The first identification of the rare cyanobacterial toxin, homoanatoxin-a, in Ireland

The first identification of the rare cyanobacterial neurotoxin, homoanatoxin-a, in Ireland is reported. A sensitive fluorimetric liquid chromatographic (LC) method was applied to the analysis of homoanatoxin-a in the low mug/l range. The analysis of the anatoxins in water samples required weak cation exchange solid phase extraction, fluorimetric derivatisation with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), and isocratic reversed-phase LC. Confirmation of toxin identity was made using LC with electrospray mass spectrometry (MS) of the NBD-derivatised homoanatoxin-a as well as LC-MS/MS of the free toxin. Application of the fluorimetric LC protocol to examine cyanotoxins in 20 Irish lakes resulted in the detection of homoanatoxina at four locations, Lough Sillan (24 mug/l), Inniscarra Reservoir (34 mug/l), Lough Key (12 mug/l), Caragh Lake (1.4 mug/l). An improved procedure for the isolation of homoanatoxin-a from cyanobacteria was also developed and confirmation of homoanatoxin-a was achieved by chromatographic and mass spectral comparison with authentic toxin isolated from a laboratory clone culture of Planktothrix (formerly Oscillatoria) formosa. (C) 2003 Elsevier Science Ltd. All rights reserved.