for targeted pesticide screening, delivering low detection limits, broad dynamic range, high mass accuracy, and minimal matrix effects. Fast data acquisition and accurate mass measurements support reliable quantification and identification in routine food safety and environmental analysis.