Detection of tetrodotoxin (TTX) and its analogues in mud snails Nassarius livescens occurring on a sandy beach in Jeju Island, Korea, using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

Recent studies have reported on the occurrence of tetrodotoxin (TTX), a sodium channel-blocking neurotoxin commonly found in pufferfishes, in various marine gastropods in tropical and temperate shallow marine environments, raising concern for potential seafood poisoning as the sea snails are consumed. The intertidal beaches and rocky shores of Jeju Island include numerous subtropical and temperate gastropods including mud snails, which are commonly exploited as seafood. Accordingly, surveillance of TTX-bearing gastropods in intertidal Jeju Island is necessary to ensure seafood safety. In this study, we first screened TTX in 15 gastropod species from the Jeju coast using TTX-specific competitive ELISA. The ELISA indicated that mud snail Nassarius livescens contained a certain level of TTX in their muscle and visceral mass, whereas 14 species of gastropods were free from TTX. Accordingly, the levels of TTX and its analogues were determined in 30 individuals of N. livescens using liquid chromatography–tandem mass spectrometry (LC–MS/MS). The LC–MS/MS applied in this study showed a quantification limit (method detection/quantification limit [MDL/MQL]) of 18–19 µg/kg and 56–57 µg/kg, respectively, indicating that the LC–MS/MS was sensitive enough to detect a small quantity of TTX in the tissues. The TTX levels in the muscle ranged from below the detection limit to 3006.9 µg/kg, and those in the viscera ranged from below the detection limit to 1457.2 µg/kg. The detection frequency of TTX in mud snails was 83.3% in muscle and 70.0% in visceral mass, indicating that most N. livescens contained TTX. The LC–MS/MS also revealed several TTX analogues in the tissues, including epi TTX, anhydroTTX, deoxyTTX, dideoxyTTX, trideoxyTTX, and norTTX.