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  • 1.
    Bjorklund, Robert
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Louthander, Dan
    Senset AB, Linkoping.
    Martensson, Per
    Senset AB, Linkoping.
    Andersson, Staffan
    Billerud Skarblacka AB, Skarblacka.
    Kvist, Erland
    Billerud Skarblacka AB, Skarblacka.
    Ohrn, Margareta
    Billerud Skarblacka AB, Skarblacka.
    Krantz-Rülcker, Tina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Online monitoring of inorganic cooking chemicals in white liquor by pulse voltammetry2010In: TAPPI JOURNAL, ISSN 0734-1415, Vol. 9, no 8, p. 49-53Article in journal (Refereed)
    Abstract [en]

    White liquor parameters in the recovery area of a kraft pulp mill were monitored for a 1-year period using rhodium as an electrode material in a sensor system based on pulse voltammetry. Shift personnel performed offline titration analysis of the liquor every 4 hours. The results for effective alkali, sulfidity, and total titratable alkali were used to train and validate the sensor for online monitoring. Partial least square regression models developed from 150 reference titration results for each parameter from the first month of the study predicted concentrations for the following 11 months. Validation of the models using titration results indicated that overall relative root mean squared errors for prediction of the parameters were 3.7% for effective alkali, 3.4% for sulfidity, and 5.1% for total titratable alkali. Process stops that exposed the sensor to temperature excursions or acid washings resulted in temporary periods of poor prediction.

  • 2.
    Bjorklund, Robert
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Magnusson, C.
    Arla Foods.
    Martensson, P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Krantz-Rülcher , Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Continuous monitoring of yoghurt fermentation using a noble metal electrode array2009In: International Journal of Food Science and Technology, ISSN 0950-5423, Vol. 44, no 3, p. 635-640Article in journal (Refereed)
    Abstract [en]

    An electrochemical probe containing gold, platinum and rhodium working electrodes was used to monitor yoghurt production in a pilot facility. Three commercial starting cultures at 40, 42 and 44 C transformed milk having 1.5% fat content to mild yoghurt products. The electrochemical changes in the broth during fermentation were recorded as current responses from pulse voltammetry over the electrodes. Principal component analysis of the responses generated two-dimensional score plots describing the qualitative fermentation progressions. Two distinct fermentation pathways were observed leading to similar final products. The pH was recorded during the fermentations and the data was used as reference values for creating a partial least squares model for prediction of pH as an example of a quantitative application for the sensor. The relative mean squared error for validation of the model using four probes interchangeably was about 2%. The probe was constructed of materials approved for use in the food industry and did not require a standard glass reference electrode.

  • 3.
    Francioso, L.
    et al.
    University Campus, Lecce, Italy.
    Bjorklund, Robert
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcker, Tina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Siciliano, P.
    University Campus, Lecce, Italy.
    Classification of multiple defect concentrations in white wine by platinum microelectrode voltammetry2007In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 125, no 2, p. 462-467Article in journal (Refereed)
    Abstract [en]

    Concentrations of defect pairs added to a white wine were classified by voltammetric measurements on interdigitated platinum microelectrodes using principal component analysis of the current responses. Combinations of 0, 1, 2 and 3 mM concentrations were investigated. The defect pair ascorbic acid/acetaldehyde exhibited little interaction with each other and the pair-wise concentrations were symmetrically positioned in a score plot around a center axis of equimolar concentrations. The ascorbic acid/sulfur dioxide pair exhibited a center axis for the equimolar concentrations shifted toward the 3 mM sulfur dioxide sample. The defect pair having the strongest interaction through complex formation, acetaldehyde/sulfur dioxide, had the equimolar concentrations in score plots located near the white wine control sample. © 2007 Elsevier B.V. All rights reserved.

