Targeted screening and safety evaluation of 276 agrochemical residues in raisins using buffered ethyl acetate extraction and liquid chromatography–tandem mass spectrometry analysis

Abstract

A buffered ethyl acetate extraction method was optimized and validated in raisin matrix to monitor 276 pesticides by liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis. The final method involved homogenization of raisins along with water (1:1 raisins: water)followed by extraction using ethyl acetate (10 mL/10 g raisins homogenate)in presence of 0.1 mL acetic acid, 0.5 g sodium acetate and 10 g sodium sulphate, and clean up by dispersive solid phase extraction with primary secondary amine sorbent (25 mg/ 5 mL extract). 276 pesticides were estimated within 20 minutes of chromatographic run time by retention time dependent ‘scheduled multiple reaction monitoring’ (sMRM) by LC MS/MS. The method was validated as per European guideline, DG-SANTE/11945/2015, at 2, 10, and 25 ng/g spiking levels where the method precision in terms of repeatability was <15% at 10 ng/g for 93.8 % of the compounds. The Limit of quantification (LOQ) ranged between 0.01-10 ng/g with recoveries 70-120% with ≤20 % RSD for 93.5% of compounds at regulatory default MRL of 10 ng/g. The matrix induced signal suppressions or enhancement were moderate (60-130% accuracy against solvent standard) for 85% compounds in white raisins and 67% compounds in black raisins. The method was successfully applied for screening of 94 market samples of raisins for the target analytes. The dietary exposures calculated against the average concentrations detected were well below the maximum permissible intake (MPI) values and the collected raisin samples were considered safe for human consumption without any acute toxicity hazard.