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Characterization of a Voltammetric Electronic Tongue
Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electronic tongues were developed some ten years ago. These systems consist of an array of nonspecific sensors and a signal processing unit. The sensor signals are processed by pattern recognition methods which makes possible the extraction of specific properties from the sample. Depending on the calibration, attributes such as quality or taste can be determined. These systems also detect changes in the sample that they are not calibrated for which makes possible the detection of anomalous occurrences. Such sensor systems are suitable for process control and surveillance. Important factors are the sensitivity and stability, specifically the sensor's ability to respond to small changes and to provide true and reproducible readings over time. Problems with sensor stability are commonly referred to as drift. The major topic of this thesis is the improvement of long term stability for electronic tongues used in liquid process applications.

Drift counteractions, such as renewal of the electrode surface by polishing, was compared with mathematical correction methods. Since drift is induced by the environment of the sensor, mathematical correctional actions must include reference samples and the induced drift must be identical between measurements. These conditions restrict and complicate the use of mathematical drift counteractions. It was found that mechanical polishing renewed the electrode surfaces, and that the induced drift was unique for each sample. The sample induced drift pattern can be treated as information from the sample, but only if the sensors are renewable in a repeatable way. Applications where polishing the electrode surfaces are necessary to obtain repeatable analyses are described, such as the detection of urea and measurements in corrosive environments such as wine.

Electrochemical oxidation of urea in water is difficult to use for analytical purposes because of residues left on the electrode surface. An important result from this thesis is that mechanical cleaning of the electrodes between samples gives sensor signals that are both repeatable and proportional to the concentrations of urea and glucose. An experimental design was employed for optimal effect of the calibration of urea in the presence of glucose as a disturbance in the sample. The goal was to minimize the correlation between the two analytes. This made possible the prediction of both analyte concentrations.

Wine is a complex sample to analyze with many sources of disturbances for electrochemical measurements. The carefully planned experiments and calibrations reported in this thesis minimized covariance and background effects. A method for prediction of bisulfite, histamine and ascorbic acid concentrations in wine was developed. The method was tested with spiked samples of white-, red-, rose-wines and even apple juice. The reproducibility of the measurements was excellent. Since polishing renewed the electrodes between measurements, a validation performed one month after the calibration was also predicted with good results. This demonstrated that the renewal of the electrodes eliminated special requirements for maintenance and storage of the sensor.

Drinking water surveillance has been performed with an electronic tongue. The potential of using a voltammetric electronic tongue for multicomponent analysis of compounds in drinking water has been evaluated. By using such a non-selective sensor it was possible to detect anomalies without the need of a specific sensor for each type of event. The device can be calibrated for the most likely events, and it can also be used for sensing and alarm when exceptional events occur.

The detection of surface active species like detergents is normally done by titration. An in-line sensor that could control the washing process by detecting the concentrations of detergents during the different steps in a wash cycle could enhance the performance of washing machines. An electronic tongue was used to predict concentrations of detergents in samples from different stages in the washing procedure. The tongue was compared with a much simpler conductivity meter, and due to the covariation of supporting electrolyte, both sensors were able to predict concentrations of ionic surfactants. The electronic tongue showed promising results in predicting also non ionic surfactants where the conductivity meter failed. The detection mechanism was probably due to shielding the electrode surface from electro active species in the samples.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press , 2010. , 42 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1267
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-65414ISBN: 978-91-7393-554-8 (print)OAI: oai:DiVA.org:liu-65414DiVA: diva2:395493
Public defence
2010-05-12, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2011-02-07Bibliographically approved
List of papers
1. A self polishing electronic tongue
Open this publication in new window or tab >>A self polishing electronic tongue
2006 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 118, no 1-2, 461-465 p.Article in journal (Refereed) Published
Abstract [en]

An investigation to obtain reproducible measurements with a pulse voltammetric electronic tongue has lead to the development of self polishing device. A grit paper covered bar rotating over the working electrodes is performing the polishing, to avoid measurements while the polishing bar covers the electrodes an angular decoder is fitted. Measurements in buffer, 2 mM K3[Fe(CN)6] and a buffered tea samples shows that polishing reduces drift, sensitivity decreases with electrode fouling, pre-treatment or conditioning of electrodes post polishing must be optimised concerning the analyte. Also found was that drift due to electrode fouling is a repeatable mechanism which pattern can be used to increase information about the analyte. © 2006 Elsevier B.V. All rights reserved.

