Validation of the Method for Determination of Pesticide Residues by Gas Chromatography – Triple-Stage Quadrupole Mass Spectrometry

Significance of the topic

Pesticide residue analysis in food is a cornerstone of consumer safety and regulatory compliance. As European regulations impose increasingly stringent maximum residue limits (MRLs), analytical laboratories must deploy highly sensitive and selective methods to detect trace levels of multiple pesticides across diverse food matrices.

Objectives and study overview

This work presents an in-house validation of a complete multi-residue workflow for approximately 140 priority pesticides in strawberry, wheat flour and leek. The goals were to demonstrate compliance with European guidelines (Regulation 396/2005, Directive 2006/125/EC and SANCO requirements) and confirm method sensitivity down to the required limits of quantification (LOQs).

Used Instrumentation

• Thermo Scientific TRACE 1310 Gas Chromatograph with PTV splitless injector
• Thermo Scientific TSQ 8000 Triple-Stage Quadrupole GC-MS System (Pesticide Analyzer)
• Thermo Scientific TraceFinder 3.1 Software for data acquisition and review
• Thermo Fisher QuEChERS extraction and clean-up kits (50 mL and 15 mL)
• Ultra-Turrax homogenizer, Fisher and Sartorius analytical balances
• Vortex shakers, microcentrifuge and standard lab consumables

Methodology

A QuEChERS-based sample preparation was employed: 10 g homogenized sample was extracted with buffered salts (MgSO4, NaCl, citrate salts) and acetonitrile spiked with internal standards (triphenylphosphate, bromo-fluorobenzene). After 10 min shaking and centrifugation, the supernatant was cleaned using PSA and C18 sorbents. Samples were fortified with sorbitol protectant and injection standard, then analyzed by GC-MS/MS in timed-SRM mode. The GC oven ramped from 40 °C to 300 °C, while the MS operated in EI+ with optimised collision energies and ion transitions for each pesticide.

Main Results and Discussion

• Selectivity: All target analytes demonstrated resolved chromatographic peaks with at least one quantifier and two qualifier transitions. Ion ratios and retention times met SANCO criteria, with resolution factors >1.5 for co-eluting compounds.
• Linearity and matrix effects: Six-point, matrix-matched calibrations yielded correlation coefficients (r²) >0.99 for most analytes. Minor to moderate matrix effects were corrected by using matrix-matched standards.
• Accuracy and precision: Recoveries ranged from 70–120% at low, intermediate and high spike levels (10, 20 and 100 ng/g), with within- and between-day RSDs generally <20%.
• LOD/LOQ: Method detection and quantification limits were at or below legislative MRLs for the majority of compounds. A default LOQ of 10 ng/g was applied where no specific MRL exists.
• Robustness: Variations in operator, reagent batches and clean-up tubes did not significantly affect results, confirming method resilience.

Benefits and practical applications of the method

This validated workflow delivers a turnkey solution for routine multi-residue pesticide screening in compliance with EU regulations. High throughput and automated data processing enable efficient QA/QC in food safety laboratories, covering a broad analyte spectrum with consistent performance.

Future trends and potential applications

Advances in MS technology, including higher-sensitivity detectors and high-resolution mass spectrometry, will expand the target pesticide range and lower detection limits further. Integration of AI-driven data analysis and non‐target screening capabilities is expected to enhance monitoring of emerging contaminants and fraudulent pesticide use.

Conclusion

The in-house validation confirms that the combined QuEChERS sample preparation and Thermo Scientific TSQ 8000 GC-MS/MS platform meets stringent regulatory requirements for multi-residue pesticide analysis. While the majority of compounds are reliably quantified, certain analytes with strong matrix interferences or elevated LOQs may require tailored clean-up strategies.

References

• European Commission 2002/657/EC
• European Commission 2006/125/EC
• European Commission SANCO/12495/2011
• European Commission 788/2012/EC
• Fussell et al. (2007) Food Additives & Contaminants, 24:1247–1256
• Thermo Scientific TSQ 8000 Pesticide Analyzer Brochure
• EU Pesticides Database (ec.europa.eu)
• Anastassiades et al. (2003) Journal of Chromatography A, 1015:163–184