CYANIDE DETERMINATION BY AN ISFET-BASED PEROXIDASE BIOSENSOR

Horseradish peroxidase immobilized on the surface of an Ion Sensitive Field Effect Transistor (ISFET) can be used for the determination of c yanide ions in aquatic media. When the enzyme is immobilized in BSA ge l, the resulting sensor can determine 10(-5)-10(-3) M cyanide. Enzyme immobilization into a positively charged polymer, poly(4-vinylpyridine -co-styrene) (PVPy), seems to cause an increase in cyanide inhibition effects because of anion accumulation in the polymeric matrix, and the resulting sensor can measure cyanide concentration in the range 10(-7 )-10(-5) M. Fifty percent peroxidase inactivation was observed with 80 mu M KCN in the case of BSA-entrapped enzyme, and with only 0.6 mu M KCN when the enzyme was covered by PVPy film. Because of the reversibl e nature of peroxidase inhibition with cyanide ions, restoration of th e enzyme activity after inhibition can be obtained by sensor rewashing in fresh buffer. (C) 1998 Elsevier Science S.A. All rights reserved.