V. V. Kolodnikov

Chemical sensors and their systems

The review presents a short record of the evolution of chemical sensors (ion selective electrodes) and multisensor systems of an electronic tongue type, based on the organization principles similar to those of biological sensors. The main types of chemical sensors and multisensor electronic tongue combinations elaborated today are considered along with sensitive materials used in them. Recent advances in chemical sensors, for example, lower detection limits and so-called true selectivity are scrutinized. Also, some widespread analytical applications of electron tongues, including those for the identification and classification of liquid media, for the quantification of various components in there, for the control of industrial processes, as well as the type and intensity evaluation of the taste of food and medications are discussed.

Determination of cyanide using flow-injection multisensor system

A flow-injection multisensor system (FIMS) comprising potentiometric sensors of different types for determination of free cyanide activity in basic solutions for extraction of noble metals was developed. The solvent polymeric membrane sensors based on metalloporphyrin and crystalline sensors were combined in the sensor system. The system allowed determination of cyanide activity in the range 10(-4)-1 mol l(-1) with an error less than 5% in individual cyanide solutions and acceptable precision (about 20%) in process liquids. The system was able to analyse up to 20 samples per h. The FIMS was also applied to detecting of silver ions in the presence of cyanide. Chalcogenide glass sensor was used as the detector that ensured the precision of 20%.

Thallium-selective sensor with a membrane based on Tl4HgI6 ionic conductor

Tl4HgI6 solid electrolyte with a high ionic component of conductivity was synthesized for developing a thallium-sensitive sensor. The main sensor characteristics (tilt angle, detection limit, selectivity, pH range, potential drift) of the new thallium sensor were determined. The time stability of its operation and various ways of its application for determining thallium ions in solutions are demonstrated.

Diffusion of silver and ionic conductivity in the solid electrolytes Ag8HgS2I6 and Ag6I4WO4

Abstract Ionic conductivity and silver diffusion in the Ag8HgS2I6 and Ag6I4WO4 superionic conductors have been studied. The obtained diffusion coefficients of the silver ions are in equations: Ag8HgS2I6 (100–260°C) D ∗ =2.3×10 −4 exp (−0.128 eV /kT) , Ag6I4WO4 (100–200°C) D ∗ = 6.0×10 −4 exp (−0.183 eV /kT) . The calculated values of Haven ratio confirm the existence of essential differences in transfer properties for the solid electrolytes with α-AgI-type structure.

The nitrate-selective sensor with crystalline membrane

Abstract The nitrate-selective sensor developed in the Laboratory of Chemical Sensors of St. Petersburg University has been applied for the potentiometric determination of the nitrate ion in solution. It was found that the linear Nernstian response is from 1 to 6 pNO 3 for these sensors. A simple analytical procedure for the nitrate-ion determination with crystalline membrane sensors can be used for environmental and industrial monitoring and various analytical performances.