Multi-component analysis of tetracyclines, sulfonamides and tylosin in swine manure by liquid chromatography–tandem mass spectrometry
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A multi-component method focussing on thorough sample preparation has been developed for simultaneous analysis of swine manure for three classes of antibiotic—tetracyclines, sulfonamides, and tylosin. Liquid manure was initially freeze-dried and homogenised by pulverization before extraction by pressurised liquid extraction. The extraction was performed at 75°C and 2,500 psig in three steps using two cycles with 0.2 mol L−1 citric acid buffer (pH 4.7) and one cycle with a mixture of 80% methanol with 0.2 mol L−1 citric acid (pH 3). After liquid–liquid extraction with heptane to remove lipids, the pH of the manure was adjusted to 3 with formic acid and the sample was vacuum-filtered through 0.6 μm glass-fibre filters. Finally the samples were pre-concentrated by tandem SPE (SAX-HLB). Recoveries were determined for manure samples spiked at three concentrations (50–5,000 μg kg−1 dry matter); quantification was achieved by matrix-matched calibration. Recoveries were >70% except for oxytetracycline (42–54%), sulfadiazine (59–73%), and tylosin (9–35%) and did not vary with concentration or from day-to-day. Limits of quantification (LOQ) for all compounds, determined as a signal-to-noise ratio of 10, were in the range 10–100 μg kg−1 dry matter. The suitability of the method was assessed by analysis of swine manure samples from six different pig-production sites, e.g. finishing pigs, sows, or mixed production. Residues of antibiotics were detected in all samples. The largest amounts were found for tetracyclines (up to 30 mg kg−1 dry matter for the sum of CTC and ECTC). Sulfonamides were detected at concentrations up to 2 mg kg−1 dry matter (SDZ); tylosin was not detected in any samples.
KeywordsTetracyclines Sulfonamides Tylosin Manure LC–ESI-MS–MS
Mette and Anders Lundsgaard, Niels Sørensen and Niels Jacobsen are all gratefully acknowledged for providing manure samples. This study was partly funded by grants from the European Union (ERApharm, project no. 511135) and from the Danish Directorate for Food, Fisheries and Agri Business (project no. 3401-65-03-45).
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