  • 4.
    Gutes, A.
    et al.
    Gutés, A., Sensors and Biosensors Group, Department of Chemistry, Autonomous University of Barcelona, Edifici Cn, 08193 Bellaterra, Spain.
    Cespedes, F.
    Sensors and Biosensors Group, Department of Chemistry, Autonomous University of Barcelona, Edifici Cn, 08193 Bellaterra, Spain.
    del, Valle M.
    del Valle, M., Sensors and Biosensors Group, Department of Chemistry, Autonomous University of Barcelona, Edifici Cn, 08193 Bellaterra, Spain.
    Louthander, D.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    A flow injection voltammetric electronic tongue applied to paper mill industrial waters2006In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 115, no 1, p. 390-395Article in journal (Refereed)
    Abstract [en]

    A voltammetric electronic tongue with automated operation based on the flow injection (FIA) technique was applied to the characterization of wastewaters coming from the paper mill industry. A metallic multielectrode array - formed by platinum, gold and rhodium electrodes - was employed as the detection system, while the measurements were based on large amplitude pulse voltammetry (LAPV). LAPV consisted in scans of pulses from to 0 to 1.8 V at 0.2 V steps. Five current values were recorded for each pulse, so a set of 300 current values (three electrodes × 20 pulses × five values) was recorded for each sample. Samples were first discriminated using Principal Component Analysis (PCA), while Artificial Neural Networks were used for the characterization and prediction of chemical oxygen demand, conductivity and pH. The system may be used for the quick identification and monitoring of the quality of used waters in these industrial facilities. © 2005 Elsevier B.V. All rights reserved.

  • 5.
    Holmin, Susanne
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Krantz-Rulcker, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Winquist, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Investigation of Electrode Materials as Sensors in a Voltammetric Electronic Tongue2002In: Electroanalysis, ISSN 1040-0397, E-ISSN 1521-4109, Vol. 14, no 12, p. 839-847Article in journal (Refereed)
    Abstract [en]

    In this work different electrode materials were investigated as sensors in a voltammetric electronic tongue. Basically, the electronic tongue is based on the combination of nonspecific sensors (electrodes) and pattern recognition tools, for example principal component analysis (PCA). Copper. glassy carbon, nickel, palladium, silver, tin, titanium and zirconium together with more traditional electrode materials such as gold, iridium, and platinum were studied. Cyclic voitammetry was applied to study typical model reactions in solutions containing different electroactive compounds, like ascorbic acid, glucose, histidine and potassium hexacyanoferrate(II). Different sensitivity and selectivity were obtained with the electrodes. Large responses were for example found for the amino acid and the carbohydrate using the copper, nickel and silver electrode. Some of the electrodes were employed in multicomponent solutions, i.e., liquid washing detergents from different suppliers together with differential pulse voltammetry. Responses from the electrodes in combination with PCA showed that they separated the detergents to different extents. This was further used when information from the sensors was merged together for successful discrimination of the detergents. It was found that two detergents close to each other in the score plot were from the same supplier. Furthermore. scanning electron microscopy (SEM) was used to monitor surface changes at the nonnoble electrodes (copper, nickel, and silver).

  • 6.
    Holmin, Susanne
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Drift correction of electronic tongue responses2001In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 12, no 8, p. 1348-1354Article in journal (Refereed)
    Abstract [en]

    In this article, drift correction algorithms were used in order to remove linear drift in multivariate spaces of two data sets obtained by an electronic tongue based on voltammetry. The electronic tongue consisted of various metal electrodes (Au, Ir, Pt, Rh) combined with pattern recognition tools, such as principal component analysis. The first data set contained different types of liquid, from well defined to more complex solutions. The second data set contained different black and green teas. Component correction (CC) was compared to a simple additive correction. In CC, the drift direction of measured reference solutions in a multivariate space was subtracted from other types of solution. In additive correction, responses from reference samples were subtracted from other samples. CC showed similar or better performance in reducing drift compared to additive correction for the two data sets. The additive correction method was dependent on the fact that the differences in between samples of a reference solution were similar to the changes in between samples of other liquids, which was not the case with CC.

