Determination of pectenotoxin-2 after solid-phase extraction from seawater and from the dinoflagellate Dinophysis fortii by liquid chromatography with electrospray mass spectrometry and ultraviolet detection : Evidence of oxidation of pectenotoxin-2 to pectenotoxin-6 in scallops

Abstract

Solid-phase extraction of pectenotoxin-2 (PTX2) and pectenotoxin-6 (PTX6) from seawater samples using a nonpolar cartridge column Sep-Pak C 18 was investigated for determination of PTXs in toxic phytoplankton. PTX2 and PTX6 were almost completely recovered from the seawater samples. Determinations of PTX2 from the toxic phytoplankton and scallops were carried out by liquid chromatography (LC) on UV trace equipped with an atmospheric pressure electrospray ionization mass spectrometry (ESI-MS). PTX2 obtained from the toxic phytoplankton and scallops yielded a mass spectra exhibiting abundant [M+H] +, [M+NH 4] + and [M+Na] + indicating that ESI-MS is useful for the identification of PTX2. Determinations of PTX6 from the toxic phytoplankton and scallops were carried out by LC fluorescence detection. A significantly higher content of PTX6 compared to PTX2 in scallops was observed, suggesting that a transformation of PTX2 to PTX6 in tissues of the scallops occurs rapidly.