Chiang Mai Journal of Science

Analysis of microcystins in Thailand is of interest due to Microcystis aeruginosa bloom in some freshwater reservoirs. Toxin analysis has been done and included in water quality monitoring. During water sampling, toluene as preservative was added to cover surface of water sample. It acts as a barrier between the air and the surface of the specimen. In this work, the effects of preservative chemicals including toluene and sodium azide were tested with permeabilised Microcystis. Toluene was found to act as accelerator of toxins release from cells to their environment. Samples without toluene contained almost 100% microcystins in their pellets. A release of microcystins from the cells was found in all samples with spiked toluene. Microcystins detected in supernatants of the samples with toluene were much higher than in those without toluene. Percentage of the toluene added was found to be related with a rate of toxin release as well as storage time. Long storage period presented low amount of microcystins detected in the pellets, whereas their high amount were found in the aqueous part. In comparison with added sodium azide samples, no major change had been observed on concentrations of microcystins both presented in pellet and supernatant in relation with time. Lyophilised Microcystis bloom materials from Sakon Nakhon Province, Thailand was also tested with toluene in order to see its effect on natural sample. We found a possible biotransformation peak that increases while the others are decreasing. It is possible that the biotransformation remains stable and at low concentrations when sterile, but increases when no sterile. In conclusion, sodium azide seemed to be more effective for preservation of microcystins in cells because no major change had been observed on concentrations of microcystins presented in pellet and supernatant in relation with time.