  • 7.
    Holmin, Susanne
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Multivariate optimisation of electrochemically pre-treated electrodes used in a voltammetric electronic tongue2004In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 519, no 1, p. 39-46Article in journal (Refereed)
    Abstract [en]

    The use of experimental design as a tool to optimise electrochemically cleaned electrodes applied in a voltammetric electronic tongue is described. A simple and quick activation of electrode surfaces is essential for this type of device, especially for on-line applications in industrial processes. The electronic tongue consisted of four metal electrodes, e.g. Au, Ir, Pt, and Rh in a three-electrode configuration. Current was measured as a function of large potential pulses of decreasing amplitude applied to each electrode. Preliminary results showed that electrochemical cleaning activated the electrode surfaces to similar extent as polishing. Settings of potential and time for each electrode was determined with experimental design in a solution containing 1.0 mM K 4[Fe(CN)6] in 0.1 M phosphate buffer (pH 6.8). Electrode surfaces were deactivated in-between measurements in a complex liquid, like tea. Optimal settings for potential and time in the electrochemical cleaning procedure at each electrode were chosen at recoveries of 100% (compared to polished electrodes). The recoveries were larger than 100% when too large potentials and times were applied. This could be explained by the fact that the electrode areas increased and therefore also the current responses. Principal component analysis (PCA) was used to investigate the stability of the electrode settings at 100% recoveries. No obvious trends of drift in the signals were found. © 2004 Elsevier B.V. All rights reserved.

  • 8.
    Holmin, Susanne
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Spångéus, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Compression of electronic tongue data based on voltammetry - A comparative study2001In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 76, no 1-3, p. 455-464Conference paper (Other academic)
    Abstract [en]

    In this paper, three data compression methods are investigated to determine their ability to reduce large data sets obtained by a voltammetric electronic tongue without loss of information, since compressed data sets will save data storage and computational time. The electronic tongue is based on a combination of non-specific sensors and pattern recognition tools, such as principal component analysis (PCA). A series of potential pulses of decreasing amplitude are applied to one working electrode at a time and resulting current transients are collected at each potential step. Voltammograms containing up to 8000 variables are subsequently obtained. The methods investigated are wavelet transformation (WT) and hierarchical principal component analysis (HPCA). Also, a new chemical/physical model based on voltammetric theory is developed in order to extract interesting features of the current transients, revealing different information about species in solutions. Two model experiments are performed, one containing solutions of different electroactive compounds and the other containing complex samples, such as juices from fruits and tomatoes. It is shown that WT and HPCA compress the data sets without loss of information, and the chemical/physical model improves the separations slightly. HPCA is able to compress the two data sets to the largest extent, from 8000 to 16 variables. When data sets are scaled to unit variance, the separation ability improves even further for HPCA and the chemical/physical model. © 2001 Elsevier Science B.V.

  • 9.
    Ivarsson, Patrik
    et al.
    Asko Cylinder AB.
    Holmin, Susanne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Hojer, N.-E.
    Höjer, N.-E., Asko Cylinda AB, SE-534 82 Vara, Sweden.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Discrimination of tea by means of a voltammetric electronic tongue and different applied waveforms2001Conference paper (Other academic)
    Abstract [en]

    A new sensor technology, an electronic tongue based on voltammetry has been developed at Linköping University. Three different metallic working electrodes are used in combination with a set of voltage "pulses", a waveform, to separate different samples. In this paper, three different waveforms are investigated. This is done through a study with nine different teas. Multivariate data analysis ((MVDA), principal component analysis (PCA)) is used to evaluate the data (the recorded current responses). The waveforms are large amplitude pulse voltammetry (LAPV), small amplitude pulse voltammetry (SAPV), and staircase voltammetry. Each method discriminated between the tea samples to some extent, but differently from each other. Best discrimination is achieved when the combination LAPV and staircase are merged together. When SAPV is included in the combination a worse separation is observed. It is clearly the case that more waveforms do not automatically lead to more information. © 2001 Elsevier Science B.V.

  • 10.
    Ivarsson, Patrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Faculty of Science & Engineering. Asko Cylinder AB.
    Johansson, Madeleine
    Asko Cylinda AB.
    Höjer, Nils-Erik
    Asko Cylinda AB.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Supervision of rinses in a washing machine by a voltammetric electronic tongue2005In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 108, no 01-Feb, p. 851-857Article in journal (Refereed)
    Abstract [en]

    A study that investigates if it is possible to discriminate between the different rinses in a household washing machine with a voltammetric electronic tongue is concluded. The voltammetric electronic tongue applies a potential pulse train over two electrodes and measures the produced current. Multivariate data analysis is used to treat the data. In this paper, a simplified electronic tongue, with only 5% of the original current responses, is used. The rinses from 20 machine wash runs with four different prerequisites are investigated. Principal component analysis (PCA) and Soft-independent modelling of class analogy (SIMCA) are used in order to classify the rinses. In PCA, only one of the rinses is classified erroneous, and in SIMCA none of the rinses are classified only to the wrong class, although 38% of the rinses are classitied to more than one class. (c) 2005 Elsevier B.V. All rights reserved.

