Reversed-phase liquid chromatographic-mass spectrometric determination of microcystin-LR in cyanobacteria blooms under alkaline conditions.

Reversed-phase HPLC coupled to the atmospheric pressure ionization-electrospray ionization (API-ESI) MS was used for microcystin-LR detection and quantitation in samples of dried Microcystis aeruginosa cells. An alkaline linear gradient (20 mmol/l ammonium hydroxide-acetonitrile, pH 9.7) was used for elution of the toxic peptides. Limit of detection was 1 microg/ml (20 ng per injection) in the scan mode of MS and 0.1 microg/ml (2 ng per injection) in the case of selective ion monitoring.