Simultaneous determination of pesticide residues in vegetable extract by liquid chromatograph tandem mass spectrometry for high recovery rate

Importance of the topic

The accurate and simultaneous analysis of multiple pesticide residues in vegetables is critical for ensuring food safety, complying with regulatory standards, and protecting public health. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) has become a powerful tool for multi-residue detection owing to its sensitivity and selectivity, but matrix effects often impair quantitative accuracy. This study addresses these challenges by optimizing analytical parameters to achieve high recovery and reproducibility using an absolute calibration approach.

Objectives and study overview

The main objective was to develop a rapid LC–MS/MS method capable of detecting and quantifying 89 pesticide residues in vegetable extracts with high recovery rates. The work included evaluation of electrospray ionization conditions, flow rate and probe position adjustments, and assessment of linearity, sensitivity, and repeatability under absolute calibration, avoiding the need for matrix-matched curves.

Methodology and instrumentation used

Sample Preparation:

• Carrot extract prepared by QuEChERS SPE (STQ method).
• Blank matrix spiked with pesticide standards (PL-7-2, PL-14-2, PL-15-1).

Chromatography and Mass Spectrometry:

• LC: Shim-pack Scepter C18 column (100×2.0 mm, 1.9 μm), mobile phases 5 mM ammonium acetate in water and methanol, gradient over 32 min.
• Flow rate varied between 0.2 and 0.4 mL/min; column at 40 °C; injection volume 5 μL.
• MS: Shimadzu LCMS-8050 with Nexera X2 UHPLC; ESI in positive/negative MRM mode; rapid polarity switching; detailed parameters optimized for probe position (2–3 mm), gas flows and temperatures.

Main results and discussion

Linearity and quantification ranges:

• 89 compounds linear from 0.1–20 ng/mL; 78 compounds linear up to 50 ng/mL.
• Analysis time: 32 min including column re-equilibration.

Recovery and repeatability:

• Optimal conditions at 0.4 mL/min and 3 mm probe distance yielded recovery rates of 85–120% for most analytes and RSDs below 5%.
• Increased flow rate reduced raw signal but improved reproducibility when combined with extended probe position.

Representative MRM chromatograms confirmed consistent peak shapes and sensitivities for low-abundance analytes.

Benefits and practical applications of the method

This optimized LC–MS/MS protocol allows high-throughput, reliable multi-residue pesticide monitoring in vegetable matrices without time-consuming matrix-matched calibration. It supports regulatory compliance under positive list systems and enhances laboratory productivity in food safety testing.

Future trends and opportunities

Further developments may include:

• Integration with high-resolution mass spectrometry for suspect screening and non-targeted analysis.
• Automation of sample preparation and data processing using AI-driven software.
• Extension to diverse matrices such as fruits, grains, and processed foods.
• Miniaturization of ion sources and microflow LC for enhanced sensitivity and reduced solvent use.

Conclusion

A robust LC–MS/MS method was established for simultaneous quantification of 89 pesticide residues in vegetable extracts. By optimizing flow rate and ESI probe position, the approach delivers high recovery and reproducibility using absolute calibration, streamlining multi-residue analysis for routine food safety monitoring.