A new HRP/catalase biosensor based on microconductometric transduction for nitrite determination

An interdigitated conductimetric electrode system using a combination of peroxidase/catalase has been developed to determine nitrite in water samples. A peroxidase (HRP) was located in the inner layer while the outer contained catalase. Catalase catalyzed the breakdown of H2O2 into H2O and O-2 thus consuming totally H2O2, the substrate of HRP. The latter, in presence of H2O2, generates a conductometric signal due to the reduction of H2O2. Nitrite was selected as an inhibitor of catalase. In the presence of H2O2, the nitrite addition blocked the H2O2 consumption by catalase. Since nitrite had no effect on HRP activity, its inhibitive effect on catalase leads to an increase in the conductometric signal. The bienzyme sensor exhibits an increase in conductometric response for nitrite concentration, leading to high values of conductivity. In both case, the detection limit of nitrite is 0.3 mu M and for bienzyme sensor the dynamic range is from 0.3 mu M to 446 mu M. (C) 2009 Elsevier B.V. All rights reserved.