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

Significance of the Topic

The prevalence of pesticide use to ensure food security has led to concerns about residual levels in produce. Sensitive and comprehensive analytical techniques are essential to monitor and enforce regulatory maximum residue limits and to safeguard public health. High-resolution full scan mass spectrometry allows broad screening of known and unexpected contaminants in complex matrices like strawberries, complementing targeted triple quadrupole methods.

Objectives and Study Overview

This study aimed to develop and validate a rapid, simple, and high-precision workflow for comprehensive detection of 54 pesticide residues in strawberries. Using QuEChERS extraction combined with SPEEDIA cleanup, samples were analyzed by a quadrupole time-of-flight LC-MS system to assess sensitivity, linearity, recovery, and reproducibility across a range of concentrations.

Methodology

Homogenized strawberry samples were spiked with a multi-pesticide standard and extracted via EN 15662 QuEChERS using magnesium sulfate, sodium chloride, and citrate buffers. The acetonitrile layer was purified through a SPEEDIA membrane cartridge and diluted prior to injection. Calibration curves were prepared in both solvent and matrix over concentration ranges from 0.25 to 50 ppb.

Instrument Used

• UHPLC: Nexera X3 system with Shim-pack Velox Biphenyl column (100 mm × 2.1 mm, 2.7 μm)
• Mobile phases: 2 mM ammonium formate/0.002% formic acid in water (A) and in methanol (B)
• Gradient: 3–10% B in 1 min, 55% at 3 min, 100% at 10.5–12 min, return to 3% at 12.01 min, 0.4 mL/min
• Injection: 2 µL (co-injection with 40 µL water)
• Mass spectrometer: Shimadzu LCMS-9030 Q-TOF, positive ESI, m/z 50–950

Key Findings and Discussion

All 54 pesticides were clearly detected at 2.5 ppb in full scan mode, with distinct chromatographic peaks and accurate extracted ion chromatograms. Calibration curves in solvent and extract exhibited excellent linearity (R2 >= 0.99) across the tested ranges. Spike recovery at 2.5 ppb showed 70–120% recovery for 50 compounds with reproducibility (%RSD) below 10% and mass errors less than 1 mDa, indicating minimal matrix interference and reliable quantitation.

Benefits and Practical Applications

• Accurate compound identification via exact mass and retention time.
• Comprehensive screening in a single analytical run.
• Streamlined and rapid sample preparation through QuEChERS and SPEEDIA.

Future Trends and Potential Applications

Expanding high-resolution full scan approaches to wider pesticide panels and diverse food matrices will strengthen monitoring programs. Coupling with advanced data processing and non-targeted analysis can reveal emerging contaminants. Further automation and miniaturization of sample preparation promise increased throughput for routine quality control.

Conclusion

The combination of QuEChERS extraction, SPEEDIA cleanup, and LCMS-9030 full scan analysis provides a fast, user-friendly, and highly precise method for detecting pesticide residues in strawberries. This workflow meets stringent regulatory standards and can be adapted to broader food safety and screening applications.