Differential pulse voltammetry studies

MacFarlane, D.R., Zhou, Z., Newman, P.J., 2004. Differential pulse voltammetry studies of heavy metal fluoride melts. J. Appl. Electrochem. 34 (2), 197-204. 

It has been demonstrated that the presence of CNTs greatly increases the oxidation peak current of 6-benzylaminopurine. The CNT-modified electrode is suitable for the determination of trace amounts of benzylaminopurine and has the advantages of high sensitivity, quick response, and good stability [86], Wang et al. have studied the electro-catalytic oxidation of thymine at a a-cyclodextrin incorporated CNT coated electrode in an alkaline media. A sensitive detection scheme for thymine has been further developed by using differential pulse voltammetry [87], The electrochemical determination... 

The electrochemical behavior of the components of a commercial plant growth stimulator (Sviton) was studied. This included determination of o-nitrophenol, p-nitrophenol, 2-methoxy-5-nitrophenol and 2,4-dinitrophenol by differential pulse voltammetry at a hanging mercury drop electrode. The optimum conditions were established for their quantitation over the 1 x 10 7 to 1 x 10-5 M range516. 

The adsorption behavior of the psychotropic drug flunitrazepam (256) at the hanging mercury drop electrode was studied by staircase voltammetry and by adsorptive stripping differential pulse voltammetry. 256 can be determined down to nanomolar levels by using adsorptive preconcentration prior to the differential pulse voltammetry scan. The method was applied to determination of 256 in human urine530. 

Jarbawi and Heineman have used differential pulse voltammetry and chronocoulometry to study the effect of immersing a wax-impregnated graphite electrode in an aqueous solution of chlorpromazine [157]. Extraction of substance into the electrode and absorption at the interface were both found to occur. 

Rajca and co-workers have studied star-branched and dendritic high-spin polyradicals which are potential organic magnets. Representative data were obtained for the model tetra-anionic compound 55. Three redox waves were observed by cyclic voltammetry and differential pulse voltammetry for a four-electron process between the potentials of -2.00 and -1.20 V (vs. SCE). Electrochemical experiments with these materials have usually been performed at 200 K. The polyradicals, which are less stable for systems with more unpaired electrons, have been characterized by spectroscopic studies, ESR data, and SQUID magnetometiy. 

Investigation of thiol- and disulfide-modified oligonucleotides with either 25 or 10 bases, or base pairs immobilized on polycrystaUine and Au(lll) electrodes has also been carried out [171]. In these studies, several techniques were employed, including X-ray photoelectron spectroscopy, cyclic and differential pulse voltammetry, interfacial capacitance data, and in situ STM. 

Recent studies describe the use of cyclic voltammetry in conjunction with controlled-potential coulometry to study the oxidative reaction mechanisms of benzofuran derivatives [115] and bamipine hydrochloride [116]. The use of fast-scan cyclic voltammetry and linear sweep voltammetry to study the reduction kinetic and thermodynamic parameters of cefazolin and cefmetazole has also been described [117]. Determinations of vitamins have been studied with voltammetric techniques, such as differential pulse voltammetry for vitamin D3 with a rotating glassy carbon electrode [118,119], and cyclic voltammetry and square-wave adsorptive stripping voltammetry for vitamin K3 (menadione) [120]. 

Far from the metal trace analysis, our initial studies with BCFMEs were focused on the determination of folic acid [122], In this case, the main goal was the optimisation of the electrode pretreatment for this analyte. An acidic medium (0.1M perchloric acid) was considered optimum for folic acid determination by differential pulse voltammetry. A linear range between 2.0 x HT8 and 1.0 x 10 6M with a detection limit of 1.0 x 10 8M was obtained. Nevertheless, in this work, the adsorptive properties of the folic acid on mercury were noted and the employment of mercury-coated carbon fibre UMEs for folic acid determination has been targeted as a future goal. 

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. 

Although alternate methods of determining particle sizes have not been explored with bimetallic DENs, a study by Kim, Garcia-Martinez, and Crooks is worth noting. In this study, the investigators used differential pulse voltammetry to estimate the size of dendrimer-templated Pd and Au nanoparticles [32], This study estimated particle sizes to be very close to ideal sizes calculated from the metakdendrimer stoichiometry and the metallic radius of each metal. Further, the study concluded that TEM measurements overestimated the size of the smallest Pd nanoparticles due to inadequate point-to-point resolution [32],... 

Potentiodynamictechniques— are all those techniques in which a time-dependent -> potential is applied to an - electrode and the current response is measured. They form the largest and most important group of techniques used for fundamental electrochemical studies (see -> electrochemistry), -> corrosion studies, and in -> electroanalysis, -+ battery research, etc. See also the following special potentiodynamic techniques - AC voltammetry, - DC voltammetry, -> cyclic voltammetry, - linear scan voltammetry, -> polarography, -> pulse voltammetry, - reverse pulse voltammetry, -> differential pulse voltammetry, -> potentiodynamic electrochemical impedance spectroscopy, Jaradaic rectification voltammetry, - square-wave voltammetry. 

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... 

Downard el al. [9] have reported the application of a phenylacetate layer to glassy carbon macroelectrodes. Their study determined dopamine levels in the presence of ascorbic acid. Differential pulse voltammetry of dopamine and ascorbic acid at both modified and unmodified electrodes showed almost a six-fold enhancement of dopamine anodic peaks at the modified electrodes. For ascorbic acid, while the magnitude of its anodic current remained similar at modified electrodes, the peaks were no longer as well-resolved as for unmodified electrodes. 

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... 

---