Residue depletion and risk assessment of niclosamide in three species of freshwater fish

The residue depletion of niclosamide (NIC) in freshwater fish including blunt snout bream (Megalobrama amblycephala), yellow catfish (Pelteobagrus fulvidraco) and channel catfish (Ietalurus Punetaus) were investigated under laboratory conditions. NIC concentrations in fish were determined by Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) with heated electrospray ionisation. The mean recoveries were in the range of 75.5–98.5%, with relative standard deviations ranging from 1.0 to 9.4%. The depletion results showed that the long half-life of NIC was 8.8–22.1 days. Risk assessment of NIC residue in edible tissues (muscle and skin) of the three species of freshwater fish was performed using the quotient (RQ), because of no maximum residue limit (MRL) has been set for NIC in fish. The results demonstrated that the RQ values were all significantly lower than 1. Therefore, the effect of NIC residues in the three species of freshwater fish at the immersion concentration was negligible to Chinese people.