Simple confirmatory method for the determination of erythromycin residues in trout: A fast liquid-liquid extraction followed by liquid chromatography-tandem mass spectrometry

In recent years, erythromycin has received considerable attention for its therapeutic efficacy against some bacterial kidney diseases in aquaculture and, therefore, suitable and sensitive analytical methods to monitor erythromycin residues in fish are required. A fast sample treatment followed by an LC-ESI-MS/MS method is described for the purification, identification, and quantification of erythromycin A residues in fish. After two extractions with acetonitrile, samples were defatted with n-hexane, filtered, and analyzed by tandem mass spectrometry. Three characteristic transition reactions (m/z 734 -> 716, 734 -> 576, and 734 -> 558) in multiple reaction monitoring were tested for the determination and confirmation of erythromycin A. The method was in-house validated through the determination of precision, accuracy, specificity, stability, calibration curve, decision limit (CC alpha), and detection capability (CC), in accordance with European Commission Decision 657/2002. The coefficients of variation ranged from 1.8 to 9.4% and from 7.5 to 10.9% for intra- and interday repeatability, respectively. Recovery data were also satisfactory, with values varying from 85 to 97%. The method was specific, stable, and robust enough for the required purposes. The calibration curve showed a good linearity in the whole range of the tested concentrations (0-1000 mu g kg(-1)) with a correlation coefficient (r(2)) equal to 0.9956. CC alpha and CC beta were found to be 220 and 238 mu g kg(-1), respectively.