Keyword
Drift, Electronic tongue, Renewable electrodes, Sensitivity, Voltammetry
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-50101 (URN)10.1016/j.snb.2006.04.042 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2017-12-12
2. Determination of detergents in washing machine wastewater with a voltammetric electronic tongue
Open this publication in new window or tab >>Determination of detergents in washing machine wastewater with a voltammetric electronic tongue
2008 (English)In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 76, no 1, 91-95 p.Article in journal (Refereed) Published
Abstract [en]

A voltammetric electronic tongue (ET) and a conductivity meter were used to predict amounts of detergents in process water from washing machines. The amount of detergent in over sixty samples was also determined by a HPLC reference method. Prediction was more accurate for the electronic tongue, but both techniques could be used. The composition of the detergent, e.g. supporting electrolyte, is an important factor for the ability to predict the detergent quantity by conductivity. Also two different surfactants, alkyl benzyl sulfonate (ABS) and etoxylated fatty alcohol (EOA), were fingerprinted by the HPLC. Their behaviour during the wash cycle differs from each other, ABS rinses away in the same proportions as the supporting electrolyte, but EOA appears to stay within the machine and laundry. Prediction models for ABS are accurate both with ET and conductivity meter, mostly due to the correlation with supporting electrolyte. The behaviour of EOA, with almost no correlation to the supporting electrolyte makes it difficult to predict using conductivity but ET prediction models give promising indications of its capabilities. © 2008 Elsevier B.V. All rights reserved.

Keyword
Detergents, Electronic tongue, HPLC, Surfactants
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-45944 (URN)10.1016/j.talanta.2008.02.028 (DOI)
Available from: 2009-10-11 Created: 2009-10-11 Last updated: 2015-09-18
3. Determination of Bisulfites in Wines with an Electronic Tongue Based on Pulse Voltammetry
Open this publication in new window or tab >>Determination of Bisulfites in Wines with an Electronic Tongue Based on Pulse Voltammetry
Show others...
2009 (English)In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 21, no 3-5, 612-617 p.Article in journal (Refereed) Published
Abstract [en]

An electronic tongue (ET) based on pulse voltammetry is used to predict concentrations of bisulfites in wine samples. The ET array consists of four working electrodes (gold, rhodium, platinum and stainless steel) encapsulated into a stainless steel cylinder used at the same time as both the body of the ET system and the pseudoreference/counter electrode. The ET device is additionally equipped with a self-polishing system. Multivariate analysis including Cross validation and partial least square (PLS) techniques are applied for data management and prediction models building. Ascorbic acid and histamine have also been included in the predictive analysis.

Keyword
Electronic tongue, Pulse voltammetry, Bisulfite, Prediction model, PLS
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17513 (URN)10.1002/elan.200804457 (DOI)
Available from: 2009-03-27 Created: 2009-03-27 Last updated: 2011-02-07
4. A Flow System for Urea and Glucose Measurement with a Self Polishing Electronic Tongue
Open this publication in new window or tab >>A Flow System for Urea and Glucose Measurement with a Self Polishing Electronic Tongue
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A self polishing voltammetric electronic tongue was evaluated for simultaneousl prediction of urea and glucose concentrations in phosphate buffer in a flow system. The voltammetric electronic tongue consisted of three working electrodes (gold, platinum and rhodium) and a counter electrode, also acting as reference electrode. The flowsystem contained five valves, controlled by a computer and a peristaltic pump. Two batches of sample standards were used; one for calibration and the other for validation. The system could predict concentrations of urea and glucose in the interval 0 – 20 mM in the validation batch. No significant difference between the two batches was seen. The self polishing approach makes the system in principle maintenance free. With a large potential use in hemodialysis.

Keyword
Voltammetry, electronic tongue, urea, glucose, multivariate data analysis
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65409 (URN)
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2011-02-07Bibliographically approved
5. Multicomponent analysis of drinking water by a voltammetric electronic tongue
Open this publication in new window or tab >>Multicomponent analysis of drinking water by a voltammetric electronic tongue
2011 (English)In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 683, no 2, 192-197 p.Article in journal (Refereed) Published
Abstract [en]

A voltammetric electronic tongue is described that was used for multicomponent analysis of drinking water. Measurements were performed on drinking water from a tap and injections of the compounds NaCl, NaN3, NaHSO3, ascorbic acid, NaOCl and yeast suspensions could be identified. A PLS based model was developed for the simultaneously prediction of identification and concentration of the compounds NaCl, NaHSO3 and NaOCl .By utilizing this type of nonselective sensor technique for water quality surveillance, it will be feasible to detect a plurality of events without the need of a specific sensor for each type of event.

Place, publisher, year, edition, pages
Elsevier, 2011
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65410 (URN)10.1016/j.aca.2010.10.027 (DOI)000286854700006 ()
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2017-12-11
6. In situ studies of electrode regeneration by polishing during measurements
Open this publication in new window or tab >>In situ studies of electrode regeneration by polishing during measurements
(English)Manuscript (preprint) (Other academic)
Abstract [en]

A general problem for all electronic tongues (and for most other sensor systems), especially when measuring in crude and complex media, is electrode fouling. The possibility of using a selfpolishing voltammetric electronic tongue has been investigated using cyclic voltammetry. The tested compounds were potassium hexacyanoferrat(II) (K4Fe(CN)6) and urea, respectively. Effects of short term drift, directly after polishing before the electrode is completely equilibrated, are repeatable.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-65412 (URN)
Available from: 2011-02-07 Created: 2011-02-07 Last updated: 2011-02-07Bibliographically approved

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