A simple liquid chromatography coupled to quadrupole time of flight mass spectrometry method for macrolide determination in tilapia fillets

A method for the identification and quantification of macrolides (erythromycin, josamycin, tilmicosin, tylosin, spiramycin and neospiramycin) in tilapia fillets by liquid chromatography coupled to quadrupole time of flight mass (LC–QToF) spectrometry is presented. Sample preparation was quite simple and low cost: proteins were precipitated and the analytes were extracted with ethanol, extract was defatted with hexane and concentrated by solvent evaporation. The matrix effect was statistically demonstrated during method validation, in which matrix-matched calibration was applied. Matrix effect mechanism was clarified thanks to the capability of QToF mass spectrometer of generating full scan spectra with accurate mass measurement. The limits of quantification were at least 45% lower than the maximum residue limits. The method was able to identify the studied macrolides with relative m/z errors lower than 2.5 ppm and to monitor two fragment ions per analyte, which is in accordance with the European Community recommendations for the analysis of contaminants in foods. Samples from the retail market of São Paulo State, Brazil, were analyzed by the developed method and none of them presented positive results for the macrolides studied.