A possibility of the creation of potentiometric biosensor by adsorption of enzyme urease on zeolite was investigated. Several variants of zeolites (nano beta, calcinated nano beta, silicalite, and nano L) were chosen for experiments. The surface of pH-sensitive field-effect transistors was modified with particles of zeolites, and then the enzyme was adsorbed. As a control, we used the method of enzyme immobilization in glutaraldehyde vapour (without zeolites). It was shown that all used zeolites can serve as adsorbents (with different effectiveness). The biosensors obtained by urease adsorption on zeolites were characterized by good analytical parameters (signal reproducibility, linear range, detection limit and the minimal drift factor of a baseline). In this work, it was shown that modification of the surface of pH-sensitive field-effect transistors with zeolites can improve some characteristics of biosensors.

Different modifications of the zeolites Na+‐Beta and LTA were applied for improving the working characteristics of a urea biosensor. The bioselective membrane of the biosensor was based on urease and different zeolites co‐immobilized with bovine serum albumin on the surface of a pH‐FET. It was shown that the biosensors modified with the zeolites H+‐Beta30 and H+‐Beta50 are characterized by increased sensitivity to urea. The influence of the zeolite concentration on the sensitivity of the biosensors was studied. The optimal concentration of the zeolites H+‐Beta30 and H+‐Beta50 in the bioselective membrane was 15 %. Different variants of co‐immobilization of urease and zeolite H+‐Beta30 were studied and the optimal method was selected. Thus, a general conclusion is that the urea biosensor sensitivity can be improved using zeolite H+‐Beta30 for urease immobilization in the bioselective membrane.