A method for the analysis of several macrolide and ionophore antibiotics as well as tiamulin in liquid manure was developed. Reversed-phase liquid chromatography and atmosheric pressure chemical ionisation (APCI) tandem mass spectrometry was used for detection. High-performance liquid chromatographic (HPLC) separation of the antibiotics was achieved in 35 min. The analytes were extracted with ethyl acetate and the extracts were cleaned up by solid-phase extraction on a diol SPE cartridge. Recovery experiments with spiked liquid manure concentrations varying from 6 to 2,000 μg kg~(-1) gave constant recovery rates. The recovery rates for the macrolides erythromycin, roxithromycin and oleandomycin were 75-94, that for the ionophore salinomycin was 119, while that for the pleuromutilin tiamulin was 123, when using a macrolide internal standard. The relative standard deviation was found to be 15-36 and the limits of detection were 0.4-11.0μg kg~(-1). The maximum concentrations found in manure samples were 43 μg kg~(-1) for tiamulin and 11 μg kg~(-1) for salinomycin.
展开▼
