Table of Contents

Abstract: A planar amperometric glucose microsensor based on glucose oxidase immobilized by chitosan film on Prussian Blue layer has been developed. The experimental results show that the optimum detection potential is 50 mV (versus Ag/AgCl) and the optimum pH is 6.5. Under the selective conditions the sensor exhibits excellent sensitivity of 98 nA/M and a linear range of 0.1-6.0 mM. The apparent Michanelis-Menten constant of the sensor is 21 mM. The response time is less than 60 seconds. No apparent change in the response to glucose was observed during one month. Foremost, the interference of ascorbic and uric acids can be avoided due to selective permeability of chitosan film and electrocatalysis of PB layer to H₂O₂. The sensor has been applied to detect glucose in human blood serum.

Abstract: The purpose of this paper is to study the concept of asymptotic regional observer in connection with the characterizations of sensors. We give various results related to different types of measurements, of domains and boundary conditions. Furthermore, we show that the measurements structures allow the existence of regional observer and we give a sufficient condition for such observer. We also show that, there exists a dynamical system for the considered system is not observer in the usual sense, but it may be regional boundary observer.

Abstract: Results obtained in potentiometric titrations of Fe(II), Mn(II), Fe(CN)₆^4-, C₂O₄^2- and As(III) with standard potassium permanganate solution, are presented. The titration end point (TEP) was detected with a universal electrode whose sensor is natural crystalline pyrite. The titrations of As(III) were carried out in HCl (1.2 M) and H₂SO₄ solutions (0.1- 4.5 M), whereas oxalate was determined in H₂SO₄ (0.1-4.5 M). Iron(II) and hexacyanoferrate(II) were titrated in H₂SO₄ and also in H₃PO₄ solutions (0.1-4.5 M). The titrations of Mn(II) were performed in H₂P₂O₇^2- media at pH 4.0, 5.0, 6.0 and 7.0. The results obtained by using the pyrite electrode were compared with those obtained by the application of a Pt-electrode, and good agreement, reproducibility and accuracy were obtained. The potentials in the course of the titration and at the end-point (TEP) are rapidly established. The potential changes at the TEP ranged from 90 to 330 mV/0.1 mL, depending on the titrated system. The highest changes were observed in titrations of Fe(II) in H₃PO₄ (240-330 mV/0.1 mL). Reversed titrations were also performed and accurate and reproducible results were obtained.