Profiling microcystin contamination in a water reservoir by MALDI-TOF and liquid chromatography coupled to Q/TOF tandem mass spectrometry

High resolution mass spectrometry was employed to study a bloom of the Cyanobacterium Planktothrix rubescens in a dam for drinking water on Lake Occhito, near the town of Foggia, in Southern Italy, to characterise the cyanotoxins produced and to evaluate the related health risks for consumers.The cyanotoxin production in various sites of the contaminated dam was studied by MALDI-TOF mass spectrometry and liquid chromatography coupled to Q/TOF tandem mass spectrometry analysis of water and cyanobacteria samples. MALDI-TOF mass spectrometry was employed for rapid screening over a wide mass range; liquid chromatography coupled to Q/TOF tandem mass spectrometry allowed for molecular structure confirmation of each single cyanotoxin. This analytical strategy allowed for profiling the cyanotoxins produced during the bloom and calculating the concentrations of the main contaminants in drinking water.Microcystins, anabaenopeptins and aeruginosins were the main cyanotoxins identified. A des-methyl variant of the microcystin-RR was recognised as the most abundant compound in all water samples; liquid chromatography coupled to Q/TOF tandem mass spectrometry allowed for molecular structural confirmation of detected substances, and quantitative analysis of microcystins. The contamination levels over 3 weeks were monitored, by sampling from different sites of the dam.This analytical strategy allows for complete characterisation of the cyanotoxins produced during this kind of environmental outbreaks, for time-dependent monitoring of pollution levels and thus represents a powerful tool to prevent intoxication for consumers of contaminated drinking water collected from the dam.