  • 11.
    Ivarsson, Patrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Faculty of Science & Engineering. Asko Cylinder AB.
    Kikkawa, Y.
    Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 812-8581, Japan.
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Hojer, N.-E.
    Höjer, N.-E., Asko Cylinda AB, SE-534 82 Vara, Sweden.
    Hayashi, K.
    Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 812-8581, Japan.
    Toko, K.
    Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 812-8581, Japan.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Comparison of a voltammetric electronic tongue and a lipid membrane taste sensor2001In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 449, no 1-2, p. 59-68Article in journal (Refereed)
    Abstract [en]

    An electronic tongue based on voltammetry and a multichannel lipid membrane taste sensor based on potentiometry are compared using two aqueous examples: detergents and teas. The electronic tongue consists of four electrodes of different metals, a reference electrode and a counter electrode. The measurement principle is based on pulse voltammetry in which current is measured during the change of the amplitude of the applied potential. The taste sensor is based on eight different lipid/polymer membranes. The voltage difference between the electrodes and an Ag/AgCl reference electrode is measured when the current is close to zero. The responses from the two sensors systems are treated separately with multivariate data analysis based on principal component analysis and then merged to examine if further information could be extracted. It is shown that although the two sensor systems are about equal in separation ability in the two cases, extra information can be gained by combination of the two sensor systems. © 2001 Elsevier Science B.V. All rights reserved.

  • 12.
    Ivarsson, Patrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, Faculty of Science & Engineering.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    A voltammetric electronic tongue2005In: Chemical Senses, ISSN 0379-864X, E-ISSN 1464-3553, Vol. 30, p. I258-i259Article in journal (Refereed)
  • 13. Johansson, E.
    et al.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Zhang, B.X.
    Institute of Soil Science, Academica Sinica, Nanjing, China.
    Öberg, Gunilla
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Thematic Studies, Environmental Science.
    Chlorination and biodegradation of lignin2000In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 32, no 7, p. 1029-1032Article in journal (Refereed)
    Abstract [en]

    Recent research has shown that large amounts of high-molecular weight organic chlorine of unknown origin are present in the terrestrial environment. There are indications that an underlying process may be microorganisms which produce reactive chlorine that chemically degrades organic matter and facilitates degradation of recalcitrant organic matter on one hand, and on the other hand causes a formation of organic chlorine. Our aim was to test one part of this hypothesis by investigating whether reactive chlorine facilitates microbial degradation of lignin. Different concentrations of chlorine dioxide were added to the autoclaved lignin suspension. Mycelium of the white-rot fungus P. chrysosporium was used to inoculate flasks with the lignin solutions. The evolution of CO2 was followed during 8 d of continuous measurement. At the end of the experiment the solutions were analyzed for organic chlorine. The amount of CO2 evolved was variable, but the results were repeatedable, addition of chlorine dioxide to the lignin solutions caused an increase in the mineralization by P. chrysosporium that increased with increasing additions of chlorine dioxide. This suggests that exposure of lignin to reactive chlorine enhance its biodegradability. The most likely cause of the observed effect is that the addition of chlorine dioxide initiated a fragmentation and oxidation of the lignin, thus rendering a more easily degraded substrate. However, the results may also be interpreted as if an additional cause to the observed effect is that the chlorination in itself somehow enhanced degradation. The amount of organically-bound chlorine decreased during the incubation, and the decrease was more pronounced with the chlorination of lignin, whereas no change at all was observable in the control batches. This makes it tempting to suggest that P. chrysosporium rather than having an enzyme system just capable of handling the chlorinated compounds, actually has a system that preferentially degrades such compounds. (C) 2000 Elsevier Science Ltd.

