Use of Factorial Design in the Development of Multiresidue Method for Determination of Pesticide Residues in Wheat by Liquid Chromatography-Tandem Mass Spectrometry

The evaluation of analytical methods for determining the level of residues and contaminants in food samples is a continuing need. To improve this evaluation, it is necessary to investigate different extraction procedures and conditions. A 2³ factorial design was applied to establish an analytical method for determining pesticide residues in wheat by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Factors that influence the recovery of compounds, such as agitation and different processes of partition and cleanup, were investigated. Extracts were analyzed by LC-MS/MS with electrospray ionization in a triple quadrupole system. The use of ultrasonic agitation in the extraction step, deep freezing for the partition step, and C18 cleanup provided significantly better recoveries for most of the compounds evaluated. Assessment of each factor as well as interactions between factors allowed for a more effective evaluation of the parameters involved in the development of analytical methods. The validation results were satisfactory, since the method presented linearity (r ²) >0.99 for all compounds, the matrix effect ranged from 3 to 97 % and was corrected by matrix-matched standards, and recoveries ranged from 70 to 120 % with RSD ≤20 % for the spike levels of 10 and 100 μg kg^?1. The method limit of detection and limit of quantification ranged from 3.3 to 6.7 μg kg^?1 and from 10 to 20 μg kg^?1, respectively, and the expanded uncertainty ranged from 15 to 32 %. The proposed method met the criteria for determination of 42 pesticides in wheat samples and was successfully tested in real samples.