A Comparative Study of Targeted Screening Method by LC/MS/MS and Un-targeted Screening Method by LC-TOF in Residual Pesticides Analysis

Significance of the topic

Screening for pesticide residues in food and agricultural products is critical for consumer safety, compliance with regulatory limits and public health. Modern liquid chromatography–mass spectrometry (LC–MS) techniques provide both targeted and untargeted approaches to detect a broad range of compounds at trace levels. Comparing these methods reveals strengths and limitations that guide routine analysis and future developments.

Objective and study overview

This study compared two complementary screening strategies using the same unknown mixed‐pesticide samples:

• Targeted screening based on scheduled multiple reaction monitoring (MRM) on a triple quadrupole LC–MS/MS.
• Untargeted full‐scan screening with accurate high‐resolution mass detection on an LC–TOF system.

The goal was to assess sensitivity, identification reliability and workflow efficiency for pesticide residue analysis.

Methodology and instrumentation

• LC–MS/MS (Shimadzu LCMS‐8050): Ultrafast MRM in positive/negative mode with preloaded transitions covering up to 347 pesticides in three method packages. Chromatography used a Shim-pack XR-ODS III column, 20 min gradient, 0.4 mL/min flow and electrospray ionization.
• LC–TOF (Shimadzu LCMS‐IT-TOF): High‐resolution full‐scan acquisition in multi‐event narrow mass windows (m/z 100–900 segmented into ten events). Chromatography on the same column with a 35 min gradient, 0.3 mL/min, and accurate mass measurement (±5 ppm).

Main results and discussion

• Targeted MRM screening found a total of 189 unique pesticides across three method packages.
• Untargeted HRMS screening initially detected and confirmed 83 pesticides from a 450‐compound database, with 37 additional suspects.
• Re‐interrogation of raw TOF data by extracting exact masses of MRM‐identified compounds revealed 69 more pesticides obscured by baseline noise or coelution in full‐scan mode.
• MRM provided superior detection sensitivity and automated confirmation via ion‐ratio checks, but is limited to predefined target lists.
• HRMS offers unlimited scope and retrospective data mining, yet suffers from lower sensitivity for low‐abundance peaks and challenges in reliable peak picking under matrix interferences.

Benefits and practical applications

• MRM‐based targeted screening delivers rapid, highly sensitive and fully automated analysis ideal for regulatory monitoring when target lists are well defined.
• Untargeted HRMS screening enables discovery of unexpected or novel residues and supports retrospective analysis against expanding compound databases.

Future trends and possibilities of use

Advances in data processing algorithms and hybrid acquisition modes may combine the sensitivity of MRM with the breadth of full‐scan HRMS. Machine learning–driven peak deconvolution and automated library building will further enhance untargeted workflows. Integrating both approaches in a single platform could offer comprehensive screening with minimal compromise.

Conclusion

Targeted LC–MS/MS using MRM excels in sensitivity and reliability for known pesticides, while high‐resolution LC–TOF untargeted screening provides unlimited scope but requires enhanced data analysis to reach comparable detection performance. A hybrid strategy leveraging strengths of both is recommended for comprehensive pesticide residue surveillance.

Reference

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