Degradation and residue dynamics of veterinary medicines in soil-plant systems

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Aim of the project is to characterize the fate of veterinary pharmaceuticals (sulfadiazine, SDZ, and difloxacin, DIF) in manure amended soil in presence of maize, i.e., the kinetics and mass balance of degradation, mineralization rates, the formation of non extractable residues (NER) by parent compounds and metabolites, the potential remobilization of NER as well as the structural elucidation of soluble and bound residues. For this purpose as well as for other partners we will synthesize various derivatives labelled with 14C- and 13C-isotopes: (1) [U-phenyl-13C]-SDZ; (2) [U-phenyl-13C]-acetyl-SDZ; (3) [U-phenyl-13C]-4-hydroxy-SDZ; (4) [2-Pyrimidyl-14C]-N-acetyl-SDZ; (5) 14C-labelled OH-SDZ. Further derivatives are available from the first part of the project cluster ([2-Pyrimidyl-14C]-SDZ and [2-13C,1-15N]-DIF) and will be provided by external synthetic laboratories (14C-labelled DIF). The parent compounds and independently the metabolites Ac-SDZ and OH-SDZ (according to one of the proposals hypothesis) will be incubated in planted soil applying spiked manure under experimental conditions as close as possible compared to the central experiment performed in Jülich. For structural investigation of the bound 13C-labelled residues high resolution NMR after sample solubilisation and CP-MAS NMR spectroscopy of solid samples will be applied.