Direct determination of cyanides by potentiometric biosensors

Cyanide (CN-) and its derivatives are widely used in the metal mining and metal plating industry. But also many medicinal and food plants are toxic for man because of their content of cyanogenic glycosides. In the present investigation, a cyanide-specific biosensor exploiting immobilized cyanidase (EC 3.5.5.1) has been developed. Enzymatically formed ammonia was either detected by a potentiometric sensor based on an ammonia electrode or by a pH-sensitive electrolyte/insulator/semiconductor (EIS) layer structure made of Al/p-Si/SiO2/Si3N4. It could be demonstrated with both methods that sensitivity of these biosensors is sufficient to detect cyanide in sub-toxic concentrations. The detection limit was determined to be in the micromolar concentration range. (C) 2004 Elsevier B.V. All rights reserved.