A Generic Approach for Simultaneous Screening and Quantification of Aflatoxins and Pesticide Residues in Rice by LC-MS/MS: Single Laboratory Validation

BACKGROUND: Chemical residues in rice require highly sensitive analytical methods to verify compliance with stringent residue limits. In addition to pesticide residues, aflatoxins are critical contaminants due to their toxicity and carcinogenicity. OBJECTIVE: To develop and validate a simple, generic LC-MS/MS workflow for simultaneous screening and quantification of pesticide residues and aflatoxins in rice. METHODS: Samples were extracted using a modified QuEChERS EN 15662:2018 procedure with acidified acetonitrile, followed by dispersive solid-phase extraction cleanup. Analysis was performed using a UHPLC coupled to a triple quadrupole mass spectrometer (QQQ) with heated electrospray ionization in time-scheduled selected reaction monitoring mode. Method performance was assessed in accordance with SANTE guidance using matrix-matched calibration. RESULTS: The optimized LC-MS/MS method demonstrated many transitions with polarity switching while maintaining acceptable chromatographic peak quality and selectivity. Acidified extraction improved the response by 3- 5-fold for the selected analytes. The method achieved LOQs of 0.0005 mg/kg for pesticides and aflatoxins. Calibration was linear over 0.0005-0.050 mg/kg for pesticides and 0.0002-0.010 mg/kg (0.2 -10 µg/kg) for aflatoxins, with R² ≥ 0.99 and residuals within ±20%. Recoveries for all target analytes were within 70- 120%, with precision ≤20% RSD at the evaluated spike levels. CONCLUSIONS: The proposed single-extraction LC-MS/MS workflow is selective, sensitive, accurate, and suitable for the simultaneous high-throughput determination of pesticide residues and aflatoxins in rice. The method meets SANTE criteria for pesticides, complies with the Commission Implementing Regulation (EU) 2023/2782 for aflatoxins, and complies with FSSAI and EU MRLs/MLs for rice.