Determination of 23 organochlorine pesticides in animal feeds by GC-MS/MS after QuEChERS with EMR-lipid clean-up

Abstract

A method has been developed to analyse 23 organochlorine pesticides in animal feed. These persistent pesticides include DDTs, dieldrin, and chlordane. All pesticides were subject to legislation by Commission Regulation (EC) 396/2005. The variation in the feed composition matrix was reduced by using a QuEChERS method, which included freezing with CaCl₂, based on a clean-up with Enhanced Matrix Removal—Lipid (EMR-L). The method involves two steps: screening and quantification, and has been developed and validated following the SANTE/11813/2017 criteria. The analytes were extracted and analysed by gas chromatography coupled to a triple quadrupole mass spectrometer (GC-QQQ). Separation was achieved in 22 min. Satisfactory results were obtained in the screening method validation. This was tested by evaluating the detection and identification of analytes in spiked samples in 21 different feeds. Excellent linearity and good sensitivity were achieved in the quantification method validation based on calibration by standard addition, which reduces the matrix effect. Recoveries between 70 and 120% at the quantification limit of 0.005 mg kg⁻¹ were also obtained. In Catalonia, 200 samples of various feed matrices from agriculture production were analysed with good results, obtaining only 1% positives. The main positive pesticide was DDE; its presence in the sample could be due to the persistence of this family of pesticides in the environment.