We experienced a pufferfish poisoning case where no food residue was available to detect a causative agent. However, tetrodotoxin (TTX) was detected in vomit and urine samples from a patient using LC-MS/MS. Furthermore, we found a significant matrix effect in this analysis, indicating that the retention time of vomit and urine was not identical to the TTX standard solution and measured values multiplied by the dilution factors were not constant. Elimination of this matrix effect was attained by dilution of samples based on the retention time of the TTX standard solution, i.e., 10-time dilution of vomit test sample for LC-MS/MS analysis or 100-200-time dilution of urine one. Further research on urine analytical methods revealed that when TTX concentrations were too low to identify its peak on a chromatogram, TTX could be identified through a dilution procedure. It also showed that the application of the matrix-added TTX standard solution was effective for quantitative analysis under the influence of the matrix.
Keywords: LC-MS/MS; pufferfish; tetrodotoxin; urine; vomit.