Method validation and evaluation of household processing on reduction of pesticide residues in tomato

Metalaxyl and chlorpyriphos are widely used pesticides around the world. The purpose of this study was to evaluate validation parameters, matrix effect (ME %), reduction behavior, processing factor (PF) and estimate the behavior of metalaxyl and chlorpyriphos in tomato fruit samples. "Quick, Easy, Cheap, Effective, Rugged, and Safe" (QuEChERS) extraction and gas chromatography coupled to mass spectrometry (GC/MS) were used for the analysis. Results showed successful trends by evaluating validation parameters [selectivity, linearity, limits of detection (LOD), limits of quantification (LOQ) and precision]. The correlation coefficients were > 0.99; the LOD for metalaxyl ranged from 0.01 to 0.003 mg/kg and the LOQ for chlorpyriphos ranged from 0.03 to 0.009 mg/kg. The matrix effect (ME %) of metalaxyl was found to exhibit a medium matrix effect while for chlorpyriphos no matrix effect was seen. Recovery (70-120%) and precision (RSD < 20%) for both pesticides metalaxyl and chlorpyriphos were within the satisfactory ranges recommended by the European Commission. The PF was generally < 1 (ranged between 0.34 and 0.98). Except when using washing solutions, metalaxyl PFs were > 1. The highest reduction rate was achieved by sonication treatments which could effectively remove chlorpyriphos residues spiked in tomato matrices rather than the metalaxyl residues. On the other hand, washing treatments were less efficient in removing metalaxyl residues from tomato samples. Overall, any one of these processes can contribute substantially to reduce consumer exposure to pesticides residues in tomatoes.