Electrochemical cell, flow-through

Fig. 10. Flow-through electrochemical cell designs. I, Planar geometries, thin-layer (A) and wall-jet (B) flow cell designs. II, Cylindrical geometries, open tubular (A), wire in a capillary (B), and packed-bed (C) flow cell designs...

We demonstrated an electroanalytical protocol for the multi-ampero-metric sensing of astringency in tea beverages. The new design of the flow-through electrochemical cell let to accommodate into a channel up... 

Electrochemical cells (general aspects) — Electrochemical cells consist of at least two electron conductors (usually metals) in contact with ionic conductors (-> electrolytes). The current flow through electrochemical cells maybe zero or non-zero. Electrochemical cells... 

Fig. 4 The flow-through electrochemical cell for potentiometric measurements at temperatures up to 400°C A - flow-through Ptfhh) electrode, B - flow-through YSZ(Hg/HgO), C -flow-through external Ag/AgCl reference electrode [13, 16].

Other workers24 have used similar principles to enable continuous production of conducting polymer libers in a flow-through electrochemical cell. As with the hydrodynamic system described in the preceding text, polymer is produced at the anode and continuously removed from the cell in the form of a fiber. Alternatively, other fibers such as Kevlar or nylon can be coated using such hydrodynamically controlled polymerization systems. 

Thus, various chlorinated aliphatic and aromatic compounds were dechlorinated in a flow-through electrochemical cell with a graphite fibre cathode, a Nafion (cation-permeable) membrane and a Pt gauze anode. The concentration of pentachlorophenol decreased from 50 to about 1 mg per litre after 20 min of electrolysis at a current efficiency of about 1 %, and the product was phenol. Similar results were obtained with other chlorode-rivatives. The expected total costs of the process are of the order of 10 DM per 1 m of waste water, which is comparable with the cost of adsorption on active carbon [42]. 

Numerous treatability studies have been performed in small electrochemical batch reactors [13-15]. A typical batch reactor has a rotating cylinder anode (RCA) that is operated well below the limiting current for Ag(II) generation (Figure 4). The RCA enables the scientist or engineer to use a small apparatus to mimic mass-transport conditions in a pilot plant, without using massive flow-through electrochemical cells and pumps. 

Fig. 2. Flow-through electrochemical cell with dropping mercury electrode, suitable for HPLC. The cavity around drop has dimensions of 1 mm.

As in the previous work, the flow injection system consisted of a Cole Parmer Mas-terflex peristaltic pump, Rheodyne 7125 injector, Bioanalytical System (BAS) TL-5A flow through electrochemical cell and either an IBM EC/230 or a BAS CV 37 potentiostat. These instruments respectively are designed for use with an electrochemical detector for liquid chromatography and for low current measurements such as with ultramicroelectrodes. A pulse dampener was also included in the flow system. 

The testing system consisted of a carrier, a syringe pump, a sample injection valve, and a laboratoiy-built flow-through electrochemical cell (Figure 8). The cell was constructed by sandwiching an SPE between a plastic base and a plastic cover outfitted with inlet and outlet holes. A Teflon gasket with a flow channel was mounted between the SPE and the cover to form a flow cell, in which the SPE was exposed to the cell for the electrochemical detection. 

Figure4.5 The most common flow-through electrochemical cell configurations are as follows (A) thin-layer, (B) wall-jet, (C) tubular, (D) porous. The direction of fluid flow is...

B. Godlewska-Zylkiewicz and M. Zaleska. Preconcentration of palladium in a flow-through electrochemical cell for determination by graphite furnace atomic absorption spectrometry. Analytica Chimica Acta 462 305-312, 2002. 

FIGURE 31.12 Schematic representation of the flow-through electrochemical cell used for online generation of the c(ABTS ) 1, anode compartment 2, cathode compartment WE, working electrode RE, reference electrode CE, counter electrode M, Nafion membrane. (Adapted from Ivekovic, D. et al. 2005. Analyst 130 708-714.)... 

Figure 17. Schematic of flow-through electrochemical cell. Reprinted from Ref. 64, Copyright (1997) with permission from Elsevier.

In our own laboratories,we have used the fact the polymerization occurs in solution to develop a flow-through electrochemical cell to produce colloids i or water soluble conducting electroactive polymers (CEPs) continuously. The use of a highly porous anode (reticulated vitreous carbon — RVC) ensures that a high-surface area is available for electropolymerization and that a flowing solution can be used to prevent polymer deposition. The use of steric stabilizers (such as polyethylene oxide or polyvinylalcohol) in the flow-through electrolyte (see use of stabilizers under Chemical Polymerization) also helps prevent deposition and promote colloid formation. Both polypyrrole and polyaniline colloids have been prepared using this approach. 

Recording of voltammograms in the flow-through electrochemical cell, after chromatographic separation, gave the expected results. That is, a M(dtc>2 oxidation response appeared at the retention volume of the complex. 

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