Standardized extraction method for paralytic shellfish toxins in phytoplankton

The optimal conditions were established for extraction of paralytic shellfish toxins from a Danish clone of Alexandrium tamarense using extraction with acetic acid and HCl in the concentration range 0.01-1.0 N. Physical destruction of the cells was investigated microscopically to select the most efficient extraction procedure. The toxin content was quantitated by an automized isocratic reversed-phase high-performance liquid chromatography (HPLC) method. The best results as judged from the total amount of toxins and the toxin profile were obtained using 0.05-1.0 N acetic acid and 0.01-0.02 N HCl. Hydrochloric acid in the concentration range 0.03-1.0 N caused the amount of C1 and C2 toxins to decrease sharply and concomitant increase of gonyautoxins 2 and 3. The phytoplankton extracts with 0.1 to 0.5 N acetic acid or 0.01 N HCl were stable during 6 months at -20 degrees C, but the extracts with HCl greater than or equal to 0.02 N underwent a change in toxin profile, although the total amount of toxins was constant.