BLÅGRÖNALGETOKSINER I DRIKKEVAND - INTRACELLUL/ERE LEVERTOKSINER FRIGIVES KUN DELVIST VED NEDFRYSNING AF VANDPRÖVER / Blue-green algal toxins in drinking water - only partial release of intracellular hepatotoxins through freezing of water samples
Quantification of toxins from blue-green algae (cyanobacteria), particularly the hepatoxic microcystins, has become a routine procedure in assessment of drinking-water quality in many countries. The effect of storing water samples frozen prior to toxin analysis was examined using a laboratory culture of Planktothrix agardhii. In culture material prepared (filtered and toxins in the culture medium concentrated by solid phase extraction) for toxin analysis by HPLC immediately after sampling, 100% of the two major toxins [D-Asp3] microcystin-LR and [D-Asp3]microcystin-LR were intracellular. When culture samples were frozen prior to analysis, 56 % of both toxins were found as free toxins in the culture medium while 44 % remained intracellular. The results illustrate that freezing of water samples may release only about half of the intracellular toxins to the water.