Mass spectral characteristics of okadaic acid and simple derivatives

Electron ionization (EI), chemical ionization (CI) and fast‐atom bombardment (FAB) mass spectra of the marine toxin okadaic acid and its syntheticf methyi, pentafurobenzyl, and trimethylislyl ester and ether derivatives were generated. Several ionization conditions and‐processing methods were used to obtain positive‐ and negative‐ion conventional spectra and tandem (MS/MS) spectra. The EF and the positive‐ion CI spectra provided fragment ions characteristic of the structure, and the negative‐ion CI and FAB spectra provided molecular ions. The addition of alkali salts to the FAB matrix resulted in reduced fragmentation and the formation of intense alkali‐metal‐cationized molecules. Pentafluorbenzyle ester derivatives provided intense carboxylate ions under electron‐captute ionization. Analytically useful MS/MS spectra obtained by low‐energy collision‐induced decomposition of the carboxylate anion produced from the tetrasilylated pentafluorobenzylokadaate.