Amperometric detection of hydroxypurines at an electrode modified with a composite based on mixed-valence ruthenium and cobalt oxides in flow injection analysis

A composite material based on mixed-valence ruthenium and cobalt oxides, electrodeposited on the surface of a screen printed electrode, exhibits high catalytic activity in the electrooxidation of uric acid, xanthine, and hypoxanthine. Catalysis manifests itself as a decrease in the substrate oxidation overvoltage and an increase in current at the potential of modifier oxidation. A method is proposed for the simultaneous amperometric detection of two-component systems uric acid–xanthine, xanthine–hypoxanthine, and uric acid–hypoxanthine using a screen printed electrode with two working electrodes modified by this composite. The dependence of the analytical signal on the concentration of analytes is linear in the range 5 × 10^–8 to 5 × 10^–3 M for uric acid and xanthine and from 5 × 10^–7 to 5 × 10^–3 M for hypoxanthine.     

Amperometric Cholinesterase Biosensors with Carbon Paste Electrodes Modified with Cobalt Phthalocyanine

Biosensors based on a carbon paste electrode with immobilized cholinesterase and cobalt(II) phthalocyanine as a mediator are studied. Electrochemical characteristics of the biosensors are investigated in relation to the carbon paste composition, the enzyme and mediator immobilization procedures, nature of the protective film and procedure of its application, and also storage conditions of the electrodes. A method is suggested for fabricating a cholinesterase biosensor with cobalt(II) phthalocyanine mediator, providing the maximum electrocatalytic response in electrooxidation of butyrylthiocholine iodide (substrate for cholinesterase).     

Electrocatalytic oxidation and amperometric detection of ethanol on graphite electrodes modified with a coating composed of hexacyanometallates

The electrochemical behavior of methanol on graphite electrodes modified with a coating composed of (III) hexacyanoferrate and ruthenium(III) hexacyanoferrate(II) and hexacyanoruthenate(II) was studied. A method for electrochemical determination of ethanol on a carbon-paste electrode modified with a coating composed of ruthenium(III) hexacyanoruthenate(II) under stationary and flow-injection conditions was suggested.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 12, 2004, pp. 1974–1979.Original Russian Text Copyright © 2004 by Shaidarova, Gedmina, Chelnokova, Budnikov.     

Electrocatalytic oxidation and flow-injection determination of ascorbic acid at a graphite electrode modified with a polyaniline film containing electrodeposited palladium

A method for forming a composite film on the surface of a graphite electrode is proposed. Conditions for detecting the maximum catalytic current under batch and flow conditions are determined. A procedure for the electrocatalytic determination of ascorbic acid at the graphite electrode modified with a polyaniline film containing palladium particles is proposed. The catalytic effect of this electrode manifests itself by a ～300-mV decrease in the peak potential of ascorbic acid oxidation and by a multiple increase in the peak current of ascorbic acid oxidation as compared to the unmodified electrode. The linear dependence of the electrocatalytic response of the composite electrode on the concentration of ascorbic acid is observed down to 1 × 10^?8 M and 2.5 nmol of ascorbic acid under batch and flow-injection analysis conditions, respectively.     

Voltammetry determination of dopamine by the electrocatalytic response of an electrode modified by a polyaniline film with an inclusion of copper(II) tetrasulfophthalocyanine

A polyaniline composite film with an inclusion of copper(II) tetrasulfophthalocyanine, applied on a glassy-carbon electrode (GC) has demonstrated a mediatory activity in the oxidation of dopamine in acidic and neutral media. The conditions for the formation of a polymer film on the surface of a glassy-carbon electrode for registering the maximum electrocatalytic effect in the oxidation of dopamine are found. A method of voltammetric and amperometric detection of dopamine on the composite film electrode under static and flow conditions is proposed. The use of a polyaniline composite with an inclusion of copper(II) tetrasulfophthalocyanine, coated with a Nafion film, made possible the reduction of the detection limit for dopamine to 1 × 10^?8 M under static conditions and to 5.0 nmol under the conditions of flow-injection analysis.