An FIA system capable of the direct and simultaneous determination of ascorbic acid and glucose in commercial soft drinks is described. The system features a flow-through electrolysis cell ...(electrochemical filter, ECF) for a coulometric determination based on the quantitative electrolysis of ascorbic acid and a glucose oxidase monolayer electrode for the amperometric determination of glucose. Although ascorbic acid interferes with the glucose biosensor, quantitative electrooxidation in the ECF supresses the error. The glucose biosensor did not exhibit saturation for 0.1 M-order glucose samples. The measured values for nine commercial soft drinks without any pretreatment, such as dilution, showed a good correlation to those determined with conventional methods.
Real-time process monitoring is still relatively scarce but is fundamental to provide in-situ information about different chemical and electrochemical processes. Particularly, electrochemical ...filtration has received growing attention in recent years due to the wide range of applications in which it can be successfully employed. Electrochemical removal is considered as an attractive methodology for the treatment of wastewater due to its efficiency in the removal of a huge number of contaminants. In this work, the development of a new device based on the use of UV–vis bare optical fibers in long optical pathway configuration allows us to monitor continuously the electrochemical degradation process during the filtration of different compounds. Spectroelectrochemistry additionally supplies quantitative information allowing us to calculate the efficiency of the electrochemical filtration process. The material selected to fabricate the electrochemical filter was single-walled carbon nanotubes that display not only high physical and chemical stability, but also high electrical conductivity. Therefore, the combination of electrochemical degradation methods, free-standing single-walled carbon nanotube filters and operando spectroelectrochemical techniques makes this outstanding device very interesting in the study of different molecules. As proof of concept, three different systems have been studied to validate the cell and demonstrate the good performance of the spectroelectrochemical device: o-tolidine (reference system), indigo carmine (organic dye), and 4-nitrophenol (hazardous pollutant).
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Theoretical predictions on sensor performance are compared with experimental data obtained for YSZ (yttria stabilized zirconia) sensors protected by different types of single phase mixed conductors, ...including materials usually identified as predominantly ionic or electronic conductors. Relevant parameters determining the protected sensor performance are the ratio between the sensor and the filter oxygen electrochemical permeabilities, the volume of the electrode protection chamber, the temperature and the magnitude of the oxygen pressure being measured. The sensor to filter electrochemical permeability ratio determines the steady state deviation between the protected and unprotected sensor reading. Decreasing the protected chamber volume and the magnitude of the oxygen partial pressure being measured will determine a faster sensor response. Results now reported, corresponding mostly to slow sensor response, are strongly determined by the relatively low operating temperatures (850–950 °C) used in these laboratory scale experiments, but can be optimized for industrial applications.
This work reports on the performance of YSZ oxygen sensors protected by “electrochemical filters” based on ionic conductors under external short circuit, or composite materials including one ionic ...and one electronic conductor. In both cases it is assumed that the electronic conductor will provide the pathway for electrons or electron holes while the ionic conductor provides the pathway for oxygen ions. These solutions were envisaged to overcome the limited performance of single phase mixed conducting filters which exhibit relatively low electrochemical permeabilities. A simplified model has been derived to relate the steady state and transient behavior of these devices to the most relevant system and materials parameters determining the sensor performance. Theoretical predictions are compared with experimental data obtained with different types of materials combinations and qualitative agreement is found between predicted and effective role of different parameters on protected sensor performance. In these concepts the sensor transient response depends strongly on the ionic resistance of the filter, although for high temperatures this will become negligible and identical to the electronic component.
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