Determination of avermectin and milbemycin residues in bovine muscle by liquid chromatography-tandem mass spectrometry and fluorescence detection using solvent extraction and low temperature cleanup

A simple and inexpensive sample preparation method based on solvent extraction, followed by low temperature cleanup, was demonstrated to be applicable for the determination of avermectin and milbemycin residues in bovine muscle by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and liquid chromatography with fluorescence (LC-FL) detection. The analytical methodology was validated according to the Commission Decision 2002/657/EC, using LC-MS/MS for confirmatory and LC-FL for quantitative purposes. Mean recovery was between 88.9 and 100.7% in three distinct concentrations. The coefficient of variation for repeatability and within-laboratory reproducibility ranged from 0.78 to 5.1% and from 0.28 to 9.0%, respectively. Method precision led to satisfactory values of decision limits (CCα) and detection capabilities (CCβ). The proposed method has been applied in the Brazilian National Residue Control Plan since 2010 for the determination of avermectins and milbemycin residues in bovine muscle samples. A total of 760 samples were analyzed and none of them presented residues at concentrations above the permitted levels established by the more recently applied directives.