A modified quechers method for analysis of five pesticides residues in cow’s milk by GC-MS analysis

In this study, cow's milk samples were used to determine the presence of residues substances (amitraz, fluazuron, eprinomectin, chlorpyrifos, cypermethrin and dichlorvos). The first stage was carried out to validate the QuEChERS (modified) method of extraction and the second stage involved characterization and quantification of the residues of these chemical substances contained in cow's milk from the Unicesumar experimental farm. The methodology was validated through the analysis of average recoveries greater than 90%, excellent precision (<20%) and low detection limits (0.023 to 1.79 µg L-1) and quantification (0.05 to 3.13 µg L-1). The milk collected from groups of dairy cattle (Dutch black and white) showed high amounts of residues on days 0, 1 and 2 after application, with the highest concentration being chlorpyrifos on day 0 (632.2 µg L-1). The QuEChERS methodology combined with gas chromatography coupled with mass spectrometry proved to be an easy to apply and highly efficient method for the development of routine analyzes in the quality control of cow's milk for the detection of residues of veterinary drugs used to combat ticks in cattle dairy.