Ionspray Tandem Mass Spectrometry for Sensitive, Rapid Determination of Minor Toxic Sesquiterpenoids in the Presence of Major Analogues of the Foreign Green Seaweed Caulerpa Taxifolia, Invading the Northwestern Mediterranean

A rapid and sensitive ionspray-ionization tandem MS method is presented for the determination of the toxic minor metabolites 10,11-epoxycaulerpenyne and caulerpenynol in the presence of the major metabolite, caulerpenyne, of the alien green seaweed Caulerpa taxifolia which is spreading in the northwestern Mediterranean. This method (a) showed no interference by any other metabolite or putative biogenetic intermediate of this seaweed, (b) needed HPLC injection merely in order to eliminate inorganic salts, (c) allowed determination of the three above compounds at the 50 mg l21 level no matter how large the excess of caulerpenyne, while being able to deal with the least amount of material compatible with handling, (d) revealed that also Indo-Pacific C. taxifolia contains all three key terpenoids above, albeit in lower amounts than the Mediterranean strain and (e) showed that none of these sesquiterpenoids was present at the above level of sensitivity in aquarium waters where the latter was growing.