Optimization by Central Composite Design of a Modified QuEChERS Method for Extraction of Pesticide Multiresidue in Sweet Pepper and Analysis by Ultra-High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Abstract

With the increase of improper use of pesticides in recent years, monitoring programs for pesticide residues have become commonplace around the world. In Brazil, sweet pepper has presented the highest percentage of irregular samples over 10 years of monitoring. The aim of this study was to optimize and validate a quick and effective method for the determination of 81 pesticides in sweet pepper using modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method and ultra high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Experimental conditions of sample preparation were optimized by central composite design (CCD) in order to obtain an adequate extraction of the selected compounds. Recoveries from spiked samples at 10, 50, and 100 μg kg−1 ranged between 70 and 120 % with relative standard deviation (RSD) <20 %, except for thiophanate methyl that presented lower recoveries due degradation. Considering the occurrence of matrix effect, the quantification was performed using matrix-matched calibration. The experimental method limits of detection and quantification were 3 or 7.5 and 10 or 25 μg kg−1, respectively. In the analysis of 20 commercial samples of sweet pepper, residues of 14 pesticides were quantified in concentrations ranging from 10 to 294 μg kg−1, some higher than the MRL established by the Brazilian and European legislation. The proposed method combines the advantages of QuEChERS and UHPLC-MS/MS and proved to be suitable for the pesticide multiresidue determination in sweet pepper in routine laboratory analyses.