title: [Study on preservation of niclosamide in water samples].
abstract: OBJECTIVE
  To investigate the preservation condition of niclosamide in water samples and establish a high performance liquid chromatography (HPLC) method by solid-phase extraction (SPE) which is used for determination and preservation of niclosamide in water samples.
  
  
  METHODS
  Under the simulated setting in laboratory, niclosamide was formulated into the solutions of 0.50, 1.00 mg/L and 2.00 mg/L with fishpond water. The solutions were preserved at 25, 4, -40 degrees C and -40 degrees C (repeated freezing and thawing), respectively, or 0.2% acetic acid and twice volume of acetonitrile were added into the water samples, and then the solutions were passed through the activated column, and stored at room temperature, 16 days later, the column was washed, dried and re-dissolved, and niclosamide was determined by using the HPLC method.
  
  
  RESULTS
  The concentration of niclosamide in water samples decreased at 25 degrees C or 4 degrees C, and did not change at -40 degrees C, but decreased after repeated freezing and thawing. No decrease of niclosamide was found in water samples for 16 days by using SPE. The recovery rate of HPLC was 98.12%-100.06% and the relative standard deviation (RSD) was less than 5%.
  
  
  CONCLUSIONS
  The preservation of niclosamide in water samples is frozen and protected from light without repeated freezing and thawing. The SPE method does not need to be protected from light and freezing, which can simply and effectively purify, concentrate and store niclosamide in water samples.
authors.affiliation: Jiangsu Institute of Parasitic Diseases, Key Laboratory on Technology for Parasitic Disease Prevention and Control, Ministry of Health, Center for Pesticide Effect Evaluation, Wuxi, China.
authors.forename: Yun-Tian
authors.initials: YT
authors.lastname: Xing
authors.forename: You-Zi
authors.initials: YZ
authors.lastname: Li
authors.forename: Hong-Jun
authors.initials: HJ
authors.lastname: Li
authors.forename: Guo-Li
authors.initials: GL
authors.lastname: Qu
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Jian-Ying
authors.initials: JY
authors.lastname: Wei
authors.forename: You-Sheng
authors.initials: YS
authors.lastname: Liang
authors.forename: Jian-Rong
authors.initials: JR
authors.lastname: Dai
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D008975:Molluscacides / Q000737:chemistry*; D009534:Niclosamide / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D008975:Molluscacides; D014874:Water Pollutants, Chemical; D009534:Niclosamide