On-line liquid chromatography electrospray ionization mass spectrometry for determination of the brevetoxin profile in natural ''red tide'' algae blooms

Reversed-phase liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) was employed to analyze brevetoxin compounds associated with naturally occurring red tide blooms collected from Sarasota Bay, FL, USA. The LC-ESI-MS method utilizes a C-18 microbore column with a mobile phase consisting of methanol-water (85:15, v/v), a flow-rate of 8 mu l/min and a post-column split ratio of 3:1 (UV-absorbance detector-mass spectrometer). Three known brevetoxins Btx-2, Btx-1 and Btx-3 were detected at 60 mu g/l, 10 mu g/l and 5.7 mu g/l levels, respectively, in the natural red tide bloom samples. This distribution differed quantitatively from that found in red tide culture extract samples. Btx-9 was not detected either in natural red tide bloom extracts or in red tide culture extracts, possibly due to the instability of this compound. An unknown component with a molecular mass of 941 found in the natural bloom extract was postulated to have the structure of a reduced form (hydrogenation of two double bonds in the alkyl side chain) of Btx-5.