Determination of Pesticide Residues in Cucumber Using GC-MS/MS With APGC™ After Extraction and Clean-up Using QuEChERS

Importance of the Topic

Monitoring pesticide residues in food commodities is critical for public health, trade compliance, and regulatory enforcement. Cucumber, a widely consumed vegetable, requires reliable multiresidue methods to detect hundreds of GC-amenable pesticides at concentrations below established maximum residue limits (MRLs).

Objectives and Study Overview

This work aimed to develop and validate a comprehensive GC-MS/MS method using atmospheric pressure gas chromatography (APGC) coupled to a Xevo TQ-XS system for over 200 pesticide residues in cucumber. The method integrates a QuEChERS extraction and dispersive SPE clean-up to provide high throughput, sensitivity, and specificity.

Methodology and Instrumentation

Sample Preparation and Clean-up:

• Homogenize cucumber and freeze until analysis.
• Apply CEN QuEChERS extraction in acetonitrile, followed by dispersive SPE clean-up.
• Prepare matrix-matched calibration standards (0.0005–0.10 mg/kg) using a multiresidue pesticide kit.

GC-MS/MS Conditions:

• Gas chromatograph: Agilent 7890A with CTC CombiPal autosampler.
• Column: Restek Rxi-5Sil MS, 30 m × 0.25 mm × 0.25 μm.
• Injection: 1 µL splitless, 250 °C, helium carrier at 2 mL/min.
• Oven program: 90 °C (1 min) to 330 °C at 8.5 °C/min, hold 5 min.
• Mass spectrometer: Waters Xevo TQ-XS with APGC source, water modifier, source at 150 °C, corona current 2 µA.
• Data acquisition: MassLynx v4.2 and TargetLynx XS for MRM transitions.

Used Instrumentation

• Agilent 7890A GC system
• CTC CombiPal autosampler
• Restek Rxi-5Sil MS column
• Waters Xevo TQ-XS triple quadrupole with APGC
• MassLynx and TargetLynx software

Main Results and Discussion

• Chromatographic performance achieved ≥12 data points per peak and clear separation of >200 analytes at 0.001 mg/kg.
• Detection limits:  LOD < 0.0005 mg/kg for 85% of pesticides; two analytes not detected at lowest level.
• Calibration: r² > 0.99 for most compounds; a few required exclusion of low-level points to meet SANTE residual criteria.
• Recoveries: 94% of analytes between 70–120% at 0.001 mg/kg; repeatability (RSDr) ≤ 20% for 99% of analytes.
• Reference material (cucumber puree) confirmed method accuracy and precision; minor losses observed for unstable compounds (e.g., tolylfluanid).

Benefits and Practical Applications

• APGC offers enhanced selectivity and sensitivity compared to traditional EI ionization, enabling detection at sub-MRL levels without solvent exchange or large volume injections.
• Single-injection workflow with QuEChERS extraction provides cost-effective, high-throughput analysis suitable for routine monitoring by regulatory, industry, and contract laboratories.

Future Trends and Opportunities

Emerging advances in ionization, automation, and data processing will further lower detection limits, expand analyte scope, and improve throughput. Integration with high-resolution MS and application to diverse matrices will broaden compliance monitoring, environmental testing, and pesticide fate studies.

Conclusion

The validated GC-MS/MS method with APGC detection delivers sensitive, specific, and accurate quantification of over 200 pesticide residues in cucumber down to 0.0005 mg/kg. The approach meets SANTE guidelines for recovery and repeatability, and is adaptable to other commodities for MRL enforcement.

References

1. Niu Y et al. Trends Anal. Chem. 2020;132:116053.
2. Cherta L et al. J Chromatogr. A 2013;1314:224–240.
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4. Saito-Shida S et al. Food Addit. Contam. A 2020b;38(1):125–135.
5. CEN EN 15662:2018. Foods of Plant Origin—Multimethod for Pesticide Residues.
6. SANTE/12682/2019. Guidance Document on Analytical Quality Control.