Andrey Legin

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.

Tasting of beverages using an electronic tongue

An electronic tongue based on the sensor array of non-specific solution sensors together with pattern recognition tools has been applied to qualitative analysis of different beverages. It has been found that it is capable both to discriminate reliably between various sorts of the same type of beverages (tea, coffee, beer, soft drinks, juice, etc.) and to monitor the process of aging of juice. Correlations have been found between integral parameters produced by electronic tongue and quality of juice. Some conceptions and backgrounds used for electronic tongue development have been put forward and discussed.

Multicomponent analysis on polluted waters by means of an electronic tongue

In this paper the simultaneous measurements of the concentrations of a number of chemical species in solutions performed by a sensor array of ion sensitive electrodes are presented and discussed. By analogy with the well known electronic nose this sensor array operating in solutions, will be here called electronic tongue. In order to extract optimized information from the electronic tongue output data, many different techniques have been applied; they were based on chemometrics, non-linear least squares and neural networks. The best results have been achieved by the introduction of modular models which make use, at the same time, of both qualitative and quantitative information.

All-solid-state electronic tongue and its application for beverage analysis

Disposable all-solid-state planar-type potentiometric electronic tongue has been developed with the carbon paste electrode array screen-printed on a polymeric substrate. Highly cross-sensitive solvent polymeric membranes based on different matrices [e.g. poly(vinyl chloride) (PVC), aromatic polyurethane, and polypyrrole (Ppy)] and doped with common electroactive components for potentiometric measurements (e.g. various plasticizers, and cation- and anion-selective ionophores) were deposited on the screen-printed carbon paste electrodes (SCPEs). It was observed that an incorporation of 10 wt.% of Prussian Blue (PB; Fe4(III)[Fe(II)(CN)6]3) into a commercially available carbon paste and electrochemical preanodization of SCPEs in KCl solution at 1.6 V provide the all-solid-state planar-type electrodes with significantly improved potentiometric stability. The proposed fabrication method gives possibility for simple and reproducible mass-production of low-cost disposable electronic tongue microsystems. The practical utility of all-solid-state disposable electronic tongue chips has been demonstrated with a flow injection cell for the analysis of potable waters, soft drinks, and beers. It is shown that the potentiometric measurements with the SCPE-based all-solid-state chips and the combined use of chemometric methods (e.g. principal components analysis, partial least regression (PLS), and principal component regression (PCR)) for the analysis of obtained data sets successfully discriminate various types of samples according to their tastes.

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.

Cross-sensitivity evaluation of chemical sensors for electronic tongue: determination of heavy metal ions

The development of the promising new field of sensor applications, multisensor arrays for liquid analysis based on the principles of the electronic tongue, implies some new demands on sensor material research and development. Stable and reproducible sensors with partial specificity and considerable cross-sensitivities to different components in solutions are of primary interest. Solid-state potentiometric sensors, both crystalline and vitreous, are likely to be the most promising ones for multisensor devices designed for long-term analytical application in natural and artificial complex media. The present paper deals with development of a method of evaluation of integral heavy metal cation sensitivity of solid-state sensors with special consideration of cross-sensitivity features. The method involves a comparative study of different sensor materials in individual component solutions, using several criteria based on integral response parameters. The procedure scheme can be applied to evaluate cross-sensitivity of any kind of potentiometric sensors for liquid media.

Instrumental measurement of beer taste attributes using an electronic tongue

The present study deals with the evaluation of the electronic tongue multisensor system as an analytical tool for the rapid assessment of taste and flavour of beer. Fifty samples of Belgian and Dutch beers of different types (lager beers, ales, wheat beers, etc.), which were characterized with respect to the sensory properties, were measured using the electronic tongue (ET) based on potentiometric chemical sensors developed in Laboratory of Chemical Sensors of St. Petersburg University. The analysis of the sensory data and the calculation of the compromise average scores was made using STATIS. The beer samples were discriminated using both sensory panel and ET data based on PCA, and both data sets were compared using Canonical Correlation Analysis. The ET data were related to the sensory beer attributes using Partial Least Square regression for each attribute separately. Validation was done based on a test set comprising one-third of all samples. The ET was capable of predicting with good precision 20 sensory attributes of beer including such as bitter, sweet, sour, fruity, caramel, artificial, burnt, intensity and body.

Multicomponent analysis of Korean green tea by means of disposable all-solid-state potentiometric electronic tongue microsystem

Abstract All-solid-state ‘electronic tongue’ microsystem comprised of polymeric sensors of different types such as highly cross-sensitive sensors based both on PVC and aromatic polyurethane (ArPU) matrices doped with various membrane active components, electrochemically deposited conductive films of polypyrrole (PPy) and polyaniline (PAn) and potentiometric glucose biosensors has been developed and applied for the analysis of beverages: natural coffee, black tea and different sorts of green teas. The system can discriminate different kinds of teas (black and green) and natural coffees. Components that are responsible for giving unique taste such as caffeine, catechines, sugar, amino acid l -arginine have been determined for green tea samples with unknown manufacturer specifications.

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.