Determination of Organonitriles Using Enzyme-Based Selectivity Mechanisms. 1. An Ammonia Gas Sensing Electrode-Based Sensor for Benzonitrile
Zhaohui Liu, Yi Wang, Samuel P.
Kounaves*, and Edward Brush
Department of Chemistry, Tufts University, Medford, Massachusetts 02155
Organonitriles are considered an important class of compounds which contribute to environmental pollution. A nitrile sensor was developed to directly and selectively measure nitrile compounds in water. Rhodococcus sp. nitrilase catalyzes the hydrolysis of benzonitrile derivatives directly into the corresponding carboxylic acid and ammonia. The enzyme was purified and physically entrapped onto the tip of an ammonia gas sensing electrode using cellulose dialysis membranes. The resulting nitrile sensor was relatively stable for up to four days at 4°C, after daily use at room temperature. It can be reliably used in the pH range of 6-9. The sensor is demonstrated for the detection of benzonitrile in neat water samples at concentration levels as low as 1 x 10-5 M.