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 μg/ml (20 ng per injection) in the scan mode of MS and 0.1 μg/ml (2 ng per injection) in the case of selective ion monitoring.