[Determination of Tetrodotoxin in Miso Soup byStrong Cation Exchange Solid Phase Extraction and LC-MS/MS]

A method for analyzing tetrodotoxin (TTX) in miso soup samples was proposed. The samples were purified using strong cation exchange solid-phase extraction and analyzed by liquid chromatography-tandem mass spectrometry. The recovery of TTX was considerably influenced by the salt concentration in the loading solution during purification. It was observed that diluting the loading solution to reduce the salt concentration helped to maintain the recovery rate during the washing step. However, during the loading step, the benefit of dilution in improving recovery was not evident, as the enhanced retention on the solid phase caused by dilution was counteracted by losing TTX with the increased volume of the loading solution, which led to enhanced elution. This suggests that the volume of extraction solution used in the loading process is crucial in determining the recovery rate. Additionally, the use of volatile ammonium acetate as the elution solvent was explored to optimize conditions for effective recovery. Testing this method on miso soup samples with varying miso types, salt concentrations, and TTX levels resulted in consistently high recovery rates of>80%.