Analysis of Residual Pesticides in Strawberries using the Quadrupole Time-of-Flight Mass Spectrometer

Significance of the topic

Ensuring the safety of fresh produce requires sensitive and comprehensive methods to detect residual pesticides. Traditional triple-quadrupole MS techniques offer high sensitivity for targeted compounds but are limited in the number of analytes monitored simultaneously. High-resolution quadrupole time-of-flight (Q-TOF) MS expands screening capabilities by capturing full-scan data with accurate mass measurements, enabling both targeted quantitation and retrospective analysis of unexpected contaminants.

Objectives and Study Overview

This study demonstrates a workflow for multi-residue analysis of 54 common pesticides in strawberries using a Shimadzu UHPLC system coupled to a Q-TOF mass spectrometer. Key goals included evaluating calibration linearity, recovery, reproducibility, mass accuracy, and noise reduction in complex fruit matrices.

Methodology

Sample preparation and cleanup followed the QuEChERS EN 15662 protocol combined with a SPEEDIA membrane filtration kit. Strawberry homogenates (10 g) were spiked with pesticide standards, extracted with acetonitrile, partitioned by QuEChERS salts, and filtered. Final sample concentration was 0.25 g/mL with 2.5 ppb of each pesticide.
Chromatographic separation was performed on a Shim-pack Velox Biphenyl column (150 × 2.1 mm, 2.7 µm) using a gradient of 2 mM ammonium formate with 0.002% formic acid in water (A) and methanol (B). Flow rate was 0.4 mL/min, column temperature 35 °C, and injection volume 2 µL co-injected with 40 µL water.

Used Instrumentation

• UHPLC Nexera X3 system (Shimadzu)
• LCMS-9030 Q-TOF mass spectrometer with ESI in positive mode
• QuEChERS EN 15662 extraction salts kit
• SPEEDIA residual pesticides purification kit (membrane filtration)

Main Results and Discussion

• All 54 pesticides were detected at 2.5 ppb in both solvent and strawberry extract with minimal matrix interference.
• Extracted ion chromatograms (XIC) with a narrow ±5 ppm mass window reduced noise and foreign peaks compared to ±20 ppm.
• Calibration curves (0.25–50 ppb in solvent; 0.25–25 ppb in extract) exhibited excellent linearity (R² ≥ 0.99).
• Spike-and-recovery tests yielded 70–120% recovery for 50 of 54 compounds; reproducibility was generally <10% RSD.
• Mass error remained within ±1 mDa, demonstrating high mass accuracy suitable for confirmation of analytes.

Benefits and Practical Applications

• Rapid and simplified sample preparation combining QuEChERS and membrane filtration.
• Comprehensive multi-residue screening in a single run without preselection of targets.
• High sensitivity and mass accuracy support both quantitative monitoring and qualitative confirmation.
• Suitable for routine food safety testing, QA/QC in agricultural industries, and regulatory compliance.

Future Trends and Potential Applications

Advancements may include automated high-throughput workflows, expansion of pesticide libraries for retrospective screening, integration with data-processing algorithms and AI for pattern recognition, and application to a wider range of food matrices and environmental samples. Coupling Q-TOF with ambient ionization techniques could further reduce sample preparation time and broaden on-site testing capabilities.

Conclusion

The presented UHPLC-Q-TOF method enables fast, simple, and precise multi-residue analysis of pesticides in strawberries. By leveraging full-scan high-resolution MS and streamlined cleanup, this approach overcomes limitations of traditional targeted methods and offers a powerful tool for comprehensive food safety monitoring.