Liquid Chromatography Detectors - The Electrochemical Detector > Electrode Configurations > Page 91

Electrode Configurations

The electrodes can take a number of different geometric forms which have been described in some detail by Poppe (52). Some examples of different electrode configurations are shown in figure 57. Examples (A) and (B) are two common forms of thin-layer cells. (A) has the working electrode sealed into the cell wall with the reference and auxiliary electrodes situated down-stream to the working electrode.

Figure 57. Different Electrode Configurations

 

(B) is similar to (A) but with the auxiliary electrode sealed in the wall of the tube opposite the working electrode and, again, the reference electrode down-stream. (C) is a wall-jet electrode where the eluent is allowed to impinge directly onto the working electrode which is situated opposite the jet. This arrangement not only increases the value of (u) (the velocity of the liquid passing over the electrode and thus the transfer coefficient (KT)) but also scrubbs the surface of the working electrode helping to reduce the need for frequent cleaning. (D) and (E) are two examples of cylindrical electrodes; in (D) the working electrode is in the form of a rod stretching across the diameter of the sensor cell and in (E) the working electrode comprises an annular ring set in the cell wall. In both cases the auxiliary and the reference electrodes are situated down-stream to the working electrode.