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 O₂ 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 µM and for bienzyme sensor the dynamic range is from 0.3 µM to 446 µM.