LAUSR

In this work, a highly sensitive quantitative/confirmatory method was developed for the selective determination of marker residue 22,23-dihydroavermectin B1a in fat, kidney, liver and muscle bovine tissues using UHPLC-MS/MS. A QuEChERS method and a subsequent d-SPE cleaning with MgSO4 and C18 were used for samples preparation. The method was validated at three levels in each tissue (8.0, 20.0 and 80.0μg/kg for fat, kidney and muscle, 8.0, 16.0 and 40.0μg/kg for liver), taking into account international guidelines. Linearity and matrix effect, accuracy, within-laboratory repeatability, specificity, LOQ, LOD, Q/q relative ion intensities and uncertainty were reported. Recoveries were obtained in the range of 70-120% with within-laboratory repeatability less than 20% for the overall working range. LODs varied from 0.05 to 0.12μg/kg. Compound identification was performed using the relative intensities of monitored transitions. The method could be applied to monitoring withdrawal period specified for ivermectin in cattle.