High-performance liquid chromatographic analysis of Romet-30 in Chinook salmon ( Oncorhynchus tshawytscha): wash-out time, tissue distribution in muscle, liver and skin, and metabolism of sulfadimethoxine

Abstract

A high-performance liquid chromatographic (HPLC) assay was developed for the determination of Romet-30 residue levels in Chinook salmon muscle and liver tissues. The extraction recoveries averaged 66, 78 and 83% for ormetoprim (OMP), sulfadimethoxine (SDM) and N 4-acetyl-SDM (N 4-Ac-SDM), respectively, in muscle tissue; 61 and 72% for SDM and N 4-Ac-SDM, respectively, in liver tissue. The HPLC assay had a lower detection limit of 0.05 μg/g for OMP, SDM and N 4-Ac-SDM in muscle tissue, and a lower detection limit of 0.20 μg/g for SDM and N 4-Ac-SDM in liver tissue. OMP could not be quantified in liver due to the presence of substantial amounts of co-extracted endogenous substances. The HPLC assay was applied to the analysis of Romet-30 residues in Chinook salmon after gastric intubation with Romet-30 at water temperatures between 8.0 and 9.0°C. Different disposition characteristics were found in muscle and liver tissues. The presence of N 4-Ac-SDM in liver tissue was confirmed by MS and MS-MS analyses. An estimation of SDM and N 4- Ac-SDM residue levels in skin tissue was obtained and the disposition of these two compounds was similar to the disposition in muscle tissue.