Determination of Niclosamide (Bayer 2353) in Water and Sediment Samples

A method is described for the determination of niclosamide (2′,5-dichloro-4′-nitrosalicylanilide) in river water and sediment. River water is extracted by shaking with ethyl acetate. Sediment is shaken with methanol: water (4:I), the mixture is centrifuged and the methanol is evaporated. The sediment extract is then partitioned with methylene chloride and the extracts are cleaned up on a Florisil column. Niclosamide can be analysed, after methylation with methyl iodide, by gas chromatography with electron-capture or alkali-flame detection, or directly by high pressure liquid chromatography with a UV absorbance (313 nm) detector. Recoveries of niclosamide ranged from 99 to 116% in fortified river water and 73 to 126% in fortified pond sediment samples.