Development of a UHPLC-MS/MS method for the measurement of chlortetracycline degradation in swine manure.
Chlortetracycline (CTC) is a broad spectrum antibiotic, licensed for use without any withdrawal period, in chickens laying eggs intended for human consumption. In the European Union, a maximum residue limit (MRL) in eggs of 200 microgram/kg for the sum of the concentrations of CTC and its 4-epimer (4-epi-CTC) has been established. Two major CTC metabolites have been identified in eggs. These compounds, iso-CTC and 4-epi-iso-CTC, have never previously been shown to be significant products of CTC metabolism in poultry or in any other species. The total amount of CTC present in eggs, as all of the chemical forms measured, can exceed the MRL by anything up to a factor of four (170-820 micrograms/kg).