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2B - Natural Stressors and Toxicants (TUP/70) Mass spectrometric methods for the determination of anatoxins and their degradation products from cyanobacteria. Janet, Crowley1, Diaz Sierra, Monica 1, Furey, Ambrose1, Hamilton, Brett1, Lehane, Mary1, James, Kevin1, 1 Cork Institute of Technology, Cork, Ireland, Ireland ABSTRACT- Anatoxins are neurotoxins that are produced by several cyanobacteria. Anatoxin-a and homoanatoxin-a readily degrade in natural conditions, sunlight and elevated pH, to dihydro- and epoxy- analogues. Analytical studies of anatoxins in freshwaters, contaminated by cyanobacterial blooms, that use liquid chromatography with ultra-violet detection (LC-UV), fail to detect these degradation products. Derivatisation of the six anatoxins is readily achieved with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) and this has led to the development of sensitive analytical methods for the determination of anatoxins using fluorimetric detection (LC-FLD). However, LC coupled to mass spectrometry (MS) allowed the rapid and sensitive determination of the anatoxins with minimal sample clean-up. This was achieved using multiple tandem ion-trap mass spectrometry (MSn) on free and derivatised anatoxins. Sensitivity enhancement was observed in MSn modes due to high selectively and an improved signal-to-noise. A study of the mass spectra of anatoxins revealed completely different fragmentation pathways in anatoxins and their dihydro and epoxy analogues. Structural assignments of fragments were confirmed with the high mass accuracy achieved using orthogonal hybrid quadrupole time-of-flight (QqTOF) MS. These analytical methods were applied to the determination of anatoxins in cyanobacteria and freshwater samples collected throughout Ireland. Key words: QqTOF MS, ion-trap MS, neurotoxins |
