Losses of the cyanobacterial toxin microcystin-LR from aqueous solution byadsorption during laboratory manipulations

The effect of plastic and methanol on the loss of microcystin-LR from solut ion was analysed by HPLC with photodiode array detection (HPLC-PDA). With p lastic disposable pipette tips, the loss from an aqueous microcystin-LR (MC -LR) solution was 4.2% per lip operation. Using the same pipette tip, four operations were required to completely saturate a single tip with toxin. MC -LR attached to plastic pipette tips could subsequently be eluted by methan ol and detected by HPLC-PDA. At methanol concentrations below 25% (v/v), re covered concentrations of MC-LR decreased significantly. Differences in MC- LR concentration were also noted by performing 50% dilution with Milli-Q wa ter or methanol. The results are discussed in relation to the hydrophobicit y of MC-LR, analytical procedures and the avoidance of toxin losses from so lution during laboratory manipulations. (C) 2000 Elsevier Science Ltd. All rights reserved.