  • 14.
    Krantz-Rülcher, Christina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Stenberg, M.
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Electronic tongues for environmental monitoring based on sensor arrays and pattern recognition: A review2001In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 426, no 2, p. 217-226Conference paper (Other academic)
    Abstract [en]

    The use of sensor arrays and pattern recognition applied to the obtained signal patterns for environmental monitoring are discussed in some detail. Different types of electronic tongues are described and evaluated for monitoring purposes. More specifically the performance of multielectrode arrays used for voltammetric analysis of aqueous samples is described. It is, e.g. shown how such an 'electronic tongue' can be used to monitor the quality of water in a production plant for drinking water. It is pointed out that the concepts of 'electronic noses' and 'electronic tongues' often predict a quality of a sample rather than giving exact information about concentrations of individual species. (C) 2001 Elsevier Science B.V.

  • 15.
    Krantz-Rülcker, Tina
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Effects of fungi on the distribution of metals in soil systems1993Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fungal biomass has previously been shown to be an effective adsorbent for recovery of metals from heavily polluted wastes and waters. Most studies of metal accumulation properties by fungi have therefore been performed at high metal concentrations and using preconditioned fungal biomass. Since fungi constitute, the 'largest group of microbial organisms in soil, on a weight basis, and, as indicated possess a high metal-accumulating capacity, they should indeed be considered to be important metal adsorbents. The aim of the present study was to improve the understanding of the impact of fungi on the mobility of trace metals in natural soil systems. Experimental work was therefore conducted under chemical and biological conditions relevant in uncontaminated soils.

    Three different soil fungi (Mortierella isabellina, Penicillium spinulosum and Trichoderma harzianum) were selected. They all showed a considerable ability to accumulate IIb metals (Zn, Cd and Hg). The accumulation by starved mycelia had a limited pH dependence at low metal concentrations, while non-starved mycelia showed an increased accumulation at low pH. This increase appeared to be related to a production of hydrophilic organic compounds. The high ability to accumulate metals at low pH can be explained by the existence of metal-specific sites in the fungal cell walls.

    Calculations of the hypothetical distribution of a divalent cationic element in a model soil system indicated the potential importance of fungal metal accumulation in soils. Due to the specific accumulation of metals by the fungi at low pH the fraction associated to the fungal biomass could be considerable and in some cases predominant. A multi compartment system was constructed to corroborate these calculations. This design wasfound to be of great value for simultaneous de terminations of metal partitioning between different soil constituents present in relevant proportions. The results from this system closly resembled the hypothetical calculations.

    The accumulation of metals by fungi leading to higher metal concentrations in association with the fungal biomass had an impact on the degradability of the mycelia. A considerable inhibition of this degradation was observed under certain conditions.

    The general conclusion of this thesis is that fungi constitute an important soil component for the partitioning of trace metals between stationary and mobile forms. In particular, acidification of soils must be considered in perspective of the qualitative features of the accumulation processes.

  • 16. Ledin, Maria
    et al.
    Krantz-Rülcker, Tina
    Linköping University, Faculty of Arts and Sciences. Linköping University, The Tema Institute.
    Allard, Bert
    Microorganisms as metal sorbents: comparison with other soil constituents in multi-compartment systems1999In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 31, no 12, p. 1639-1648Article in journal (Refereed)
  • 17.
    Lundström, Ingemar
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Sundgren, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Eriksson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcker, Tina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Twenty-five years of field effect gas sensor research in Linköping2007In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 121, no 1, p. 247-262Article in journal (Refereed)
    Abstract [en]

    The present contribution contains an overview of the development of gas sensitive field-effect devices in Linköping during the last 25 years. It is completely centred to the work at the Laboratory of Applied Physics at Linköping University, and is therefore not a proper review of a research field where many important contributions have been made by several other research groups. © 2006 Elsevier B.V. All rights reserved.

  • 18.
    Söderström, Charlotte
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Borén, Hans
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Use of an electronic tongue and HPLC with electrochemical detection to differentiate molds in culture media2005In: International Journal of Food Microbiology, ISSN 0168-1605, E-ISSN 1879-3460, Vol. 97, no 3, p. 247-257Article in journal (Refereed)
    Abstract [en]

