RESUMO
A liquid chromatographic/tandem mass spectrometric (LC/MS/MS) method was developed for determining dihydrostreptomycin, gentamicin C1, and neomycin in veal kidney, liver, and muscle. The extraction prior to injection on the automated cleanup/analysis system is very simple, permitting preparation of 24 veal samples for analysis in half a day of work. The extracts are purified online on a reversed-phase column, with the help of an ion-pairing agent, and the analytes are separated on a Nucleosil C18 column prior to analyses by electrospray MS/MS. The cleanup is sufficient to minimize ion suppression/enhancement phenomena and permits quantification of the analytes extracted from veal tissues. Four secondary ions were measured for every analyte, which gives unambiguous identification of the compounds under analysis. Calibration curves were linear for all analytes between 50 and 5000 ppb, and recoveries in kidney were 76, 57, and 51%, respectively, for dihydrostreptomycin, gentamicin C1, and neomycin. Estimated limits of detection for kidney were, respectively, 0.1, 0.1, and 0.4 ppb. When compared to an LC method with fluorescence detection, the method gave equivalent results for kidneys incurred with neomycin. This rugged method has been applied to the analysis of more than 1000 veal samples over a 1-year period.