Rapid Analysis of Pesticides in DifficultMatrices Using GC/MS/MS

Importance of the Topic

The determination of pesticide residues in complex food matrices such as fruit preserves is critical for consumer safety and regulatory compliance. Regulations like EU 396/2005 set maximum residue limits (MRLs) typically at 0.01 mg/kg for more than 500 pesticides, demanding analytical methods that combine sensitivity, selectivity, speed and cost-efficiency.

Objectives and Overview of the Study

This application note describes a rapid multi-residue procedure for determining 96 GC-amenable pesticides and transformation products in fruit jam. The goals were to meet EU regulatory performance criteria, simplify sample preparation, minimize matrix effects, and enable fast (< 48 h) turnaround using a generic QuEChERS extract coupled with GC-tandem mass spectrometry.

Methodology

Fruit jam (10 g) was homogenized with water and acetonitrile containing triphenylphosphate as internal standard. After shaking, citrate buffer salts (MgSO4, NaCl, disodium hydrogen citrate, trisodium citrate) were added, followed by dispersive SPE cleanup using MgSO4 and PSA sorbent. A 1 mL aliquot of the cleaned extract was acidified and injected (1 µL) splitlessly into the GC-MS/MS system. Final extract concentration corresponded to 1 g sample per mL acetonitrile.

Used Instrumentation

• GC-MS/MS: Thermo Scientific TSQ Quantum XLS with EI source (70 eV) in SRM mode.
• Autosampler: TriPlus liquid sampler with splitless injector at 225 °C.
• Column: TR-Pesticide, 30 m × 0.25 mm, 0.25 µm film; He carrier gas (1 mL/min).
• Oven: 60 °C initial, ramp to 290 °C, total run ~57 min.
• Collision gas: Argon at 1 mTorr; Q1/Q3 resolution 0.7 u FWHM.

Main Results and Discussion

Method validation using matrix-matched standards spiked between 0.01–0.05 mg/kg (seven compounds at higher levels) demonstrated:

• Recoveries: 80–110% for most analytes; chlorothalonil at 63% at 0.01 mg/kg (screening-suitable).
• Precision: CVs < 15%; typically < 10%.
• Linearity: r2 > 0.98 across calibration ranges.
• Limits of detection: ~0.005 mg/kg (signal/noise > 5:1).
• High selectivity: no significant interferences in SRM chromatograms.

Direct low-volume injection avoided losses of volatile pesticides and column damage, while matrix calibration compensated residual effects.

Benefits and Practical Applications

This simplified QuEChERS-GC/MS/MS approach:

• Reduces sample preparation time and solvent consumption.
• Eliminates evaporation and solvent exchange steps.
• Achieves regulatory MRL compliance for a broad pesticide panel.
• Offers rapid turnaround suitable for routine monitoring in food safety, QA/QC laboratories, and regulatory agencies.

Future Trends and Potential Applications

Further improvements may include integration with automated sample preparation, expansion of target lists including emerging transformation products, and coupling with high-resolution MS for non-target screening. Advances in ion sources and software will enhance sensitivity and throughput, supporting large-scale monitoring and rapid incident response.

Conclusion

The combination of citrate-buffered QuEChERS extraction with splitless GC-MS/MS on the TSQ Quantum XLS delivers a robust, fast and sensitive multi-residue method for challenging matrices such as fruit jam. Performance meets EU requirements for most pesticides at 0.01 mg/kg, with streamlined workflows and minimized matrix impacts.

Reference

1. EC Regulation 396/2005
2. Anastassiades et al., J. AOAC Int., 86(2), 412 (2003)
3. QuEChERS citrate-buffered procedure
4. EU DG SANCO Document 10684/2009
5. Godula et al., J. High Resol. Chromatogr., 22(7), 395–402 (1999)
6. Hajšlová et al., J. Chromatogr. A, 800(1998), 283–295