Polarogram normal-pulse

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 3-7 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. 

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.

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... 

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 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.

Polarogram — Figure. Potential program and the respective (a) direct current (DC) (staircase ramp), (b) normal pulse (NP) and (c), differential pulse (DP) polarograms of 0.1 mM Cd(NC>3)2. All measurements were in water with 0.1 M KC1, E is versus a SCE, scan rate = 2 mVs-1 and drop time = 2 s. Differential pulse height = 10 mV... 

Figure 2. Wavetrain for a normal-pulse polarogram, showing a series of pulses of increasing heights. [Reproduced with permission from A. Bond, Modem Polarographic Methods in Analytical Chemistry, Marcel Dekker, New York, 1980.]...

Figure 7.3.11 is a block diagram of the experimental system and Figure 7.3.12a is an actual polarogram for 10 M Cd " in 0.01 M HCl. For comparison, the normal pulse response from the same system is given in Figure 7.3.12/ . 

Differential pulse polarography also produces an ambiguous record for this kind of situation, as shown in Figure 7.3.18c. A peak is seen only for the Cd " reduction, because the trace covers potentials only on the negative side of the Fe wave. We note again that the differential pulse polarogram approximates the derivative of the normal pulse record hence distinct peaks will not be seen in DPV (or in SWV) unless distinct waves appear in NPV. 

A. Account for these results. Standard addition of 10 M Cu " elevates the peaks in both cases by 0.24 Comment on the feasibility of obtaining polarograms of any type on this solution. What responses would you expect for dc, normal pulse, and differential pulse experiments Would any of these supply useful analytical information ... 

Figure 13 Normal pulse polarogram for a DME displaying a typical sigmoidal current response plotted versus potential (V vs. SCE) ...

Fig. 3.3b. Comparison of (i) the normal pulse and (ii) classical dc polarograms from the same solution at the same recorder and...

According to Katano and Senda [15,16], the transfer of Pb ions in the presence of citrate in W facilitated by 1,4,7,10,13,16-hexathiacyclo-octadecane is limited by the dissociation reaction of Pb + ions from their complexes with citrate in W, while the transfer of Pb ions across the interface and the complex formation of Pb ions with the ionophore in O are fast. The quantitative analyses of linear-sweep voltammograms and normal-pulse polarograms consistently show that the entire process is described by a CE mechanism and that the dissociation and association rate constants of the Pb -citrate complex are... 

Figure 15.29 Normal pulse polarogram of ions (5 ppm) in 1 M KNO3 (scan rate 5 mV/s, 2 s drop time).

Measure the mercury flow rate with the column height set as for problem 15.2. Collect about 20 droplets under the electrolyte (why ) and determine the drop lifetime with a stopwatch. Use the Ilkovic equation to calculate the diffusion equation for Pb ion and compare your derived value with a literature value. Record a normal pulse polarogram of (a) 1.00 x 10 MZn +, (b) Cd ion and, (c) Cu ion in a degassed 1 M KNO3 electrolyte. Construct a graph of potential ( ) vs. log[(/L — i)/i. Determine the value of n from the slope and comment on the reversibility of this reaction. How does the electrolyte temperature affect the slope of this curve ... 

The relationship between current and voltage for a well-degassed solution of Pb(N03)2 is shown in Figure 15.29. (This polarogram is actually a normal pulse polarogram, not a DC polarogram. 

Fig. 4. Normal pulse polarogram of Yb (L) in 0.3 M sodium triflate acetonitrile solution. Negative potentials (V vs SCE) are plotted to the right and reduction currents are plotted upward. The inset shows a plot of —E vs log 0 l —i//) for the normal pulse polarogram.

Figure 7 shows the hnear-sweep (LS) polarograms of TP. The wave peak is sharp and symmetrical. The normal pulse polarogram at low concentrations of TP is also peak-shaped. These facts indicate that the reactant is adsorbable (Flanagan et al., 1977). Under the optimum conditions for analysis (0.4 M NH3-NH4CI and 1 x 10 M TP at pH 9), the presence of rare earth ions decreases the height of the TP peak linearly. If the amount of rare earth ions added is small, there is no new peak after the reduction peak of TP. If the concentrations of TP and the rare earth are... 

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

Fig. 24. Plot of normalized peak current [(peak current)/(concentration DNE)] from differential pulse polarograms of 5.0 ml of phosphate buffer solution containing dinitroestriol (DNE), bovine IgG, estriol, and (or) estrogen-specific antisera. O, DNE 7.0 xM plus bovine IgG as shown on bottom scale A, DNE 7.0 jlA1 plus bovine IgG (0.7 g/liter) and estriol (74 jxM) , DNE 8.8 iM plus bovine IgG (0.3 g/liter) and estrogen-specific antisera as shown on top scale , DNE 8.8 pM plus bovine IgG (0.3 g/liter), estrogen-specific estriol (0.9 g/liter), and estriol (6.0 pM). (From Wehmeyer et al., 1982, with permission.)...

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