Reduction of Matrix Effects in Liquid Chromatography‐Tandem Mass Spectrometry by a Dilution Approach for the Analysis of 245 Pesticide Residues in Selected Vegetables

Matrix effects in liquid chromatography-tandem mass spectrometry remain a significant challenge in pesticide residue analysis. Ion suppression can introduce uncertainty in quantification and adversely affect both precision and accuracy. To address this, sample dilution is an effective mitigation approach. In this study, matrix effects of 245 compounds (pesticides and metabolites) were evaluated across six representative vegetable matrices: garlic, onion, chives, perilla leaf, cucumber, and tomato, under various dilution factors. Results showed that increasing the dilution factor consistently reduced matrix effects in most matrices. For instance, high-effect matrices like garlic and onion, a 10-fold dilution approximately doubled the number of compounds within the "weak" matrix effect range. In contrast, perilla leaves and chives, which had moderate matrix effects, required two-fold and five-fold dilutions, respectively, to eliminate compounds in the "strong" effect range. On the other hand, cucumbers and tomatoes exhibited minimal matrix effects, as over 95% of their compounds were already in the weak range before dilution, so further dilution had a limited impact. Overall, these results demonstrated that dilution substantially reduced matrix effects, particularly in complex matrices. Specifically, optimal dilution factors of tenfold for garlic, onion, perilla leaf, and chives, and five-fold for cucumber and tomato, enabled accurate quantification using solvent-based calibration curves. In cases where matrix effects could not be reduced, the use of stable isotope-labeled internal standards or other matrix mitigation strategies can serve as an effective alternative.