An Optimal Method for the Analysis of Pesticides in a Variety of Matrices

Significance of the topic

The accurate determination of pesticide residues in food and environmental samples is critical for public health, regulatory compliance, and environmental protection. Matrix effects arising from complex sample compositions often compromise the reliability of multiple reaction monitoring (MRM) methods in gas chromatography–tandem mass spectrometry (GC–MS/MS). Implementing matrix-optimized MRM transitions enhances analytical accuracy, sensitivity, and laboratory throughput across diverse commodities.

Objectives and study overview

This application study evaluated an optimal workflow for screening and quantifying 195 pesticide targets in eight representative matrices: yellow onion, navel orange, organic honey, cucumber, jasmine rice, loose leaf black tea, baby spinach, and extra virgin olive oil. The goals were to identify the most robust MRM transitions for each matrix, assess calibration performance, and demonstrate method suitability at trace levels.

Methodology and instrumentation used

Sample preparation employed the QuEChERS approach with matrix-specific dispersive solid-phase extraction (dSPE) cleanup kits. Each commodity underwent vortex mixing, salting-out, centrifugation, and targeted dSPE for oils, pigments, sugars, and acids. Calibration standards ranged from 0.12 to 50 pg/µL in acetonitrile. A comprehensive GC MRM database (Agilent G9250AA P&EP Standard MRM Database) containing over 1 100 compounds and up to 10 MRMs per compound guided transition selection.

Instrumentation used

All analyses were performed on an Agilent 7890B gas chromatograph with a multimode inlet (MMI) and backflush configuration, coupled via a purged ultimate union (PUU) to an Agilent 7010A triple quadrupole GC–MS/MS system. Two HP-5 ms UI capillary columns (15 m × 0.25 mm, 0.25 µm) were employed with helium carrier gas. The mass spectrometer operated at 70 eV with wide resolution settings, time-segmented dwell times, and matrix-optimized collision gas flows.

Main results and discussion

From the initial set of five top-ranked MRM transitions per compound in solvent, three to four transitions were transferred to each matrix method. Calibration curves in each matrix achieved R² ≥ 0.990 for 90 % of targets. Repeatability, expressed as %RSD of replicate injections, was ≤ 30 % for all pesticides. Ninety percent of targets yielded limits of quantitation (LOQ) ≤ 1.5 pg/µL. Comparative chromatograms highlighted matrix effects including ion suppression, enhancement, retention time shifts, and interferences, underscoring the necessity of matrix-specific optimization.

Contributions and practical applications

• Matrix-optimized MRMs mitigate interferences and enhance confidence in quantitation of trace pesticides in complex commodities.
• Expanded MRM databases enable rapid method development and flexible transition selection tailored to regulatory requirements worldwide.
• The workflow supports high-throughput screening in food safety, environmental monitoring, and quality control laboratories.

Future trends and potential applications

Advances may include integration of high-resolution mass spectrometry to further reduce matrix background, machine-learning algorithms for automated transition optimization, miniaturized sample-preparation platforms, and expansion of spectral libraries to emerging agrochemicals. Real-time data processing and cloud-based database updates will streamline method adaptation to evolving regulatory lists.

Conclusion

Matrix-specific optimization of MRM transitions significantly improves the robustness, sensitivity, and reproducibility of pesticide analyses by GC–MS/MS. The combination of QuEChERS sample preparation, a comprehensive MRM database, and an advanced triple quadrupole system addresses the growing demands of modern agricultural testing and environmental monitoring.

References

1. Anastassiades M.; Lehotay S. J.; Štajnbaher D.; Schenck F. S. J. AOAC Int. 2003, 86, 412–431.
2. Lehotay S. J.; Mastovská K.; Lightfield A. R. J. AOAC Int. 2005, 88, 615–629.