    A study was conducted to further evaluate an electronic tongue, using high-performance liquid chromatography (HPLC) with electrochemical (EC) and UV detection as a reference method. The electronic tongue consisted of four working electrodes made of different metals and arranged in a standard three-electrode configuration. Pulses of voltage were applied to the metals, and the current responses were sampled and collected in a data matrix. The objectives of the present investigation were to examine the ability of the electronic tongue to distinguish between two mold species growing in three different media, and to obtain support for the hypothesis that the device actually discriminates between different redox-active metabolites produced by the molds. Peak areas in EC and UV HPLC chromatograms were collected in a data matrix. The electronic tongue data and the EC and UV data were then subjected to principal component analysis (PCA). A number of peaks in the HPLC-EC chromatograms indicated that the growth media contained redox-active metabolites. Moreover, PCA of peak areas in EC chromatograms revealed differences between the distribution of redox-active metabolites produced by the two species and between the three culture media. The same pattern was apparent in a PCA score plot of electronic tongue data. The peaks in the UV and EC chromatograms differed, and these were also shown by the PCA score plots.

  • 19.
    Söderström, Charlotte
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Borén, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Organic Analytical Chemistry .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Use of an electronic tongue to analyze mold growth in liquid media2003In: International Journal of Food Microbiology, ISSN 0168-1605, E-ISSN 1879-3460, Vol. 83, no 3, p. 253-261Article in journal (Refereed)
    Abstract [en]

    The feasibility of employing an electronic tongue to measure the growth of mold in a liquid medium was studied. We used the electronic tongue developed at Linköping University, which is based on pulsed voltammetry and consists of an array of different metal electrodes. Instead of focusing on a single parameter, this device provides information about the condition or quality of a sample or process. Accordingly, the data obtained are complex, and multivariate methods such as principal component analysis (PCA) or projection to latent structures (PLS) are required to extract relevant information. A gas chromatographic technique was developed to measure ergosterol content in mold biomass and was subsequently used as a reference method to investigate the ability of the electronic tongue to measure the growth of mold in liquid media. The result shows that the electronic tongue can monitor mold growth in liquids. In PLS analysis, the electronic tongue signals correlate well with the amount of ergosterol in the mold biomass as well as the microbially induced changes in the pH of the medium. © 2002 Elsevier Science B.V. All rights reserved.

  • 20.
    Söderström, Charlotte
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Rudnitskaya, A.
    Chemistry Dept St. Petersburg University.
    Legin, A.
    Chemistry Dept. St. Petersburg University.
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Differentiation of four Aspergillus species and one Zygosaccharomyces with two electronic tongues based on different measurement techniques2005In: Journal of Biotechnology, ISSN 0168-1656, E-ISSN 1873-4863, Vol. 119, no 3, p. 300-308Article in journal (Refereed)
    Abstract [en]

    Two electronic tongues based on different measurement techniques were applied to the discrimination of four molds and one yeast. Chosen microorganisms were different species of Aspergillus and yeast specie Zygosaccharomyces bailii, which are known as food contaminants. The electronic tongue developed in Linköping University was based on voltammetry. Four working electrodes made of noble metals were used in a standard three-electrode configuration in this case. The St. Petersburg electronic tongue consisted of 27 potentiometric chemical sensors with enhanced cross-sensitivity. Sensors with chalcogenide glass and plasticized PVC membranes were used. Two sets of samples were measured using both electronic tongues. Firstly, broths were measured in which either one of the molds or the yeast grew until late logarithmic phase or border of the stationary phase. Broths inoculated by either one of molds or the yeast was measured at five different times during microorganism growth. Data were evaluated using principal component analysis (PCA), partial least square regression (PLS) and linear discriminant analysis (LDA). It was found that both measurement techniques could differentiate between fungi species. Merged data from both electronic tongues improved differentiation of the samples in selected cases. © 2005 Elsevier B.V. All rights reserved.

  • 21.
    Söderström, Charlotte
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Winquist, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Recognition of six microbial species with an electronic tongue2003In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 89, no 3, p. 248-255Article in journal (Refereed)
    Abstract [en]

    An electronic tongue based on pulsed voltammetry over an array of electrodes with different selectivity and sensitivity patterns was used to recognize six different microorganisms: one yeast, two bacteria, and three molds. Measurements were performed during the whole growth period, from the lag phase to the stationary phase. The electrode array was dipped into the malt extract growth medium and voltage was applied over the electrodes in pulses of different amplitude and the resulting current data was sampled and collected in a matrix. Evaluation of the electronic tongue data was made with principal component analysis (PCA) and soft independent modeling of class analogy (SIMCA). PCA was performed on data from the lag, the logarithmic, and also the stationary growth phase. In the lag growth phase no recognition of species was visible in the PCA score plots. After further growth however all the included microbial species could be recognized from each other. The ability to predict membership of new replicates of the species to the right classes was verified with SIMCA. © 2003 Elsevier Science B.V. All rights reserved.

