Study on New Extraction Method of Microcystins from Cyanobacteria

A new analytical method of cyanobacterial toxins, i, e, microcysins was deveeloped using supercritical fluid extraction(SFE). The microcystins mcluded in the study are sparsely soluble in neat supercritical fluid CO However, the microcystins were successfully extracted with a temary mixture(90% CO,9.0% methanol 1.0% water) at 40C and 250 atm. The SFE method developed in this study has several advantages over solid-phase extraction(SPE) sample preparation for the analysis of microcystins. Sample handling steps are minimized thus reducing possible losses of analytes and saving analysis time. No clean-up steps are employed in this SFE method. Althouhgh many methods have been described for microcystim RR and LR, the method using solid-phase extraction with ODS cartridges is the most commonly used. However, the adsorbing power of ODS caridges for microcystins is weak, so we have attempted to use a more polar CN cartridge, to increase the adsorbing power for microcystins. Lyophilized cells(100mg) were wxtracted with 5% (v/v) acetic acid. The extract was centrifuged and then the supernatant was applied to a CN cartridge. The cartridge which contained microcystins was rinsed with 5 ml of water and 5 ml of 0.5 M acetic acid. followed by 5 ml of 5% acetonitrile in water , and were determined by HPLC. Better recoveries and chromatogram were observed than with ODS cartridge.