Yu. G. Vlasov

Evaluation of Italian wine by the electronic tongue: recognition, quantitative analysis and correlation with human sensory perception

Abstract The electronic tongue based on a sensor array comprising 23 potentiometric cross-sensitive chemical sensors and pattern recognition and multivariate calibration data processing tools was applied to the analysis of Italian red wines. The measurements were made in 20 samples of Barbera d’Asti and in 36 samples of Gutturnio wine. The electronic tongue distinguished all wine samples of the same denomination and vintage, but from different vineyards. Simultaneously the following quantitative parameters of the wines were measured by the electronic tongue with precision within 12%: total and volatile acidity, pH, ethanol content, contents of tartaric acid, sulphur dioxide, total polyphenols, glycerol, etc. The electronic tongue is sensitive to multiple substances that determine taste and flavour of wine and, hence, the system was capable of predicting human sensory scores with average precision of 13% for Barbera d’Asti wines and 8% for Gutturnio wines.

Electronic tongue: new analytical tool for liquid analysis on the basis of non-specific sensors and methods of pattern recognition

Abstract Development of promising sensor instrument — “electronic tongue” based on sensor arrays with data processing by pattern recognition methods have been described. The attention is paid to “electronic tongue” based on an array of original non-specific (non-selective) potentiometric chemical sensors with chalcogenide glass membranes. Principles of research, criteria for the development of non-selective sensing materials, pattern recognition methods have been described. Possible applications and some results of integral qualitative analysis of beverages and of quantitative analysis of complex liquids, containing heavy metals are reported. Discriminating power obtained and possibility of multicomponent analysis permit to consider “electronic tongue” as a perspective analytical concept.

Application of electronic tongue for qualitative and quantitative analysis of complex liquid media

Abstract The present work is devoted to the assessment of analytical applications of a new instrument for multicomponent analysis in liquid media — “electronic tongue”, based on an array of originally designed non-specific solution chemical sensors and pattern recognition tools for processing of multidimensional output of this sensor array. The “electronic tongue” is supposed to be capable to produce integral qualitative imaging (artificial sensing) of complex liquids such as food stuffs and beverages, comparable to human taste panel sensing and enhancing its capabilities by durable and reproducible operation, analysis and tasting of toxic and potentially dangerous media, applicability to long-term routine industry analysis. The method is also successfully applicable to quantitative analysis of different objects such from biological liquids to natural waters. Promising experimental results of “electronic tongue” application in different beverages are reported.

Development of multisensor systems based on chalcogenide thin film chemical sensors for the simultaneous multicomponent analysis of metal ions in complex solutions

Abstract A new type of thin film chemical microsensors based on chalcogenide glass-sensitive materials was developed by means of silicon planar technology and pulsed laser deposition technique. These miniaturised ion-selective electrodes (ISEs) exhibit Nernstian responses over five concentration decades with detection limits of 1×10 −7 mol/l towards the primary ions Cu and Pb, and 4×10 −7 and 3×10 −5 mol/l towards Cd and Tl, respectively. The thin film microsensors have been shown to be perspective instruments for the simultaneous multicomponent analysis of complex liquid media based on the principles of an ‘electronic tongue’ device. Incorporating the thin film sensors into a sensor array allowed the multicomponent analysis of heavy metal-ion species (Pb 2+ , Cd 2+ , Zn 2+ and Fe 3+ ). The concentrations of Pb 2+ -, Cd 2+ - and Zn 2+ -ions can be determined simultaneously by direct potentiometric measurements using a sensor array of seven all-solid-state thin film chemical microsensors with an accuracy of 15–30%. The sensor array allows overcoming the problem of an insufficient selectivity of single sensors. The suggested microsystem-compatible fabrication technique favours a further miniaturisation, aimed to a fully integrated electrochemical microsystem.

The features of the electronic tongue in comparison with the characteristics of the discrete ion-selective sensors

Abstract A comparison of the features of the electronic tongue; comprising an array of non-specific chemical sensors and pattern recognition methods, with analytical characteristics of the discrete conventional ion-selective sensors (electrodes) has been performed. A method has been suggested that allows observing the detection limit and the selectivity of a sensor array at least three to five times better than that for a single sensor. The electronic tongue also exhibits a number of completely new features, such as the possibility to determine some unusual species in solutions, e.g. organic substances, and the capability to make measurements without the standard reference electrode.

