Supercritical Fluid Extraction of Microcystin LR from Cyanobacteria using Aqueous Acetonitrile Modifier

The use of supercritical fluids for the analytical extraction of the nonvolatile, higher molecular weight compound, microcystin LR, from cyanobacteria was investigated. The microcystin LR included in this study was sparingly soluble in neat supercritical fluid CO2. However, the microcystin LR was successfully extracted with a ternary mixture (90% CO2, 9.5% acetonitrile, 0.5% water) at 40°C and 250 atm. The polar carbon dioxide‐aqueous acetonitrile fluid system gave a high extraction efficiency for the extraction of the polar microcystin LR from cyanobacteria. In our laboratory, in the past, aqueous acetic acid‐modified CO2 was used for the extraction of microcystins from cyanobacteria and aqueous methanol was also used as a modifier. In this study, we tried a new organic solvent, aqueous acetonitrile as a co‐solvent, so that we could obtain a higher extraction efficiency of the microcystin LR from cyanobacteria than in earlier experiments.