Double Differential Pulse Research Articles

Study of multistep electrode processes in triple potential step techniques at spherical electrodes

In this paper, a reversible multistep electrode process is studied by the most popular triple pulse techniques as Reverse Differential Pulse Voltammetry and Double Differential Pulse Voltammetry. The equations presented here are valid for spherical electrodes of any size (including planar and ultramicrospherical electrodes as limit cases) and can be used to describe the electrochemical behaviour of molecules with multiple redox centers, whether they are interacting or not. The comparison between results in triple and double pulse techniques for reversible multistep processes allows us to draw important conclusions regarding the suitability of such techniques and the characterization of reversible processes.

Study of a Catalytic Mechanism in Additive Differential Pulse Techniques

AbstractThe new electrochemical double pulse technique, known as additive differential normal pulse voltammetry (ADNPV) when there is no restriction on the duration of both pulses, and additive differential pulse voltammetry (ADPV) when t2≪t1, has been applied to a pseudo‐first‐order catalytic mechanism. The expressions obtained here are applicable to planar and spherical electrodes, of any radius. This is of great interest since the size of the electrode plays an important role in the preponderating of diffusive and kinetics processes. The signal obtained with this technique presents the same morphological characteristics as the triple pulse technique, double differential pulse voltammetry (DDPV) and is more advantageous than DDPV and than the double pulse one, differential pulse voltammetry (DPV).

Additive differential pulse voltammetry, instead of double differential pulse voltammetry

A new electrochemical double pulse potential technique called additive differential pulse voltammetry (ADPV) is proposed. This technique is inspired by the original idea of Birke et al. [Anal. Chem. 53 (1981) 852] of recording two differential pulse (DP) voltammograms and it consists of plotting the sum of these two signals versus the first pulse potential, although in this paper the proposal is to obtain the ADPV signal through just one experiment. ADPV behaves in an identical way to the triple-pulse technique double differential pulse voltammetry (DDPV) for reversible processes when diffusion coefficients are equal for spherical electrodes and for any value of diffusion coefficients in planar electrodes. In the case of reversible electrode processes with amalgamation of reaction product or other more complex processes, ADPV is more advantageous than DDPV. This is due, among other reasons, to the fact that, under these conditions, a double potential step is much simpler to analyse than a triple potential step.

Oxygen-sensing microdialysis probe for in vivo use.

Electrochemical conditions were optimized to allow the metal tube used for the shaft of commercial microdialysis (MD) probes to be coated with gold. In in vitro tests with phosphate-buffered Ringer's solution using double differential pulse amperometry (DDPA), the gold-coated shafts were capable of specifically measuring the reduction of oxygen and the oxidation of ascorbic acid in the presence of high concentrations of potentially interfering endogenous substances. By using fixed-potential amperometry (FPA), the gold-plated shaft also measured oxygen with minimal interference from high concentrations of potentially interfering endogenous substances. Concentric design MD probes were constructed that used a metal shaft (O.D = 0.4 mm), fused silica inlet and outlet tubes, and a 1.5 mm dialyzing membrane (O.D = 0.2 mm). A 0.5-0.7 mm gold collar was electroplated onto the metal shaft approximately 0.5 mm above the dialyzing membrane. The nongold outer surface of the MD probe was coated with an insulating polymer. In vivo tests demonstrated that DDPA was not suitable for use with this gold microdialyzing electrode (GMDE). However, brain oxygen levels were satisfactorily measured using FPA. In urethane-anesthetized rats, the reduction current to oxygen in the striatum was increased by brief (1 min) inhalation of O2 or CO2 and decreased by inhalation of N2. Transient application of noxious stimuli (foot pinch) increased cerebral O2, whereas bilateral carotid artery occlusion and death decreased striatal O2. The responses of the GMDE were indistinguishable from the reduction current simultaneously measured from a conventional carbon fiber electrode implanted adjacent to the gold-plated area of the MD shaft. Basal levels of striatal O(2) were 20 +/- 5 microM (n = 4) for the GMDE and 30 +/- 11 microM (n = 3) for the carbon fiber. The GMDE was robust and could be used for at least three animals. This technique can be used to provide information about the oxygen status of the tissue adjacent to the dialyzing membrane without the need for implantation of an additional electrode.

General analytical solution for a reversible i- t response to a triple potential step at an SMDE in the absence/presence of amalgamation

The theory corresponding to triple potential step chronoamperometry for a reversible charge transfer reaction in a static mercury drop electrode is presented. The equation for the current has been deduced assuming different diffusion coefficients for oxidized and reduced species and is valid when the reaction product is soluble in both the electrolytic solution and the electrode. The validity of equations proposed was verified by comparing theoretical i- t, double differential pulse and reverse differential pulse curves with those obtained experimentally for the system Cd 2+ Cd(Hg) . It can be concluded that the double differential pulse and reverse differential pulse techniques are more sensitive to the presence or absence of amalgamation than double pulse techniques.

Double differential pulse voltammetry

From the solution obtained in previous work for the faradaic response to a triple pulse of potentials, the double differential pulse technique can be defined through the equation I ddp = i 3 − 2 i 2 + i 1, where i j ( j = 1, 2, 3) is the current corresponding to the potential E j . The solution to this equation, which is valid both for a static mercury drop electrode and for a dropping mercury electrode, was studied, and experimental conditions for the analysis of the corresponding curves are proposed. Likewise, approximate solutions and analysis criteria for completely reversible and irreversible processes are reported. The solutions were checked against experimental examples of well-known processes. The analytical and kinetic advantages of this technique are discussed.