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

Significance of the Topic

Cucumber is a popular fresh-eaten commodity valued for its crisp texture and high water content. Ensuring the absence of harmful pesticide residues in cucumbers is essential for consumer safety and regulatory compliance. This requires sensitive, reliable, and high-throughput analytical methods capable of screening hundreds of compounds against strict maximum residue limits (MRLs) set by the European Union and other authorities.

Objectives and Study Overview

This study aimed to validate a comprehensive multi-residue method for the determination of 513 pesticide residues in cucumber using LC-MS/MS on Shimadzu LCMS-8060NX and 308 residues by GC-MS/MS on Shimadzu GCMS-TQ8040NX. The work was conducted in collaboration with Shimadzu Middle East and Africa FZE, the Saudi Food and Drug Authority (SFDA), and AnalyticaOne.

Methodology and Instrumentation

The QuEChERS extraction technique with dispersive SPE clean-up was applied to cucumber samples. Key steps and parameters included:

• Extraction: Acetonitrile with MgSO4, NaCl and citrate buffers.
• Clean-up: PSA and MgSO4 followed by 0.2 µm filtration.
• Internal standards: Chlorpyrifos-D10 and Triphenyl phosphate for LC-MS/MS; PCB-18 for GC-MS/MS.
• Calibration: Matrix-matched standards spiked at 1–75 µg/L (LC-MS/MS) and 1–100 µg/L (GC-MS/MS) using weighted 1/C² regression.
• LC conditions: Shim-pack Velox Biphenyl column (2.1 × 100 mm, 2.7 µm), mobile phases A (water + 2 mM ammonium formate, 0.01% formic acid) and B (methanol + 2 mM ammonium formate, 0.01% formic acid), gradient from 3% to 100% B, flow rate 0.4 mL/min, injection 4 µL with co-injection of water, ESI positive/negative, interface 350 °C.
• GC conditions: SH-Rxi-5Sil MS column (30 m × 0.25 mm i.d., 0.25 µm), splitless injection (1 µL), helium carrier, oven program from 105 °C to 290 °C, ion source 230 °C.
• Data acquisition: Target and two reference MRM transitions managed by LabSolutions Insight software.

Used Instrumentation

• Shimadzu LCMS-8060NX with LC-40 series pump and SIL-40 autosampler
• Shimadzu GCMS-TQ8040NX triple quadrupole GC-MS/MS system
• Shim-pack Velox Biphenyl LC column and SH-Rxi-5Sil MS GC column
• LabSolutions Insight data processing software

Main Results and Discussion

Matrix-matched calibration curves exhibited excellent linearity (R² > 0.995) over the working range. Accuracy for all standards fell within 80–120% per SANTE guidelines. Recovery studies at 10, 20 and 50 µg/kg (LC) and 10 and 20 µg/kg (GC) showed mean recoveries of 70–120% for most analytes; a few compounds fell below 70% but remained reproducible. Repeatability and reproducibility at the limit of quantification (LOQ) levels demonstrated %RSD values below 20%. The use of co-injection improved early eluting polar peaks and addition of water to the QuEChERS protocol enhanced recoveries of certain GC-amenable pesticides.

Benefits and Practical Applications

• Simultaneous quantification of over 600 pesticides in a single workflow
• High sensitivity and specificity meeting regulatory MRL requirements
• Robust sample preparation suitable for high-water matrices
• Streamlined data processing for fast decision-making in QA/QC and food safety laboratories

Future Trends and Opportunities

Advances in high-resolution mass spectrometry and rapid screening techniques will further expand the scope of multi-residue analysis. Integration of automated sample preparation and machine learning–driven data interpretation can enhance throughput and reduce human error. Development of comprehensive spectral libraries and miniaturized instruments will open new applications in field-based monitoring and real-time food safety assessment.

Conclusion

A robust, validated LC-MS/MS and GC-MS/MS method has been established for the analysis of more than 600 pesticide residues in cucumber. The approach meets international guidelines, delivers reliable accuracy and precision, and supports regulatory compliance and consumer safety.

Reference

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, 2007.