Evaluation of the matrix effect of pH value and sugar content on the analysis of pesticides in tropical fruits by UPLC-MS/MS

Matrix effect (ME) is a critical factor that can significantly compromise the accuracy of pesticide residue analyses performed using ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS). In this study, five pesticides of different types, namely difenoconazole (triazoles), chlorpyrifos (organophosphates), thiram (dithiocarbamates), carbaryl (carbamates), and pyraclostrobin (strobilurins), were selected to investigate the UPLC-MS/MS MEs in five typical tropical fruits. The MEs and possible mechanisms of the main influence factors, i.e., pH value and sugar content, were studied for the pesticide residues in the tropical fruits. The proposed method was validated in terms of linearity, limit of detection (LOD), recovery, and precision. In the range of 0.005–0.5 μg mL −1 , the coefficients of determination (r) were better than 0.999, while the LODs and recoveries ranged from 0.16 to 4.4 μg kg −1 and from 75% to 120%, respectively. Results show that among the five typical tropical fruits, the ME was largest in longan, followed by that in banana; pineapple and guava showed lower MEs than those in banana, whereas papaya had the lowest. Chlorpyrifos has the largest ME, followed by thiram and difenoconazole, and the other pesticides have very small MEs. Moreover, the MEs can be reduced by adjusting the pH value and sugar content of the sample matrix. This study can be applied to assess the influence of MEs on the analysis results.