Screening method for tetrodotoxin using immunochromatographic test kit

The validity of an immunochromatographic test kit for tetrodotoxin (TTX) was examined. In the tests using the TTX certified standard, a strong negative correlation (r=−0.9658) was observed between the logarithm of TTX concentration and the intensity ratio of C- and T-lines (T/C) formed on the test plate in the final TTX concentration range of 0.0125-0.2 mouse unit (MU)/mL. When the intensity of the T-line was visually determined on a 5-level scale (++ > + > w+ > vw+ > −), with ++ and +(T/C > 0.4) as TTX negative and w+, vw+, and −(T/C < 0.4) as TTX positive, the presence/absence of TTX could be judged with a final concentration of ～0.06 MU/mL as the detection limit. Matrix effects were examined using non-toxic cultured pufferfish tissues, indicating that ultrafiltration and/or 5-fold dilution can reduce the matrix-induced decrease in T/C to a low level. A comparison of liquid chromatography-tandem mass spectrometry and TTX detection kit results using the toxic wild pufferfish livers showed that the kit produced false positives by about 20％, but no false negatives were observed at all. In conclusion, this TTX test kit is useful as a primary screening method for TTX.