ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY OF SPHINGANINE ANALOG MYCOTOXINS

The ionization and fragmentation behavior of two groups of sphinganine analog mycotoxins (SAMs), the AAL toxins (TA, TB, TC, TD, and TE) and fumonisins (FB1 and FB2), were compared in positive and negative electrospray ionization (ESI) modes. Toxins containing amino groups yielded abundant [M + H](+) in positive mode, whereas N-acetylated toxin congeners were protonated less efficiently but yielded abundant [M + Na](+) ions, Negative ESI mass spectra exhibited abundant [M - H](-) ions for all toxins, and fumonisins could be distinguished by the presence of additional peaks corresponding to [M - 2H](2-). Negative mode ionization facilitated the detection of a new AAL toxin, corresponding to N-acetylated TA, that was not evident in positive ESI mass spectra of a fungal culture filtrate. Low-energy collisional activation of deprotonated toxins yielded fragment ions characteristic of the tricarballylic acid moiety, whereas protonated toxins fragmented to give more information about the structure of the rest of the molecule. Collisional activation performed in the transport region of the electrospray source yielded fragment patterns similar to those obtained from low-energy collision activated dissociation generated in a collision cell, AAL toxins TA and TD were detected in spiked extracts of vegetable juice and fumonisin FB was detected in spiked corn extracts using positive ESI, with detection Limits ranging from 4 to 10 mu g/mL injected, Additional sample cleanup will be required for confirmation of SAM contamination of foods at sub-parts per million levels using flow injection ESI since unidentified matrix components suppressed ionization in both positive and negative modes, At present, ESI in positive or negative mode is the only analytical tool shown to be capable of detecting all SAM congeners.