Direct analysis of microcystins by microbore liquid chromatography electrospray ionization ion-trap tandem mass spectrometry

Microcystins are a group of structurally similar cyclic heptapeptide hepato toxins and tumor promoters, produced by cyanobacteria. A microbore liquid c hromatography electrospray ionization ion-trap mass spectrometry (LC-ESI-IT MS) method has been developed which is capable of separating and detecting trace amounts of microcystin variants in environmental samples. Extracted w ater sample was loaded onto a LC trapping column and, using a column switch ing technique, the compounds of interest were back-flushed onto a 1-mm LC c olumn. Structural elucidation was achieved using ion-trap with tandem mass spectrometry in the data dependent scan mode. Collision-induced dissociatio n to MS3 allowed tentative identification of these cyclic peptides. Full-sc an LC-ESI-MS mass spectrum was obtained when 250 pg of the authentic compou nd was injected onto the HPLC column, which represents the detection limit for microcystin-LR. This study demonstrated that LC-ESI-ITMS is a reliable and sensitive technique for analysing trace levels of microcystins. (C) 200 0 Elsevier Science B.V. All rights reserved.