Dual carbon cell

FIGURE 12.13 A schematic illustration of the charge/discharge mechanism for the dual carbon cells by FDK Co. (From http //www.fdk.co.jp/cyber-j/pi technical08.html.)... 

Detector E, ESA Coulochem II, Model 5011 dual analytical cell, upstream +0.65 V, downstream +0.85 V (monitored), analytical cell protected by an ESA carbon in-line filter... 

Detector E, ESA Coulochem Model 5100A, Model 5020 guard cell 1.0 V (before iiyector), Model 5010 dual-electrode cell, screen electrode El -I- 0.7 V, sample electrode E2 -t-O.O V, 0.5 j,m ESA carbon filters placed before guard and analytical cells... 

Precipita.tingInhibitors. As discussed earlier, the localized pH at the cathode of the corrosion cell is elevated due to the generation of hydroxide ions. Precipitating inhibitors form complexes that are insoluble at this high pH (1—2 pH units above bulk water), but whose deposition can be controlled at the bulk water pH (typically 7—9 pH). A good example is zinc, which can precipitate as hydroxide, carbonate, or phosphate. Calcium carbonate and calcium orthophosphate are also precipitating inhibitors. Orthophosphate thus exhibits a dual mechanism, acting as both an anodic passivator and a cathodic precipitator. 

A dual isotope labeling technique [85] has been used to measure membrane permeability in plant cells, based on the selective permeabiHty of the membranes of living cells to tritiated water and carbon-14 labeled mannitol. Kieran [29] showed that the results of the dual isotope labeling and Evan s Blue staining methods correlated well as indicators of cell viability however, the latter was preferable in terms of reagent cost and ease of analysis. 

Aniline, methyl aniline, 1-naphthylamine, and diphenylamine at trace levels were determined using this technique and electrochemical detection. Two electrochemical detectors (a thin-layer, dual glassy-carbon electrode cell and a dual porous electrode system) were compared. The electrochemical behavior of the compounds was investigated using hydrodynamic and cyclic voltammetry. Detection limits of 15 and 1.5nmol/l were achieved using colourimetric and amperometric cells, respectively, when using an in-line preconcentration step. 

Acetylene black is the carbon material of choice for the cathode of Leclanche cells. Acetylene black serves a dual purpose (1) it provides a conducting path between the carbon rod current collector and the particle of active Mn02 material and (2) it absorbs and holds, or retains, the electrolyte for ionic conductivity throughout the cathode structure. Carbons, used as the conductive diluent, do not participate in the redox reactions that generate current and voltage. 

Jusys, Z. and Behm, R.J., Simulated air bleed oxidation of adsorbed CO on carbon supported Pt. Part 2. Electrochemical measurements of hydrogen peroxide formation during O2 reduction in a double-disk electrode dual thin-layer flow cell, J. Phys. Chem. B, 108, 7893, 2004. 

Even before the introduction of miniaturized biosensor arrays, however, some systems able to simultaneously measure glucose and lactate had been reported in the literature. One example is provided by Osborne et al. [157], who described plastic film carbon electrodes fabricated in a split-disk configuration and then modified to obtain a dual biosensor. They achieved a continuous monitoring of these metabolites by placing the dual electrode in a thin-layer radial flow cell coupled to a microdialysis probe. The stability of the sensors was sufficient for short-term in vivo experiments in which the crosstalk, i.e., the percentage of current measured by one biosensor but due to product generated by the partner biosensor, was acceptable for an in vivo application. 

Glucose and lactate were simultaneously monitored by Wei Min et al. [191] during the fermentation of Lactococcus lactis. They made use of a microdialysis probe connected to a dual flow-through cell in which two amperometric biosensors were located. The biosensors were based on the co-immobilization of the respective oxidase enzymes together with HRP in a carbon paste matrix. Both analytes were monitored on-hne for about 14 h in a very complex aqueous two-phase fermentation process, and the results were in good agreement with independent ofiF-line HPLC measurements. 

Detector E, ESA 5100A Coulochem, ESA 5020 guard cell +1 V, ESA 5010 dual electrode analytical cell, screen electrode +0.7 V, detector electrode +0.8 V, porous carbon electrodes... 

---