Furazolidone and Nitrofurazone Metabolic Studies in Crucian Carp by Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry.

In this work, the detection of the furazolidone (FZD) and nitrofurazone (NFZ) metabolites residuals in crucian carp are focused. Crucian carps of identical size were exposed to the mixed nitrofuran antibiotics under optimized bath conditions at a concentration of 50 mg/L, 26 ± 0.5°C for 24 h. Then, liquid chromatography-electrospray ionization-triple quadrupole mass spectrometry (LC-ESI-MSMS) was performed after the drug exposure experiments when the nitrofuran metabolites were enriched in organisms. During the period of 0-144 h, residue levels of the 3-amino-2-oxazolidinone (AOZ) gradually decreased with a prolonged sampling time. The changing trend in semicarbazide (SEM) with the sample collection duration is divided into two stages, and its concentration showed a trend of rising first and then falling. The metabolite concentration-time curve demonstrates that 24 h was used as a sampling time, and fish muscle was selected as tissue samples in the further quantitative study. A novel crucian carp-enrichment procedure coupled to LC-ESI-MSMS quantitative method was further explored based on much metabolite data. According to the exponential curve of the SEM-to-AOZ concentration ratio at a precisely designed FZD-to-NFZ mass ratio, the final FZD content of the veterinary NFZ antibiotics was 0.069 ± 0.005% (in terms of mass).