Influence of injection solvent and serial dilution on matrix effect in GC–MS/MS multiresidue pesticide analysis: a factorial study across seven herbal matrices

Abstract Matrix effects (MEs) remain a major challenge in gas chromatography–tandem mass spectrometry (GC–MS/MS) analysis of pesticide residues, often leading to inaccurate quantification and reduced method robustness. In this study, the impact of injection solvent composition and dilution on ME was systematically evaluated for 219 pesticide residues across seven complex herbal matrices (dry mint, chamomile, green coffee, fennel, hibiscus, lemongrass, and thyme) using a factorial design approach. Two injection solvents, ethyl acetate (EA) and hexane–acetone (9:1, v/v; HA), were compared in terms of their ability to minimize signal suppression and enhancement effects. Results revealed that solvent polarity plays a critical role in determining the extent and direction of ME. When EA was used, 60% of the pesticides fell outside the negligible ME range (80–120%), showing a strong enhancement effect (53%). In contrast, HA substantially reduced ME, with only 30% of pesticides affected. Across individual matrices, dilution had variable effects: in most cases (e.g., chamomile, dry mint, fennel), dilution decreased suppression but intensified enhancement, while in pigment-rich matrices such as hibiscus and thyme, suppression became dominant. This study provides practical insights into optimizing injection solvent selection and dilution strategies to control matrix effects in GC–MS/MS analysis. The findings highlight hexane–acetone as a more reliable injection solvent for multi-residue pesticide analysis in complex herbal matrices and underscore the necessity of matrix-specific optimization to ensure accurate and reproducible results. These outcomes contribute to improving analytical method performance and reliability in food safety and regulatory monitoring.