A combined QuEChERS extraction/preconcentration methodology for the precise determination of pesticides in wastewater and sludge matrices.

In this study, an analytical methodology for the determination of pesticides commonly found in sludge and wastewater was developed and validated based on the citrate-buffered QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) extraction procedure. More specifically, to achieve a limit of quantification of 0.001 mg/L in a matrix of synthetic wastewater or sludge, a 1:8 preconcentration was used with the utilization of a rotary evaporator. The method was tested for twelve pesticides identified and quantified via liquid chromatography tandem mass spectrometry (LC/MS-MS) and validated according to the quality control guidelines of the EU SANTE 11312/2021. Obtained measurements provided acceptable linearity, selectivity, sensitivity, precision and accuracy at very low concentrations, indicating the potential of the method to study the fate of pesticides in wastewater and sludge samples, especially those related with fruit processing industry wastes. Recoveries at two fortification levels (0.001 and 0.125 mg/L) ranged 72-107% for the vast majority of the target analytes, with relative standard deviations of less than 20% for all analytes except one. The effect of matrix was found to be different for the wastewater and sludge with a higher ion suppression response identified for the sludge samples.