Column electrode cell, rapid electrolysis

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. 

Fig. 5.34 A column electrode cell for rapid electrolysis. WE working electrode of carbon fiber or carbon powder RE reference electrode CE Pt counter electrode.

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-... 

We found that conventional electrolysis (of the partially-neutralised salt) in methanol produced a very rapid increase in applied cell-voltage and the attainment of no effective product (Column I). This was due to the production of a pale coloured coating at the anode which caused the reaction to cease. This is a well known occurrence in electro-organic chemistry [61] and the remedy is to add pyridine to keep the electrode dean, presumably by solubilising the inhibiting layer. Column II shows the product ratios from the silent reaction in the presence of 13 % (v/v) of pyridine. Here there is 60 % of... 

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