Einflu� von Schwermetallionen in Trinkwasser auf die Aktivit�t des AChE-Biosensors

Abstract

Influence of Heavy Metal Ions in Drinking Water on the Activity of the AChE-Biosensor Because of the specific inhibition of the enzyme acetylcholinesterase (AChE) by organophosphoric ester, -thioester and N-methylcarbamates an acetylcholinesterase biosensor can be used to screen drinking water for the presence of compounds used as insecticides. The presence of heavy metal ions may also lead to a decrease in catalytic activity of the enzyme, and in this way a misinterpretation of the results of the screening is possible. In this paper the effect of lead, iron, copper and zinc ions on the activity was examined, with the view to the concentration limit given by the decree for drinking water in the Federal Republic of Germany. Zinc and copper ions in drinking water produce a detectable inhibition (3 mg/L copper produced an inhibition of 10 to 20%, 5 mg/L zinc an inhibition of 10%), therefore the presence of copper, lead and other heavy metal ions not tested in drinking water may produce wrong results in pesticide screening. The coimmobilization of albumin and enzyme was successfull in eliminating the inhibition caused by heavy metal ions. Using this membrane for a 3 mg/L copper solution an inhibition of only 0.3% higher was measured and for a 5 mg/L zinc solution an inhibition of 2.3% lower than the inhibition of TRIS-buffer itself. This results were in the range of the standard deviation, which means that no inhibition could be measured with this metal ion solution using albumin containing AChE-membranes. The use of this modified membrane in real drinking water samples shows clearly lower inhibition values than that of membranes without albumin.