Electrochemical flow cell design

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...

Fluorescence detection, because of the limited number of molecules that fluoresce under specific excitation and emission wavelengths, is a reasonable alternative if the analyte fluoresces. Likewise, amperometric detection can provide greater selectivity and very good sensitivity if the analyte is readily electrochemically oxidized or reduced. Brunt (37) recently reviewed a wide variety of electrochemical detectors for HPLC. Bulk-property detectors (i.e., conductometric and capacitance detectors) and solute-property detectors (i.e., amperometric, coulo-metric, polarographic, and potentiometric detectors) were discussed. Many flow-cell designs were diagrammed, and commercial systems were discussed. 

The design of the electrochemical flow cell can dramatically affect the performance of the detector. For this reason, several different cell designs have been... 

Parallel-plate flow cells Most electrochemical flow cells are based on a parallel-plate electrode design with either horizontal or, more commonly, vertical electrodes in a monopolar or bipolar configuration (see Figure 26.12). With vertical electrodes, the cell is usually constructed in a plate-and-frame arrangement and mounted on a filter press. 

Instrumentation. A cell design employing reticulated vitreous carbon as the working electrode material that enables both UV-Vis absorption and luminescence measurements has been described [47]. A thin-layer cell with a platinum working electrode has been developed [69]. The luminescence of the electrooxidation products of o-tolidine as a function of electrode potential was studied. A simplified flow cell design has been reported [70]. Luminescence spectra and fluorescence intensity for various aromatic compounds and their electrochemical and photochemical reaction products were observed as a function of flow rate, current and time after the potential step. In the latter study the electrooxidation of p-phenylenediamine (PPD) was examined. The cyclic voltammogram showed two oxidation peaks the first one is assumed to be caused by the formation of the radical cation according to... 

Figure 1 is a schematic diagram of a basic electrochemical flow-deposition system used for electrodepositing thin films using EC-ALE, and Fig. 2 is a picture showing the solution reservoirs, pumps, valves, electrochemical cell, potentiostat, and computer. A number of elechochemical cell designs have been tried. A larger thin-layer electrochemical flow cell is now used (Fig. 3c) [40], with a deposition area of about 2.5 cm and a cell volume of 0.1 mL, resulting in a two order of magnitude drop in solution volume, compared with the H-cell (Fig. 3b). The cell includes an indium tin oxide (ITO) auxiliary electrode, as the opposite wall of the cell from...

Electron paramagnetic resonance (EPR) spectroscopy has also been coupled with electrochemical measurements where radical species are involved in the electrochemical reactions. Figure 2.18 shows a cell for simultaneous electrochanical-EPR studies. The EPR measurements can be ex situ where the radicals are formed outside of the spectrometer (Figure 2.19). In addition, in combination with the flow cell design described above, one can also use electrochanical-EPR technique to monitor the generation of free radicals in a continuous stream of solutions (Figure 2.20). 

Fig. 23.6 Gaskets designed by BASi for electrochemical flow cell, with permission from BASi Bioanalytical Systems, Inc. Further reproduction prohibited without permission. Copyright 2014...

Reaction Engineering. Electrochemical reaction engineering considers the performance of the overall cell design ia carrying out a reaction. The joining of electrode kinetics with the physical environment of the reaction provides a description of the reaction system. Both the electrode configuration and the reactant flow patterns are taken iato account. More ia-depth treatments of this topic are available (8,9,10,12). 

Flow through electrochemical detectors based on a cylindrical geometry, as opposed to a planar geometry, have also been developed Three cell designs using cy-... 

Fig. 3. Diagrams of electrochemical cells used in flow systems for thin film deposition by EC-ALE. A) First small thin layer flow cell (modeled after electrochemical liquid chromatography detectors). A gasket defined the area where the deposition was performed, and solutions were pumped in and out though the top plate. Reproduced by permission from ref. [ 110]. B) H-cell design where the samples were suspended in the solutions, and solutions were filled and drained from below. Reproduced by permission from ref. [111]. C) Larger thin layer flow cell. This is very similar to that shown in 3A, except that the deposition area is larger and laminar flow is easier to develop because of the solution inlet and outlet designs. In addition, the opposite wall of the cell is a piece of ITO, used as the auxiliary electrode. It is transparent so the deposit can be monitored visually, and it provides an excellent current distribution. The reference electrode is incorporated right in the cell, as well. Adapted from ref. [113],...

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