Residues of coccidiostats in eggs of German origin and studies on the degradation behaviour of coccidiostats under different conditions

Coccidiostats are used, especially in poultry, against coccidiosis, a disease caused by the intestinal protozoa "Eimeria". These drugs should not be administered to laying hens in order to prevent residues in eggs. However, coccidiostats are applied for rearing of broilers. In compliance with feed-legal norms and appropriate waiting times it should be ensured that residues of coccidiostats are not occurring in eggs. However, available literature data show that residues of coccidiostats in eggs are quite often found at detectable levels. The objective was to improve an existing method for the simultaneous isolation and analysis of active substances like diclazuril, lasalocid, narasin, nicarbazin and salinomycin from the egg matrix. Furthermore, the degradation behaviour of these substances should be measured by "in vitro" - and "in vivo" - studies under various conditions of the medium and initial investigations on the detection of degradation products were performed. For the measurement an improved LC-MS/MS method was applied. Introducing a further extraction step and reducing the evaporation temperature of the samples, it was possible to improve the recovery of the already existing method. Investigating the degradation behaviour of the substances in aqueous solution and in the egg under different temperature- and pH-conditions, coccidiostats proved to be relatively stable substances even over a period of five weeks. For the coccidiostat salinomycin two metabolites could be detected. An oxygen adduct and an isomer which reveals the same mass as the starting material. However, the chromatogram shows a different retention behaviour and does not provide the same fragmentation daughter ions as the starting substance salinomycin. A definite characterization of these newly analysed metabolites is still pending