Electrochemical methods differential pulse voltammetry

Electrochemical indicator methods are based on the application of redox probe that undergoes oxidation and reduction transition due to electron transfer from electrode surface to a probe. In 2005, several studies that used methylene blue (MB) as an electrochemical indicator were published. MB is positively charged low-molecular-weight compound that can be reduced by two electrons to a leucomethylene blue (LB). The reduction process can be effectively monitored, e.g., by differential pulse voltammetry or coulometry. In presence of redox probe Fe(CN)6, the LB is oxidized to MB and the system is regenerated [44,45]. In papers by Hianik et al. [31,46], MB was used as the indicator of detection of interaction of human thrombin with DNA aptamer. The method of detection is schematically shown in Fig. 33.3B. MB binds both to DNA and to the protein. For charge transfer from electrode to MB, i.e., for MB reduction, it is important that MB should be close to the electrode surface. Therefore, the charge transfer from the electrode... 

Radi [41] used an anodic voltammetric assay method for the analysis of omeprazole and lansoprazole on a carbon paste electrode. The electrochemical oxidations of the drugs have been studied at a carbon paste electrode by cyclic and differential-pulse voltammetry in Britton-Robin-son buffer solutions (0.04 M, pH 6-10). The drug produced a single oxidation step. By differential-pulse voltammetry, a linear response was obtained in Britton-Robinson buffer pH 6 in a concentration range from 2 x 10-7to 5 x 10 5 M for lansoprazole or omeprazole. The detection limits were 1 x 10 8 and 2.5 x 10 8 M for lansoprazole and omeprazole, respectively. The method was applied for the analysis of omeprazole in capsules. The results were comparable to those obtained by spectrophotometry. 

Methods for quantitative analysis of Co indude flame and graphite-furnace atomic absorption spectrometry (AAS e.g., Welz and Sperling 1999), inductively coupled plasma emission spectrometry (ICP-AES e.g., Schramel 1994), neutron activation analysis (NAA e.g., Versieck etal. 1978), ion chromatography (e.g., Haerdi 1989), and electrochemical methods such as adsorption differential pulse voltammetry (ADPV e.g., Ostapczuk etal. 1983, Wang 1994). Older photometric methods are described in the literature (e.g.. Burger 1973). For a comparative study of the most commonly employed methods in the analysis of biological materials, see Miller-Ihli and Wolf (1986) and Angerer and Schaller... 

Recently, we presented a fast and reliable electrochemical method to quantify DNA oligonucleotides and detect single base-pair mismatches within DNA duplexes (Panke et al., 2007). Using differential pulse voltammetry (DPV),... 

Yeh and Kuwana " were the first to report on the electrochemistry of cytochrome c at doped metal oxide semiconductor electrodes. A nearly reversible electrode reaction was indicated by the cyclic voltammetry and differential pulse voltammetry of cytochrome c at tin-doped indium oxide electrodes. Except for the calculated diffusion coefficient, all of the characteristics of the electrochemistry of cytochrome c at this electrode indicated that the electrode reaction was well-behaved. A value of 0.5 x 10" cmVs was determined for the diffusion coefficient which, like previously determined values at mercury, is lower than the value obtained by nonelectrochemical methods (i.e., 1.1 X 10 cm /s " " ). The electrochemical response of cytochrome c at tin oxide semiconductor electrodes was reported to be quasi-reversible, although no details were given. " ... 

Besides these potentiometric-based methods, a series of electrochemical techniques can be applied to the detection of biomolecular interactions. Depending on the desired dynamic detection range and the specific properties of the system under study, techniques such as electrochemical impedance spectroscopy, voltage step capacitance measurements, amperometry, differential pulse voltammetry, square wave voltammetry, AC voltammetry, and chronopotentiomet-ric stripping analysis can be used for label-free detection of DNA, proteins, and peptides [1]. Often these techniques require the use of redox mediators. Electrochemical impedance spectroscopy (EIS), in particular, is a very promising technique for DNA biosensing [2,3]. 

Cyclic and differential pulse voltammetry are the most commonly used electrochemical methods for characterizing electrode surfaces (53). Cyclic voltammetry requires relatively simple and inexpensive instrumentation and the method is rapid (for further details see Chapter 8). Readouts, as shown for the example in Figure 5.4, are usually obtained. 

Electroanalytical methods have been extensively applied in sensing and biosensing. Potentiometry, amperometry, cyclic voltammetry, linear voltammetry, differential pulse voltammetry, square-wave voltammetry, and electrochemical impedance spectroscopy (EIS) represent the most-used electrochemical techniques used for biosensor fabrication and detection. 

Another electrochemical technique that is utilized in association with the DPPH method is differential pulse voltammetry (DPV), which presents a substantial increase in sensitivity in comparison with cyclic voltammetry once the residual current (capacitive current) is subtracted from the net current (Litescu and Radu, 2000 Alvarez-Diduk... 

Isomers of tocopherols in edible oils were quantified using electrochemical methods polarography (Smith et al., 1941), and differential pulse voltammetry (Galeano et al., 2004 Robledo et al., 2013). A couple of spectrophotometric assays were used to quantify tocopherols copper(II)-neocuproin system (Tiitem et al., 1997). GC-MS analysis reveals the instability at heating of y-tocopherol Ifom com oil. This isoform is converted to a-tocopherol and later degraded when temperature is increased (Sim et al., 2014). 

In general, the method of differential pulse voltammetry has been established as an advantageous method for a sensitive determination of heavy metals. On the other hand, this electrochemical method has been also intensively used to study an electrochemical behavior of MT [44-46],... 

In addition to chromatography based on adsorption, ion pair chromatography (IP-HPLC) and capillary electrophoresis (CE) or capillary zone electrophoresis (CZE) are new methods that became popular and are sufficiently accurate for these types of investigations. Other methods involving electrochemical responses include differential pulse polarography, adsorptive and derived voltammetry, and more recently, electrochemical sensors. 

The use of polarographic assays for the determination of drugs in blood is the most demanding on the detection limitations of the technique. Differential pulse polarography, stripping voltammetry, and LCEC are the only electrochemical methods currently available for routine determination of drugs below 1.0 ng/mL of blood. 

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