CHARACTERIZATION OF THE OXIDATION-PRODUCTS OF PARALYTIC SHELLFISH POISONING TOXINS BY LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY

Periodate oxidation of the toxins responsible for paralytic shellfish poisoning (PSP) yields fluorescent products that are useful for trace analysis by reversed-phase liquid chromatography. Some toxins are oxid ized to the same product, while others are transformed to a mixture of products; in all cases, the products are too unstable to be isolated preparatively. A mobile phase containing heptafluorobutyric acid as an ion-pair agent was developed to improve compatibility with liquid chr omatography/mass spectrometry (LC/MS) analysis. Several LC/MS techniqu es were investigated: chemical ionization with the moving belt interfa ce, atmospheric-pressure chemical ionization, thermospray, continuous- flow fast-atom bombardment, and ion-spray. Only LC/ion-spray MS was ab le to provide spectra of the oxidized products. The products were char acterized as purines resulting from: (a) breakage of the C4-C12 bond a nd aromatization of the remaining rings (loss of 4 hydrogens); (b) par tial elimination of a carbamoyl or N-sulfocarbamoyl side-chain (this i s promoted by the presence of an N-1-hydroxy group); and (c) partial h ydrolysis of an N-sulfocarbamoyl side-chain to a carbamoyl group.