This study aimed to validate a method developed for the determination of six antibiotics from the polyether
ionophore class (lasalocid, maduramicin, monensin, narasin, salinomycin and semduramicin) at
residue levels in raw, UHT, pasteurized and powdered milk using QuEChERS extraction and high performance
liquid chromatography coupled to tandem mass spectrometry (HPLC–MS/MS). The validation was
conducted under an in-house laboratory protocol that is primarily based on 2002/657/EC Decision, but
takes in account the variability of matrix sources. Overall recoveries between 93% and 113% with relative
standard deviations up to 16% were obtained under intermediate precision conditions. CCa calculated
values did not exceed 20% the Maximum Residue Limit for monensin and 25% the Maximum Levels for
all other substances. The method showed to be simple, fast and suitable for verifying the compliance
of raw and processed milk samples regarding the limits recommended by Codex Alimentarius and those
adopted in European Community for polyether ionophores.