AbstractThe suitability of pressurized liquid extraction (PLE) of cyanotoxins from cells was investigated. The stability of cyanotoxins (MCYST‐RR, MCYST‐LR, and anatoxin‐a) was evaluated at nine combinations of pressure and temperature (7, 10, and 14 MPa and 60°C, 80°C and 100°C) using 75% (v/v) methanol in water (MeOH) as solvent. Additional experiments investigated the stability of cyanotoxins when water was used as solvent (at a pressure of 14 MPa and a temperature of 40°C, 50°C, 60°C, 80°C, or 100°C). Results using 75% MeOH showed that the MCYST‐RR and MCYST‐LR were stable under the tested pressures up to 80°C. At 100°C MCYST recovery decreased by 10% to 17%. When water was used as the solvent, no differences in recovery were observed for MCYST‐LR, whereas for MCYST‐RR, maximum recovery was obtained at 60°C, and degradation occurred at 100°C. In contrast, anatoxin‐a was labile under all experimental conditions; the best recoveries (ca. 50%) were obtained at 60°C at the three pressures using 75% MeOH. However, only 17%–23% recovery was obtained with water extraction at all temperatures. The extraction of MCYST‐LR and variants from cells (Microcystis aeruginosa, UTCC299) was studied using two solvents, 75% MeOH and 100% water, at 14 MPa and 60°C and 100°C. PLE extracts were compared with extracts obtained with 75% MeOH and ultrasonication. Complete extraction was achieved in both solvents in one 5‐min cycle (at 100°C). Although lower recovery was obtained using PLE (79%–105%), shorter extraction time and automation are advantageous over ultrasonication. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 390–396, 2005.