Inhibitive determination of mercury and other metal ions by potentiometric urea biosensor

The biosensor with urease entrapped in PVC layer at the surface of pH-sensitive iridium oxide electrode was applied for testing of mercury and other metal ions inhibition on enzymatic reaction. The calculation of inhibition effect was based on the measurement of initial rate of decrease of biosensor potential (proportional to the initial rate of enzymatic reaction) after addition of substrate after inhibition step. Some differences of inhibition extent were observed for various mercury forms (Hg(NO 3) 2, HgCl 2, PhHgCl and Hg 2(NO 3) 2) as well as for other heavy metal ions investigated as potential interferents. Because the method was not specific, it was applied for the determination of total inhibition effect caused by heavy metal ions in water samples. In the case of most cations tested the total recovery of enzyme activity was possible using Tris buffer solution with EDTA and thioacetamide after less than 10 min regeneration time.