Optimization and Validation of a Multiresidue Pesticide Method in Rice and Wheat Flour by Modified QuEChERS and GC–MS/MS

Abstract

An adaptation of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, using ethyl acetate instead of acetonitrile, has been proposed to extract around 100 pesticides in rice and wheat flour. This sensitive and reliable method is based on the use of gas chromatography–tandem mass spectrometry (GC–MS/MS). The method has been validated according to the European Union SANCO/12571/2013 guidelines and ISO 17025:2005. The extraction required a prior water addition, an ethyl acetate extraction of the sample, and a final cleanup step. Calibration curves were linear from 0.003 to 0.150 mg kg⁻¹ for most compounds. The limit of quantification was set at 0.0036 mg kg⁻¹ for more than 80 % of the pesticides. Recoveries were calculated at 0.004 and 0.040 mg kg⁻¹, resulting always in the range 70–116 %, and with precision values ≤20 %. The expanded uncertainty was estimated at the two abovementioned concentrations, being always ≤50 %. The method applicability has been evaluated by the analysis of real samples, and no pesticides were detected above the limit of quantification, although some minor amounts of pesticides were detected (pirimiphos methyl, tebuconazole, chlorpyrifos, and chlorpyrifos methyl) in some of them.