Determination of fluralaner residues in eggs by LC-MS/MS and laying hen withdrawal trial

The presence of residues of veterinary drugs in eggs is an ongoing and significant issue of concern. Fluralaner is widely used in the prevention of ectoparasites, including the poultry red mite, but no analytical method has been reported for detection of its residues in eggs. An HPLC-MS/MS method was established for the determination of fluralaner residues in whole eggs and validated for LOD, LOQ, specificity, linearity, accuracy, precision, and matrix effects. LOD was 5 μg•kg−1 and LOQ was 65 μg•kg−1. Recovery ranged from 97.7% to 103.7% (spiked at 65, 650, 1300, and 2600 μg•kg−1), while intra-assay and inter-assay coefficients of variation were consistently below 1.5%. A drug withdrawal trial was conducted with 16 laying hens administered a therapeutic dose of fluralaner in drinking water on days 0 and 7, with eggs being analyzed for 23 days. The highest concentration, 1235 μg•kg−1, was detected on day 13. This was below the European Union maximum residue limit for fluralaner in edible chicken tissues and eggs (1300 μg•kg−1). Residues were detectable up to two weeks after cessation of treatment. This method is suitable for routine compliance monitoring of fluralaner residues in egg matrices and may be adapted for analysis of other edible tissues.