Analysis of dissipation and transformation products of oxytetracycline by HPLC- MSn

IVANIC, FEDERICO; CANDAL, ROBERTO J.; BUTLER, MATIAS

San Diego

Conferencia; Pittcon 2024; 2024

The Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy

The frequent use of the broad spectrum antibiotic oxytetracycline (OTC) in areas of intense animal husbandry represent a harmful threat to the ecosystems and human health. The sediment phase has a major influence on the distribution and fate of this contaminant also affecting its degradation. Lab experiments simulating the conditions of water-sediment systems assist in the study of the dissipation and transformation products (TPs) of the contaminants whereby tandem mass spectrometry facilitates the detection and characterization of low abundance products in complex matrices. Batch degradation experiments of OTC were carried out in reactors containing water and artificial sediments inoculated with a microbial consortium under non-aerated conditions. Samples from the aqueous and the sediment phases were withdrawn periodically and prepared accordingly for their analysis by HPLC-MS n . Multiple tandem mass spectra were acquired using a linear ion trap mass spectrometer (Thermo LTQ XL) with an electrospray source in positive-ion mode. The search of TPs was achieved by a non-targeted screening approach, using MatLab software to filter potential candidates. Fragmentation pathways were analyzed to propose chemical structures for the most abundant products. Identified TPs were later searched in environmental samples of water and sediment withdrawn from a stream near a livestock establishment.Concentration of OTC in solution was lower than 3% after 10 days whereas the percentage in sediment was close to 30%, and about 6% of the initial concentration after 45 days. Besides OTC, many of its TPs were also adsorbed and accumulated in the sediment. Throughout 45 days, the temporal evolution of nearly 60 TPs could be characterized upon desorption from the sediment in contrast to 30 TPs from solution. At least 15 of these TPs could also be detected in the environmental samples, highlighting the significance of the methodology employed for environmental analysis and contaminant monitoring.