Tast-Polarography

If we realize that the drop life (pulse time, it shows that NPP yields a signal about six times higher than that of DC Tast polarography. 

The electrode reaction of triamterene 15 was elucidated by means of DCP, Tast polarography, cyclic voltammetry, microcoulometry, controlled potential electrolysis, and spectroscopy (ultraviolet/visible (UVA is), NMR). Two steps of reduction independent of pH were observed two-electron reduction of 15 resulted in the formation of 17. The first reduction wave of 15 was assumed to be due to irreversible two-electron reduction forming unstable 16, which tautomerized to 17, and the second reduction wave was ascribed to two-electron reduction of 17 to the tetrahydro product, 18 (Scheme 2). 

Fig. 10.8. Tast polarography showing (a) Variation of total current (/c + /f) and sampling just before drop fall at time t = r (b) The resulting polarogram.

Tast polarography (sampled curent polarography) -> DC polarography with -> current sampling at the end of each drop life. This way the ratio of faradaic current to -> charging current is enhanced and the - limit of detection can be decreased. 

We will consider five subtopics tast polarography and staircase voltammetry, normal pulse voltammetry, reverse pulse voltammetry, differential pulse voltammetry, and square wave voltammetry. Tast polarography, normal pulse voltammetry, and differential pulse voltammetry form a sequence of development rooted historically in polarography at the DME. To illustrate the motivating concepts, we will introduce each of these methods within the polarographic context, but in a general way, applicable to both the DME and SMDE. Then we will turn to the broader uses of pulse methods at other electrodes. Reverse pulse voltammetry and square wave voltammetry were later innovations and will be discussed principally outside the polarographic context. 

Figure 7.3.2 Staircase waveform and sampling scheme for tast polarography and staircase voltammetry. The experiment is a series of cycles in which a potential is established and held constant for a period, a current sample is taken at time r after the start of the period, then the potential is changed by an amount AF. In tast polarography, the mercury drop is dislodged at the end of each cycle, as indicated by the vertical arrows. In staircase voltammetry, this step is omitted. The time between the current sample, drop dislodgment, and the change in potential is exaggerated here. Usually it is negligible and the cycle period is essentially the same as r.

Figure 7.3.4 Schematic experimental arrangement for tast polarography. Staircase voltammetry is carried out at a stationary electrode with the same system except the drop knocker.

The current sampling technique, tast polarography, formerly advised for the elimination of serrations only, grew to become the standard method for recording the polarographic waves. The current is detected in the interval of several milliseconds at the end of the drop-life (see Fig. 

Fig. 15. Principle of the current sampling in tast polarography illustrated on instantaneous currents I. I — t plots during the drop time are followed but sampled in the period tj only 1, faradaic current 2, charging current 3, resulting current.

A Tast-polarographic system was used (Radiometer P04 Polariter and a E65 mercury drop electrode) with a 1 s drop time with a 0.5 s drop life. The collection and preparation of the RBC for a Tast-polarography as well as the experimental details and findings have been reported (38). A summary of this work is presented here. 

In DC polarography the lower sensitivity limit is in the region from 10 to 10 mol.l perhaps still lower with higher electron consumptions (e.g. with nitro compounds). An increase in sensitivity was reached only by charging current compensation[5] or, later, by the so-called tast polarography[6]. 

Tast polarography (sampled curent polarography) DC polarography with current sampling at the... 

Elbei AW (1960) Tast polarography (in German). Fresenius Z Anal Chem 173 70-73... 

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