A fast and sensitive method using high performance liquid chromatography-fluorescence detection (HPLC-FD) and ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was developed and validated for the determination of avermectins residues in ovine muscle samples. QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation based on acetonitrile extraction followed by partitioning with NaCl and Na 2 SO 4 and dispersive solid-phase extraction (d-SPE) clean-up with C18 was applied. Na 2 SO 4 was used instead of MgSO 4 due to lower amounts of co-extractives in the final extract. The procedure was validated according to the Commission Decision 2002/657/EC. The method showed determination coefficients (r 2 ) higher than 0.99, recoveries between 93.2 and 124.3% for spike levels between 0.5 and 2.0 times the maximum residues limit (MRL) values. The repeatability and intermediate precision RSD values ranged from 1 to 19%. Decision limits (CCα) and detection capabilities (CCβ) ranged from 10.7 to 59.4 μg kg -1 and 11.4 to 68.8 μg kg -1 , respectively. Method performance was successfully evaluated by analyzing real samples and proficiency test with a z-score in the range of ±1.
Keywords: veterinary drugs residue, liquid chromatography, animal tissue
IntroductionThe macrocyclic lactones (ML) are an important veterinary drug class, which are extremely effective against endo and ectoparasites.1 These compounds are structurally divided in avermectins (ivermectin, abamectin, doramectin, eprinomectin, emamectin and selamectin) and milbemycins (milbemycin oxime, moxidectin and nemadectin).2 Avermectins are the most widely applied anti-parasitic drugs in livestock, used for treatment of diseases and prevention.3 Nowadays, Brazil is a worldwide important meat producer and exporter. 4 In accordance with SINDAN, 5 avermectins represent more than 40% of all commercialized anti-parasitic drugs.To ensure that produced meat are in accordance with food safety and quality criteria required by national and international regulations, an important tool to monitor and assure this compliance is the National Residue and Contaminants Control Plan (PNCRC). 6 However, in the last years Brazilian beef products received international border restrictions due to presence of ivermectin residues above maximum residue limit (MRL) established in 10 μg kg -1 . 7 In the PNCRC, special attention is devoted to control residues and contaminants in cattle, swine and chicken. The exportation of these commodities in 2013 represented more than U$ 15.9 billion dollars. The ovine production is an important meat source in the Brazilians northeast and southern regions. This commodity provides meat, milk and wool. Currently, Brazil has around 17.6 million ovine animals, furthermore, ovine meat produced in Brazil are not included in the matrices analyzed in the PNCRC and no information about the presence of residues and contaminants is available for ovine meat. In the literature, He et al. 9 describe a method for analysis of...