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.