Flow through electrode, carbons

It is also possible to employ detectors with solutions flowing over a static mercury drop electrode or a carbon fiber microelectrode, or to use flow-through electrodes, with the electrode simply an open tube or porous matrix. The latter can offer complete electrolysis, namely, coulometric detection. The extremely small dimensions of ultramicroelectrodes (discussed in Section 4.5.4) offer the advantages of flow-rate independence (and hence a low noise level) and operation in nonconductive mobile phases (such as those of normal-phase chromatography or supercritical fluid chromatography). 

A. N. Strohl and D. J. Curran, Flow Injection Analysis with Reticulated Vitreous Carbon Flow-Through Electrodes. Anal. Chem., 51 (1979) 1045. 

The reagent, Ru(bpy)3 +, is not stable in aqueous solution for extended time, so it is generated externally by oxidation of Ru(bpy)3 [Eq. (17)]. A high-efficiency (>99%) flow-through electrode containing carbon powder as working electrode material is employed for this purpose. The Ru(bpy)3 + solution is then mixed with the mobile phase downstream of the column where Eq. (18) occurs. Ru(bpy)3 " is a strong oxidant (E = +1.24 V vs. NHE) and is able to oxidize both tyrosine and... 

C Reticulated vitreous carbon flow-through electrode as detector No data 24 1-2 Pharmaceuticals 1979 153 ... 

In the Zn/Ch battery, carbon is utihzed in both electrodes, serving as a flow-through positive electrode and a substrate for the zinc negative electrode. The requirements are listed below. Chlorine, flow-through electrode ... 

FIGURE 54 A schematic of hie flow-through immunosensor equipped with (1) fluid inlet, (2) carbon current collector, (3) disposable immuno-column, (4) highly dispersed antibody-modified carbon particles (immunosorbent), (5) carbon counter electrode, (6) Ag AgCl reference electrode and (7) fluid outlet. (Reprinted from [16] with permission from Elsevier.)... 

The use of porous carbon electrodes allows accurate control of the ratio of oxidized and reduced forms of p-nitriline by adjusting the electrolyte flow through the electrode. As a result, the reduction of p-nitraniline to p-phenylenediamine was carried out continuously at current densities three-fold greater than the current densities obtained from batch processes [34] and -45 % of the total yield was obtained, depending on the p-nitriline used [34]. 

As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li = Li+ + e, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon... 

The electrodes in the hydrogen-oxygen cell are porous carbon rods that contain a platinum catalyst. The electrolyte is a hot (several hundred degrees) potassium hydroxide solution. Hydrogen is oxidized at the anode where the hydrogen and hydroxide ions combine to form water. Electrons flow through the external circuit. 

Recently flow coulometry, which uses a column electrode for rapid electrolysis, has become popular [21]. In this method, as shown in Fig. 5.34, the cell has a columnar working electrode that is filled with a carbon fiber or carbon powder and the solution of the supporting electrolyte flows through it. If an analyte is injected from the sample inlet, it enters the column and is quantitatively electrolyzed during its stay in the column. From the peak that appears in the current-time curve, the quantity of electricity is measured to determine the analyte. Because the electrolysis in the column electrode is complete in less than 1 s, this method is convenient for repeated measurements and is often used in coulometric detection in liquid chromatography and flow injection analyses. Besides its use in flow coulometry, the column electrode is very versatile. This versatility can be expanded even more by connecting two (or more) of the column electrodes in series or in parallel. The column electrodes are used in a variety of ways in non-aqueous solutions, as described in Chapter 9. 

In order to determine the number of electrons, the flow-coulometric method described in Section 5.6.3 is also useful. The solution of the supporting electrolyte is flowing through the column-type cell for rapid electrolysis (Fig. 5.34) and the potential of the carbon fiber working electrode is kept at a value at which the de-... 

Voltammetry has been adapted to HPLC (when the mobile phase is conducting) and capillary electrophoresis (CE) as a detection technique for electroactive compounds. In this usage, the voltammetric cell has to be miniaturised (to about 1 pi) in order not to dilute the analytes after separation. A metal or carbon microelectrode has a defined potential (vs the reference electrode) depending on the substances to be detected (ions or molecules) and the mobile phase flows through the detection cell (Fig. 19.5). This method of amperometric detection in the pulsed mode is very... 

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