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Three-parameter Hill's equation, which is used in enzyme kinetics, was shown to applicable to calibration curves of both potentiometric (glucose, pesticides, urea, etc.) and amperometric (surfactants, biphenyl, etc.) biosensors. Possible causes of errors of analyte concentration measurements are discussed.

The use of biosensors for detecting aromatic compounds (aniline, hydroquinone, phenol, and N,N-dimethyl-p-phenylenediamine), heterocyclic compounds (adenosine, AMP, ATP, bilirubin, hypoxanthine, guanine, inosine, inosine 5'-phosphate, xanthine, creatinine, uric acid, and NAD), carbohydrates (glucose, galactose, lactose, maltose, and sucrose), vitamins, antibiotics, steroids, mutagens, and organophosphorous pesticides is discussed. Basic metrological characteristics of these biosensors are reviewed.

The mathematical models of amperometric biosensors, with single- or two-substrate reaction occurring in their cover, were developed. A linear two-parametric equation of steady state was suggested for the biosensor detecting the product of single-substrate reaction corresponding to the Michaelis-Menten scheme. The conditions of equation applicability to description of standard biosensor kinetics in the wide range of substrate concentration, diffusion-module values, and permeability coefficients of three-layer-cover components were studied.

Urease was immobilized on macroporous silicas using gamma-aminopropyl triethoxysilane and glutaraldehyde. The amount of protein on the surface, the structure of pores of the support and the purity of the initial enzyme were varied, the enzymic activity of the immobilized preparations being controlled. After the immobilization of sufficiently large quantities of the enzyme (about 3 mg protein per m2 support) about 35% of the specific activity was retained. The maximum activity per unit weight of the support was observed for silicagels and silochromes with the mean diameter of pores 70-90 nm and the specific surface area about 70 m2/g. The use of purified urease produced highly active preparations of the immobilized enzyme (17,000 U per g dry support). Freeze-drying of the immobilized enzyme in the presence of sorbitol yielded dry preparations retaining their activity.