OPTIMIZED EXTRACTION OF MICROCYSTINS FROM FIELD SAMPLES - A COMPARISON OF DIFFERENT SOLVENTS AND PROCEDURES

Cyanobacterial cells of water blooms from various lakes dominated by M icrocystis spp., Planktothrix agardhii or Planktothrix rubescens as we ll 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 methano l did not extract microcystins quantitatively from lyophilised cyanoba cterial field samples. Quantitative extraction could only be obtained by the use of 75% methanol or the sequential extraction. For the extra ction of microcystins from lyophilised cyanobacterial field samples we recommend the use of 75% methanol because of better reproducibility a nd faster procedure compared to the sequential extraction. (C) 1998 El sevier Science Ltd. All rights reserved.