Liquid chromatography/quadrupole time-of-flight mass spectrometry for determination of saxitoxin and decarbamoylsaxitoxin in shellfish

Saxitoxin (STX) and decarbamoylsaxitoxin (dcSTX) were determined by liquid chromatography with quadrupole time-of-flight mass spectrometry (Q-TOF MS). A shellfish tissue was extracted with 0.1 mol/l HCl under ultrasonication, and cleanup of extract was accomplished by solid-phase extraction with a C18 cartridge. Chromatographic separation was carried out on a C18 column (150 mm x 2.1 mm, 3.5 microm) with gradient elution of MeOH-H2O (20:80) containing 0.05% heptafluorobutyric acid and MeOH-H2O (15:85) containing 0.05% acetic acid. The protonated molecule M + H]+ ions at m/z 257 for dcSTX and 300 for STX were selected in precursor ion scanning for Q-TOF MS in the positive electrospray ionizaion mode. Average recoveries and relative standard deviations, by analyzing samples spiked at a level of 0.1, 0.8 or 1.6 microg/g, were 84-92 and 8-14%, respectively. Identification of the presence of the toxins in shellfish tissues was based on the structural information offered by Q-TOF MS.