[Optimal conditions for the functioning of a urease-based biosensor and pH-sensitive field transistors. Determination of urea in solution].

The article deals with the optimal conditions of urea determination in solution by the enzyme sensor based on pH-sensitive field effect transistor. The dependence of response level on temperature, pH, ionic strength, buffer capacity were investigated. 10 mM phosphate buffer, pH 7.4 containing 200 mM NaCl is optimal for possible measurements of urea in diluted blood. Temperature change in the measured samples from 15 degrees to 30 degrees C does not affect the sensor signal value. Stability of immobilized ureas was investigated at storage under different conditions. In the presence of 1 mM EDTA activity of immobilized enzyme does not change during one month storage at 4 degrees C.