Optimised extraction of microcystins from field samples — a comparison of different solvents and procedures

Cyanobacterial cells of water blooms from various lakes dominated by Microcystis spp., Planktothrix agardhii or Planktothrix rubescens as well as three cultures of cyanobacteria were extracted with either pure methanol, water, 5% acetic acid, 75% aqueous methanol or a sequential extraction using methanol followed by water. It was found that methanol did not extract microcystins quantitatively from lyophilised cyanobacterial field samples. Quantitative extraction could only be obtained by the use of 75% methanol or the sequential extraction. For the extraction of microcystins from lyophilised cyanobacterial field samples we recommend the use of 75% methanol because of better reproducibility and faster procedure compared to the sequential extraction.