Differential pulse voltammetry peak potential

TABLE 8.5 Square Wave Voltammetry or Differential Pulse Voltammetry Peak Potentials (in V Versus Fc + /Fc) of Multimetallofullerenes and Metal Carbide Fullerenes... 

Selectivity Selectivity in voltammetry is determined by the difference between half-wave potentials or peak potentials, with minimum differences of+0.2-0.3 V required for a linear potential scan, and +0.04-0.05 V for differential pulse voltammetry. Selectivity can be improved by adjusting solution conditions. As we have seen, the presence of a complexing ligand can substantially shift the potential at which an analyte is oxidized or reduced. Other solution parameters, such as pH, also can be used to improve selectivity. 

Electrochemical communication between electrode-bound enzyme and an electrode was confirmed by such electrochemical characterizations as differential pulse voltammetxy. As shown in Fig. 11, reversible electron transfer of molecularly interfaced FDH was confirmed by differential pulse voltammetry. The electrochemical characteristics of the polypyrrole interfaced FDH electrode were compared with those of the FDH electrode. The important difference between the electrochemical activities of these two electrodes is as follows by the employment of a conductive PP interface, the redox potential of FDH shifted slightly as compared to the redox potential of PQQ, which prosthetic group of FDH and the electrode shuttling between the prosthetic group of FDH and the electrode through the PP interface. In addition, the anodic and cathodic peak shapes and peak currents of PP/FDH/Pt electrode were identical, which suggests reversibility of the electron transport process. 

For compound (Scheme 1 and Table 1) the oxidation pattern is quite different the differential pulse voltammetry exhibits two peaks of equal height, both corresponding to a two-electron oxidation process (Figure 11). The first oxidation occurs at nearly the same potential as the four-electron process of compound 6F. This shows that, as expected, the two Os(bpy)2( i-2,3-dpp) units are the first to be oxidised (Table 2). The second process concerns the oxidation of the two Ru(bpy)2(p-2,5-dpp) units. Since such units lie far away from the previously oxidized Os-containing units, their oxidation occurs at a potential (Table 2) close to that of the equivalent peripheral units of 6D. As in the case of the compounds 6A-F the oxidation of the two inner units are displaced outside the accessible potential window. 

For lOA the differential pulse voltammetry exhibits only one six-electron peak which corresponds to the simultaneous one-electron oxidation of the six peripheral, noninteracting Ru units (Table 2 and Figure 13). Oxidation of the central and intermediate metal ions cannot be observed in the accessible potential window. 

The increase of the potential, at which the oxidation of the metal ions coordinated to the 2,3-Medpp ligand takes place, is further evidenced by the different behavior of the tetranuclear compound 4A and (Scheme 1 and Thble 1). As clearly indicated by the differential pulse voltammetry, which exhibits a three-electron oxidation peak for the former and a one-electron oxidation peak for the latter (Figure 14), in 4A the oxidation involves the three peripheral Ru units (as mentioned before), whereas in 4J, only the central Ru unit can be oxidized in the accessible potential window (Table 2). 

Electrochemical oxidation of natural and synthetic DNA performed at pyrolytic graphite [16] and glassy carbon [3-6,17,18] electrodes showed that at pH 4.5 only the oxidation of the purine residues in polynucleotide chains is observed. Using differential pulse voltammetry, the less positive peak corresponds to the oxidation of guanine residues and the peak at more positive potentials is due to the oxidation of adenine residues. 

Pang et al. [54] studied the electrochemical behavior of L-dopa at SWCNT-modified GCE. Before starting, the electrode was immersed for 120 s in the L-dopa solution. L-dopa showed an irreversible behavior at bare GCE with peak potential separation of 161 mV. On the contrary, a quasi reversible behavior with peak potential separation of 55 mV was obtained at the SWCNTs-modified electrode. Experiments performed by differential pulse voltammetry showed a... 

Differential Pulse Voltammetry (DPV). There are two main differences between differential pulse and NPV. The waveform for DPV, Figure 10(b), involves a pulse of amplitude AEpuise like that of the normal pulse sequence but the step back down is not to the initial potential, instead it is to a specific differential that is used during the measurement. Also, there are two sampling periods for each pulse, once at the end of the potential step up, like in NPV, and an additional sampling period at the end of the step down in potential, after which the difference in the two signals is recorded hence the name DPV. This pulse sequence results in a current signal response different from that of NPV, shown in Figure 10(b). If the electrochemical process is reversible, the peak half width, A p/2, is determined by equation (9), ... 

Table 14.3 A comprehensive list of the NO peak potentials (mV)/oxidation currents (pA) determined for all individual member of the metalloporphyrin library (left general chemical structure) as assessed by means of automated differential pulse voltammetry (right Ryabova et al.75...

Mix fsDNA solution and H33258 at a final concentration of 1 pM in 50mM PBS and pipet an aliquot (20 pL) of this mixture on the gold or carbon SPE surface. Measure immediately using linear sweep voltammetry (LSV) after an equilibration time of 10s, with a sample interval of lmV, and a scan rate of 0.1 V/s from 0 to IV (Fig. 5). Alternatively, cyclic voltammetry (CV) can be applied with a scan range between 0 and 1V at a sweep rate of 0.1 V/s. For differential pulse voltammetry (DPV) measurements, the potential is scanned from 0 to 0.90V with a step potential of 4mV, pulse amplitude of 50mV, and a pulse period of 0.20s at a scan rate of lOmV/s. The current height is recorded at the peak potential (-0.6V) for analytical evaluation of the measurements. All measurements should be carried out at room temperature. 

Differential pulsed voltammetry (DPV) is a technique in which potential pulses of fixed but small amplitudes are superimposed periodically on a linear voltage ramp. The most commonly used working electrode is the SMDE and one pulse is applied for each drop. The mV pulse is applied near the end of the life of the mercury drop. Current is measured once before the pulse and after the pulse. The difference between the currents is plotted against potential (Figure 5.8). The resultant peak-shaped current-voltage signal, which... 

The carbon-fiber tip modification process consists of poly-(TMHPP)Ni film deposition on the electrode surface and confirmation of deposition followed by demetalation to poly-TMHPP and confirmation of demetalation. Polymeric film is deposited from a 0.25 mM (TMHPP)Ni solution in 0.1 M sodium hydroxide by constant-potential electrolysis at 0.70 V. The number of monolayers deposited is dependent on the initial concentration of (TMHPP)Ni and the time of electrolysis. At the end of the deposition time, the electrode is immersed in 0.1 M sodium hydroxide. The presence of (poly-TMHPP)Ni film on the electrode surface is confirmed by a peak at Ep = 0.55 V, attributable to the Ni(II)/Ni(III) couple, in a differential pulse voltammetry scan. The (poly-TMHPP)Ni film is demetalated in a chemical process by placing the electrode in 0.1 M HCl. 

Single-fiber sensors and catheter-protected sensors can operate in an amperometric or voltammetric mode. In both methods a current proportional to NO concentration is measured. Of the several voltammetric methods available, differential pulse voltammetry (DPV) is most suitable for the measurement of NO. In DPV, a potential modulated with rectangular pulses is linearly scanned from 0.4 to 0.8 V. The resulting voltammogram (alternating current versus voltage plot) contains a peak due to NO oxidation. The peak current should be observed at a potential of 0.63-0.67 V which depends on the pulse amplitude. This potential is the characteristic potential for NO oxidation on Nafion coated porphyrinic sensor. 

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