Development of a validated direct injection-liquid chromatographic tandem mass spectrometric method under negative electrospray ionization for quantitation of nine microcystins and nodularin-R in lake water.

•A validated UHPLC-(ESI-)MS/MS method for the quantitation of nine microcystins and Nodularin-R in lake water was developed.•Only centrifugation was adopted during sample preparation, which significantly increase sample throughput.•The developed method was applied to investigate microcystins contamination in five lakes from China.