Pulse polarogram

The limiting current was 5.67 tA. Verify that the reduction reaction is reversible, and determine values for n and 1/2. The half-wave potentials for the normal pulse polarograms of Pb + in the presence of several different concentrations of OH are shown in the following table. 

FIGURE 3-6 Differential pulse (a) and DC (b) polarograms for a 1.3 x 10 5 M chloramphenicol solution. (Reproduced with permission from reference 7.)... 

FIGURE 3-7 Normal-pulse (curve A) and differential-pulse (curve B) polarograms for a mixture of 1 mg L-1 cadmium and lead ions. The electrolyte is 0.1 M HNOj. 

A precursor of the studies on electron transfer reactions between short-lived radicals and colloidal particles was the development of a fast pulse radiolysis method to measure. the polarograms of radicals in the 10 s range . After considerable information had been acquired about the electron transfer reactions of a few dozen radicals at the mercury electrode, this compact electrode was replaced by metal colloids somewhat later, by semiconductor colloids These studies led to the detection of the electron-storing properties of certain colloids and of reactions of the stored electrons. 

Sometimes besides direct pulses, reverse pulses are also applied (Tacussel PRG 5 polarograph), because by tracing out the polarogram using first positive-, then negative-going pulses, one may study the reversibility of reactions. 

Figure 2.1. Differential pulse polarographic verification of sunlight-induced bromate production in chlorinated seawater. Curve (a) polarogram from untreated seawater, seawater immediately after chlorination to 4.9 ppm, or chlorinated seawater kept in the dark for 4 h at 40 °C. Curve (b) polarogram from chlorinated seawater exposed to full sunlight for 70 min. Curve (c) standard 1.0 x 10-6 M sodium bromate in seawater, offset with respect to curves (a) and (b). Polarograms were recorded at 25 °CandpH 8.35 SCE saturated calomel electrode. From [19]...

Differential pulse polarograms for the oxidation of R4Pb (R = Ph, Me, Et, Bu) in CH2C12 on DME all show an electrode response for oxidation. This DPP response is, however, spread over a wide potential range of 300 mV indicating that several processes are reflected by this wave. The DPP responses for several lead compounds are cited in Table 6. 

Figure 6.23 Normal pulse polarogram of the reduction of Pb (10 mol dm ) at a DME. The ionic electrolyte was KNO3 (0.1 mol dm ). Reproduced from Greef, R., Peat, R., Peter, L. M., Pletcher, D. and Robinson, J., Instrumental Methods in Electrochemistry, Ellis Horwood, Chichester, 1990, with permission of Professor D. Pletcher Department of Chemistry, University of Southampton, Southampton, UK.

Phosphorescence, 191, 223 Photoacoustic detector, 177 Photoelectric effect, 238 Photoelectron, 238 Photovoltaic, 176 Plasam, 274 Plate, 10 Polarogram, 361 Polarographic wave, 361 Polyethylene glycols, 32 Polysiloxanes, 31 POPOP, 333 PPO, 333 Precession, 129 Precision, 386 Pulse polarography, 364 Pulsed NMR, 155 Pyroelectric, 175... 

Figure 17-19 Comparison of polarograms of 5 mM Cd2 in 1 M HCI. Waveforms are shown in Figures 17-15 and 17-18. Sampled current drop time = 1 s, step height = 4 mV, sampling time = 17 ms. Square wave drop time = 1 s, step height = 4 mV, pulse period = 67 ms, pulse height = 25 mV. sampling time = 17 ms.

The mathematical description of the normal pulse polarogram is easily derived from either eqn. (33) or eqn. (38). For sufficiently large lt 2 values, eqn. (35b) holds and reversible behaviour is observed corresponding to... 

The resulting expressions for —jF/F = tijVi + nnvn may be used either to analyze the current vs. time functions at fixed potential [128] or the current vs. potential function, e.g. measured in the normal pulse polaro-gram or the d.c. polarogram [127]. In the latter reference, the mathematics pertaining to the dropping mercury electrode (expanding plane... 

We therefore advise that the reader should consult a recent series of papers published by Galvez et al. [171, 172] encompassing all the mechanisms mentioned in Sect. 7.1, elaborated for both d.c. and pulse polarography. The principles of the Galvez method are clearly outlined in the first part of the series [171]. It is similar to the dimensionless parameter method of Koutecky [161], which enables the series solutions for the auxiliary concentration functions cP and cQ exp (kt) and

combined directly with the partial differential equations of the type of eqn. (203). In some of the treatments, the sphericity of the DME is also accounted for. The results are usually visualized by means of predicted polarograms, some examples of which are reproduced in Fig. 38. Naturally, the numerical description of the surface concentrations at fixed potential are also immediately available, in terms of the postulated power series, and the recurrent relationships obtained for the coefficients of these series. 

The behavior of the normalized normal pulse polarograms at different pulse time values is shown in Fig. 3.8, which clearly shows the influence of the pulse time on... 

Figure 4. Cyclic voltammogram and differential pulse polarogram of electrodes prepared as in Fig. 2, spectrum E. Recorded using solution conditions from Fig. 3. The differential pulse polarogram was recorded with a scan rate of 2 mV/s.

Figure 3.6 Potential-time sequence for (a) normal-pulse polarogram and (b) differential-pulse polarogram. The current-time response for the latter is given by (c), with fi and f3 the times at which current is measured, t2 the time at which pulse is applied, and r4 the time at which pulse is removed.

Figure 3.7 Pulse polarograms for 10"4 M Cd11 ion (a) normal and (b) differential modes.

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