Static mercury drop electrode SMDE

Fig. 3.28. Static mercury drop electrode (SMDE) (Courtesy of PARC). 

The Model 303A static mercury drop electrode (SMDE) has received continuous design improvements (cf., Fig. 3.28 and associated explanation), e.g., the larger drop size afforded by the 303A design has yielded a further increase in sensitivity and the flip of a switch converts it into an extremely stable HMDE for stripping and/or square-wave voltammetry. ... 

Temperature effect on the electrodeposition of zinc on the static mercury drop electrode (SMDE) and glassy carbon (GG) electrode was studied in acetate solutions [44]. From the obtained kinetic parameters, the activation energies of Zn(II)/Zn(Hg) process were determined. 

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]. 

The following types of mercury electrodes have been widely used for voltammetry dropping mercury electrode (DME), hanging mercury drop electrode (HMDE), static mercury drop electrode (SMDE), streaming mercury electrode (SME), and mercury film electrode (MFE). We begin our discussion with a description of the construction and properties of the DME because this electrode has a long history and continues to be used for both analytical and fundamental studies. 

The static mercury drop electrode (SMDE) was first introduced commercially in the late 1970s by EG G Princeton Applied Research [27]. It utilizes a method of drop formation in which the mercury drop is dispensed rapidly and then allowed to hang stationary at the capillary tip. When used in a DME mode of operation, the drops can be repetitively formed and dislodged at desired time... 

When the electrode does not have macrometric dimensions (i.e., for a radius smaller than 0.05 cm for a time of experiment of 1 s), the geometry becomes fundamental. In this section, special detail will be paid to spherical geometry. The use of spherical electrodes such that the Static Mercury Drop Electrode (SMDE) offers important advantages over solid electrodes on account of its smooth and... 

Linear and cyclic voltammetric experiments were carried out by using a Metrohm E-612 scanner coupled to a Metrohm E-611 detector. Current-potential curves were recorded by a Graphtec WX-4421 X-Y recorder. A Metrohm 663 static mercury drop electrode (SMDE) with a drop area of 0.47 mm was used as working electrode for the stripping experiments. Potentials are referred to an Ag/AgCl/KCl 3 M electrode. 

The most practical electrodes for ASV are the hanging mercury drop electrode (HMDE) (formed at the tip of a glass capillary), especially in its static mercury drop electrode (SMDE) version, and the thin mercury film (TMF) electrode (Figure 3). 

Quite simple is the work with the static mercury drop electrode (SMDE) requiring few instrumental adaptation only. The electrode mechanics (a relay-operated valve) allows to form the final drop-size within several tens up to several hundreds of milliseconds [51]. The current is not sampled before the drop is stopped. This procedure totally eliminates the charging current and lowers the detection limit to the 10" M level. 

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) ... 

Static Mercury Drop Electrode. Recent developments have led to the static mercury drop electrode (SMDE). which today is the preferred electrode for polarographic analysis. Compared with the DME, the drops from this type of electrode can be renewed more frequently, about once or twice per second. A microvalve with opening times of 20 - 200 ms controls the mercury inflow to the capillary. During each open period a mercury drop forms, whose surface area remains constant after the valve closes. 

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