'Biosensors for heavy metal salt measurements with immobilized enzymes on a Clark electrode'

Publisher Summary This chapter focuses on biosensors for heavy metal salt measurements with immobilized enzymes on a Clark electrode. Most immobilized enzymes are sensitive to 1 mM heavy metal salts. After immobilization at the surface of an affinity membrane (Ultrabind from Gelman), some enzymes are much more sensitive to lower concentrations of mercury salts. In a study described in the chapter, 50% inactivation (I50) was obtained with HgCl2 after 2 min incubation. Inactivation of the enzymes was measured with a Clark electrode whose sensitive tip was covered with the immobilized enzyme film. Addition of substrate induces oxygen consumption, which is inhibited by the heavy metal salt. For pyruvate oxidase, the sensitivity was further increased reaching 10 nM when the incubation with HgCl2 was performed in the absence of thiaminepyrophosphate-Mg. The biosensors are very easy to use, and the assay lasts less than 10 s. Applications can be found for solving pollution problems of water.