Static mercury drop electrode Polarography

Although normal pulse polarography was developed mainly for analytical purposes, it is a valuable and simple method to study kinetics of not-too-fast electrode reactions. As the other controlled potential techniques, it has the advantage of being applicable to systems where only one of the redox components is present initially. The technique is closely related to d.c. polarography [11] and the expressions discussed in this section are directly applicable to the case of d.c. polarography performed with the static mercury drop electrode (SMDE) if the correction for the spherical shape of this electrode is negligible [21, 22]. 

In recent years non-faradaic processes which occur within adsorption layers at electrodes are gaining increasing attention. Experimentally, additional capacity currents were observed due to phase transitions between different immissible adsorption layer structures. An example is illustrated in Fig.3. The potential dependence of the non-faradaic charge density (qc) at the interface static mercury drop electrode/0.9 M NaNOa and 3-methylisoquinoline (3 MiQ) with a surfactant concentration of 0.545 times the saturation value (c ) were measured with the integrated dc polarography. The qc — steps at certain potentials are caused... 

However, there is another recently Introduced improvement in polarographic experimental techniques, namely the static mercury drop electrode (SMDE)[12,13]. This electrode represents a non-electronic approach to obtaining a constant electrode surface. It follows from recent literature on analytical applications of polarography and from the comparison of pertinent equations for the polarographic current in DC and DP polarography (under assumption of linear diffusion) ... 

Figure 5. Measuremenl lechnique of current sampled DC polarography with the static mercury drop electrode as working electrode...

Hanging mercury-drop electrode (HMDE) A commonly employed working electrode in polarography. The HMDE is often preferred to the experimentally simpler dropping mercury electrode (DME) because resultant polarograms do not have a sawtoothed appearance and because accumulation (for stripping purposes) is readily achieved at its static surface. 

As the later chapters indicate, a given question concerning a chemical system usually can be answered by any one of several electrochemical techniques. However, experience has demonstrated that there is a most convenient or reliable method for a specific kind of data. For example, polarography with a static or dropping-mercury electrode remains the most reliable electrochemical method for the quantitative determination of trace-metal ion concentrations. This is true for two reasons (1) the reproducibility of the dropping-mercury electrode is unsurpassed and (2) the reference literature for analysis by polarography surpasses that for any other electrochemical method by at least an order of magnitude. 

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