Simultaneous determination of niclosamide and its degradates in water by LC-MS/MS

A new method for the analysis of niclosamide (NIC) and its primary degradates 2-chloro-4-nitroaniline (2C4NA), aminoniclosamide (AN), hydroxyniclosamide (HN) and 5-chlorosalicylic acid (5CSA) in water was developed using direct injection LC-MS/MS. Methanol and acetonitrile mobile phases were compared. Methanol was superior for both separation and sensitivity for all chemicals. LLoQs for all chemicals were 3-50 times better in methanol than in acetonitrile, and baseline separation was observed for HN and 5CSA in methanol but not acetonitrile. The LLoQ for NIC in the current study was approximately 20 times lower than that previously reported using LC-MS/MS methodology, and 10-250 times lower for all chemicals than obtained by HPLC-UV/visible detection. The method reported in the current study relies upon smaller injection volumes and direct injection of water, eliminating time consuming clean-up steps and increasing sample throughput. The current method is also more selective for all four chemicals than existing HPLC-UV/visible methods, and is not susceptible to spectral interferences from DOM. The use of a shorter LC column with core shell particles resulted in shorter run times and lower mobile phase consumption than previously reported methods for MC, which rely on traditional porous particle columns.