Chalcogenide glass chemical sensors: Research and analytical applications

The paper is devoted to research and development in the field of chalcogenide glass chemical sensors for determination of heavy metal ions in solution. The overview of the solid-state scientific approach and research design of the sensing materials is followed by the original results of the analytical application of the chalcogenide glass sensors for laboratory analysis, industrial control and environmental monitoring.

Multisensor system on the basis of an array of non-specific chemical sensors and artificial neural networks for determination of inorganic pollutants in a model groundwater

The application of a multisensor system to groundwater monitoring is investigated. The sensor system is based on an array of non-specific potentiometric chemical sensors with data processing by artificial neural networks and includes 13 sensors with PVC membranes and 12 solid-state ones. Results of measurements in model solutions containing heavy metals, alkali- and alkali-earth cations and inorganic anions at concentrations typical for groundwater near the city of Braunschweig, Germany, are presented. Both the response of the whole sensor array and the responses of subsystems consisting only of PVC and only of solid-state sensors, respectively, are investigated. It is shown that both subsystems can be used for determination of described ions and that the best results are obtained if the whole array of sensors is used.

COPPER ION-SELECTIVE CHALCOGENIDE GLASS ELECTRODES Analytical Characteristics and Sensing Mechanism

Abstract New copper ion-selective electrodes based on chalcogenide glasses, CuxAg25−xAs37.5Se37.5, display high copper(II) ion sensitivity with Nernstian response in the range pCu 1–6, short response time, high selectivity, potential stability and reproducibility. These electrodes are 10–30 times more sensitive in strongly acidic media than crystalline copper ion-selective sensors and are superior to the copper(I) selenide electrode in selectivity and resistance to acids and oxidation. A model is proposed to explain the ion sensitivity of these chalcogenide glass sensors. The sensitivity depends on direct exchange of copper(II) ions between solution and the modified surface layer of the glass. The modified surface layer is formed as a result of partial destruction of the glass network on soaking in solution; its atomic density is 2.0–2.5 times less than that of the original glass. The structural defects and hollows make fast copper(II) ion migration within the modified surface layer possible. Exchange sites in this layer can be formed by both disproportionation and oxidation of copper(I) in the glass network, as well as by diffusion of copper(II) ion from solution in the case of glasses with low copper content. Experimental confirmation of this model is provided by x-ray, photo-electron and scanning Auger electron spectroscopy.

Surface plasmon resonance monitoring by means of polarization state measurement in reflected light as the basis of a DNA-probe biosensor

Abstract An approach to the read-out problem of the shift of surface plasmon resonance (SPR) dip and an experimental arrangement for its realization are considered. The principle of the proposed registration method is based on the measurement of the ratio of the p- and s-polarized components in reflected light, giving a sensitive enhancement of up to two orders of magnitude. The described set-up can be employed to monitor biospecific interactions, producing refractive-index changes near the detection limit of the SPR technique using only p-polarized light.

Thin film sensors on the basis of chalcogenide glass materials prepared by pulsed laser deposition technique

Abstract Potentiometric thin film sensors on the basis of the two different chalcogenide glass materials Ag–As–S and Cu–Ag–As–Se–Te have been prepared by means of the pulsed laser deposition (PLD) technique onto Si/SiO2 substrates with an additional contact layer of Cr/Au and Ti/Pt, respectively. The physical layer structure and the stoichiometric composition of the deposited glass materials have been investigated by means of Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). Depending on the material systems used, in a conventional “two-electrodes” measuring set-up, these novel thin film sensors possess a high sensitivity towards lead (23–25 mV/pPb), copper (29–31 mV/pCu), cadmium (23–27 mV/pCd) and silver (about 54 mV/pAg) over a measuring period of more than 60 days. The obtained results are in good accordance when comparing them to measurements performed with conventional bulk ion-selective electrodes, built-up of the same layer composition.