Method Validation for Determining 513 Pesticide Residues in Cucumber Using LCMS-8060NX and 308 Residues by GCMS- TQ8040NX

Importance of the Topic

The consumption of raw cucumbers is widespread due to their fresh taste and crisp texture. However, their high water content and direct consumption raise significant food safety concerns if pesticide residues exceed regulatory limits. The European Union has established stringent maximum residue limits (MRLs) often set at 10 µg/L, underscoring the need for comprehensive analytical methods capable of screening a large number of pesticides in cucumber matrices.

Objectives and Study Overview

This work aimed to develop and validate a multi-residue method for the quantification of 513 pesticides using LC-MS/MS (Shimadzu LCMS-8060NX) and 308 pesticides by GC-MS/MS (Shimadzu GCMS-TQ8040NX). The study focused on achieving reliable detection at or below regulatory MRLs, while streamlining sample preparation and enhancing throughput.

Materials and Methods

A modified QuEChERS extraction protocol was applied to cucumber samples, involving acetonitrile partitioning with magnesium sulfate, sodium chloride, citrate salts, followed by dispersive solid-phase extraction (dSPE) cleanup with PSA and additional salts. The final extract was filtered and, for LC-MS/MS, diluted fivefold with aqueous solvent.

• Calibration: Matrix-matched standards at 1–75 µg/L (LC-MS/MS) and 1–100 µg/L (GC-MS/MS) with weighted 1/C² regression and internal standards (Chlorpyrifos-D10, Triphenyl phosphate for LC; PCB-10 for GC).
• LC-MS/MS Conditions: Mobile phases of 2 mM ammonium formate with 0.002% formic acid in water and methanol; 15 min gradient; ESI source; 4 µL injection with co-injection feature to sharpen early-eluting peaks.
• GC-MS/MS Conditions: SH-1 5Sil MS column (30 m × 0.25 mm); 40 min oven program from 105 °C to 290 °C; splitless injection of 1 µL.

Instrumentation

• Shimadzu LCMS-8060NX coupled with Nexera LC-40 series
• Shimadzu GCMS-TQ8040NX
• LabSolutions Insight software for data processing and QA/QC flagging

Main Results and Discussion

Validation followed SANTE guidelines, assessing linearity, specificity, recovery, precision (repeatability and reproducibility), and matrix effects:

• Linearity: Calibration curves showed coefficients of determination (R²) above 0.99 for representative pesticides.
• Specificity and Precision: Method specificity confirmed against blank matrices; %RSD for 513 LC compounds and 308 GC compounds remained below 20%.
• Recovery: Mean recoveries fell between 70% and 120% at spiking levels of 10, 20, and 50 µg/kg, with few exceptions addressed by optimizing water addition during extraction.
• Limits of Quantification: Achieved LOQ of 10 µg/kg for both techniques.

Benefits and Practical Applications

This validated workflow enables testing laboratories to perform high-throughput screening of hundreds of pesticides with confidence in compliance with international MRLs. The combination of QuEChERS sample preparation, rapid instrumental methods, and automated QA/QC flagging greatly reduces analysis time and manual data review.

Future Trends and Opportunities

Emerging directions in pesticide residue analysis include:

• Integration of high-resolution mass spectrometry for non-target screening.
• Miniaturized and portable devices for on-site testing.
• Automation of sample preparation and data processing workflows.
• Machine learning algorithms for pattern recognition and predictive analytics in residue profiling.

Conclusion

The presented method demonstrates robust performance for multi-residue analysis in cucumbers, combining sensitivity, accuracy, and throughput. Adoption of these validated protocols supports regulatory compliance and enhances food safety monitoring.

References

1. EN 15662: Determination of pesticide residues using GC-MS and/or LC-MS(/MS) following acetonitrile extraction/partitioning and cleanup by dispersive SPE – QuEChERS method. European Committee for Standardization, Brussels, 2007.
2. SANTE/11312/2021: Analytical Quality Control and Method Validation Procedures for Pesticide Residue Analysis in Food and Feed.