  • 22.
    Ulrich, Christian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Petersson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Sundgren, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Björefors, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Krantz-Rülcker, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Simultaneous estimation of soot and diesel contamination in engine oil using electrochemical impedance spectroscopy2007In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 127, no 2, p. 613-618Article in journal (Refereed)
    Abstract [en]

    In this paper, we explore the combination of electrochemical impedance spectroscopy and multivariate data analysis to simultaneously predict the concentrations of soot and diesel in engine oil. For this purpose, we use a well defined measurement set-up to minimize interference from ambient noise, and to obtain a large amount of data in a short period of time. An imperative requirement is that soot and diesel affect the impedance in different ways over the employed frequency range. It was, for example, found that diesel had a larger influence at lower frequencies. Using partial least squares modelling we show that it is possible to simultaneously predict the concentrations of both soot and diesel in engine oil. Since the temperature in an engine varies, the influence of the oil temperature is investigated in a preliminary experiment. This study is a part of the development of an electrochemical on-board sensor for real-time monitoring of engine oil.

  • 23.
    Winquist, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Bjorklund, Robert
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Ostergren, K
    Skoglund, T
    An electronic tongue in the dairy industry2005In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 111, p. 299-304Article in journal (Refereed)
    Abstract [en]

    The concept of electronic tongues or taste sensors has developed rapidly during recent years due to their large potential. They are based on electrochemical sensors combined with multivariate data analysis. Voltammetric electronic tongues have proven valuable in many applications. Due to their ruggedness and simplicity, they have been found especially suitable for on-line monitoring of industrial processes. A voltammetric electronic tongue, specially designed for use in the dairy industry is described. It consisted of four working electrodes (gold, platinum, rhodium and stainless steel), embedded in PEEK (TM). It was mounted in a housing of stainless steel, which was inserted in the process line for direct on-line measurements. The voltammetric electronic tongue was used to follow different sources of milk coming into the process and to monitor the cleaning process. (c) 2005 Elsevier B.V. All rights reserved.

  • 24.
    Winquist, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Holmin, Susanne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Wide, Peter
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Pediatrics . Östergötlands Läns Landsting, Centre of Paediatrics and Gynecology and Obstetrics, Department of Paediatrics in Linköping.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    A hybrid electronic tongue2000In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 406, no 2, p. 147-157Article in journal (Refereed)
    Abstract [en]

    A hybrid electronic tongue is described based on a combination of potentiometry, voltammetry and conductivity. It was used for classification of six different types of fermented milk. Using ion-selective electrodes, pH, carbon dioxide and chloride ion concentrations were measured. The voltammetric electronic tongue consisted of six working electrodes of different metals (gold, iridium, palladium, platinum, rhenium and rhodium) and an Ag/AgCl reference electrode. The measurement principle is based on pulse voltammetry in which current transients are measured due to the onset of voltage pulses at decreasing potentials. The data obtained from the measurements were treated by multivariate data processing based on principal components analysis and an artificial neural net. The hybrid tongue could separate all six samples. Also, the nature of the micro-organisms in the different fermentations was reflected in the principal component analysis. Copyright (C) 2000 Elsevier Science B.V.

  • 25.
    Winquist, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    A miniaturized voltammetric electronic tongue2008In: Analytical Letters, ISSN 0003-2719, E-ISSN 1532-236X, Vol. 41, no 5, p. 917-924Article in journal (Refereed)
    Abstract [en]

    A miniaturized electronic tongue based on pulsed voltammetry has been developed. It was made by inserting three types of wires acting as working electrodes (gold, platinum, and rhodium, diameter 0.25 mm) into a platinum tube acting as a counter electrode (diameter 2 mm, length 4 mm). The arrangement was connected to a potentiostat controlled by a computer. Due to the small size of the miniaturized electronic tongue, and since no reference electrode is used, the setup is very simple and convenient. In order to characterize the analytical possibilities of the miniaturized electronic tongue, some initial experiments were performed. These include the determination of trace amounts of cadmium and lead (in the µM range) in 5 µL samples. Furthermore, the setup was placed under the real tongue of a volunteer to follow saliva composition during exercise. Copyright © Taylor & Francis Group, LLC.

