Determination of pesticide residues in watermelons by LC-MS/MS

Abstract

The LC–MS/MS was applied for the detection of pesticide residues in watermelons. Since watermelons are predominantly used as fresh food and to a lesser extent in food processing there is a justified concern that, due to treatments, they can contain pesticide residues above the maximum residue levels – MRLs. The pesticide extraction was carried out by QuEChERS method. The samples were tested regarding the content of 55 pesticides with the carbofuran-D3 as internal standard. The linearity was studied in the range of 0.01–0.50 mg/kg and the determination coefficients (R2) were higher than 0.99 for all the investigated pesticides. The calibration was performed as matrix calibration, by means of spiking the calibration samples before the extraction and preparing them in the same way as the test samples. The recovery data were obtained by spiking blank samples at three concentration levels (0.01, 0.05 and 0.1 mg/kg) yielding recoveries in the range of 61.0–114.2% with the relative standard deviation (RSD) less than 13%. The limits of quantification (LOQs) were established as 0.01 mg/kg. The multiple detections were confirmed in the analysed samples. The most frequently detected pesticides were carbendazim, acetamiprid, tefluthrin and fenpropimorph. In only one sample the concentrations of carbendazim and tefluthrin were above the MRLs.