A sensitive LC–MS–MS method has been established which allows the simultaneous detection of four nitrofuran antibacterial drugs in animal muscle tissue via their metabolites. In its course, the bound analytes (metabolites) are released from tissue by acidic hydrolysis and simultaneously derivatised using 2-nitrobenzaldehyde. The introduction of an analyte-selective solid-phase extraction step greatly facilitated an efficient sample clean-up. Detection limits of the analytes ranged from 0.5 to 5 ng g−1, and linearity of the detector response was excellent between the limit of determination up to 800 ng g−1. Electrospray ionisation tandem mass spectrometry was used for detection and two fragment ions per analyte have been used as additional identifiers taking EU regulations into account.
A simple sample preparation protocol including solid-phase extraction and the addition of an internal standard has led to a sensitive and robust method. The analysis of muscle tissue samples from animals treated with furazolidone and furaltadone allowed unequivocal identification of the AOZ and AMOZ metabolites at concentrations which were expected from literature values and which were approximately two orders of magnitude above the method’s detection limit.