  • 26.
    Winquist, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Electronic tongues2004In: MRS bulletin, ISSN 0883-7694, E-ISSN 1938-1425, Vol. 29, no 10, p. 726-731Article in journal (Refereed)
    Abstract [en]

    The use of multivariate data analysis combined with sensors with partially overlapping selectivities has become a very powerful tool in measurement technology. These systems are often referred to as artificial senses, because they function in a way similar to the human senses. One such system is the electronic nose. This article focuses on similar concepts as the electronic nose, but for use in aqueous solutions. Because these systems are related to the human sense of taste in the same way the electronic nose is related to olfaction, they have been termed taste sensors, or "electronic tongues." Various measurement principles that can be used in electronic tongues are described and discussed in this article, These include electrochemical techniques such as potentiometry, voltammetry, and conductometry. Also, optical techniques based on light absorption at specific wavelengths or the use of surface plasmon resonance are described. Mass-sensitive devices based on piezoelectric crystals have also been used and are described here. A special emphasis is given to the voltammetric electronic tongue.

  • 27.
    Winquist, Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Krantz-Rülcher, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Olsson, Thomas
    Lantmannen Analycen.
    Jonsson , Anders
    University of Agriculture Science, Sweden.
    Measurements of cadmium in soil extracts using multi-variate data analysis and electrochemical sensors2009In: PRECISION AGRICULTURE, ISSN 1385-2256 , Vol. 10, no 3, p. 231-246Article in journal (Refereed)
    Abstract [en]

    There is a growing awareness of potential health risks due to exposure to heavy metals. One source of uptake is via agriculture, when heavy metals in the soil are taken up by the crop. The metal cadmium holds a special position, since it is considered to be a health risk, even at the low concentrations observed in our food supply, furthermore, it is ranked as eight on the top 20 hazardous substances list. Two measurement systems are described based on stripping voltammetry for analysis of cadmium. One is based on a three metal direct probe system (TMDPS) with three working electrodes (platinum, gold and rhodium), combined with a polishing unit, the other is an automatic flow through system, using one working electrode of gold, also equipped with a polishing unit. A number of different soils were extracted with an ammonium-lactate solution and analyzed with the systems, and the data obtained were subjected to multi-variate data analysis (MVDA). Using modeling based on partial least square (PLS), concentrations of cadmium in the soil extracts could be predicted for the TMDPS in the concentration area 0.5-10 mu g/l with a root mean square error of prediction (RMSEP) of 0.8 mu g/l and a relative predicted deviation (RPV) of 2.0. One sample could be analyzed in 4 min. It was also shown that by using different PLS models, the concentration of the elements copper, aluminum, lead and iron could be predicted. The possibilities of using the technique for field use were also evaluated by studies of mixtures of different soils in 0.1 M HNO3 solution, the time for an analysis was, however, rather large, around 20 min.

  • 28.
    Winquist, Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Rydberg, Elinor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Holmin, Susanne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Krantz-Rülcher, Christina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Flow injection analysis applied to a voltammetric electronic tongue2002In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 471, no 2, p. 159-172Article in journal (Refereed)
    Abstract [en]

    A measurement system, based on flow injection analysis (FIA) technique applied to a voltammetric electronic tongue is described. A reference solution was thus continuously pumped through a cell with a voltammetric electronic tongue, and test samples were injected into the flow stream. Responses were obtained by measuring the resulting pulse height. The FIA technique offered several advantages, since relative measurements are performed, the system is less influenced by sensor baseline drift, calibration samples and/or washing solutions can be injected within a measurement series, and the system is well adapted for automatization. The system was used to analyze standard solutions of H2O2, KCl, CuNO3, K4[Fe(CN)6], K3[Fe(CN)6] and NaCl, and results obtained were treated with multivariate data analysis. Principal component analysis performed showed that electrode drift could be considerably decreased, and the set-up was also used for classification of different apple juices. © 2002 Elsevier Science B.V. All rights reserved.

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