Voltammetry organic

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Atomic Fluorescence Spectrometry. Gas Chromatography Pyrolysis Mass Spectrometry. Liquid Chromatography Normal Phase Reversed Phase Size-Exclusion. Polarography Inorganic Applications Organic Applications. Polymers Synthetic. Thin-Layer Chromatography Overview. Voltammetry Organic Compounds. 

See also DNA Sequencing. Enzymes Enzyme-Based Electrodes. Forensic Sciences Blood Analysis. Immunoassays, Techniques Enzyme Immunoassays. Microelectrodes. Polarography Techniques Organic Applications. Purines, Pyrimidines, and Nucleotides. Sensors Chemically Modified Electrodes. Voltammetry Organic Compounds. 

In adsorptive stripping voltammetry (AdSV) metal chelates and organic molecules are accumulated by adsorption at the surface of the working electrode. If these compounds are electrochemically active, i.e., if they are reducible or oxidizable. their subsequent voltammetric determination is possible. By this principle of so-called adsorptive stripping voltammetry, organic and organomet-allic compounds are determined in the ultra-trace range. This technique is particularly important for the trace analysis of metals that are not readily deposited as the element on mercury electrodes... 

N. A. Tananaev, simultaneously with F. Feigl, developed the spot analysis. Known Tserevitinov method for determining labile hydrogen atoms in organic compounds (1902-1907 should be noted (the method was later improved by A.P Terent ev). In the USSR, there were powerful schools in liquid-liquid extraction and inverse voltammetry. 

Differential-pulse voltammetry is an extremely useful technique for measuring trace levels of organic and inorganic species, hi differential-pulse voltammetry, fixed-magnitude pulses—superimposed on a linear potential ramp—are applied to the working electrode at a time just before the end of the drop (Figure 3-5). The current... 

Besides trace metals, adsorptive stripping voltammetry has been shown to be highly suitable for measuring organic compounds (including cardiac or anticancer drugs, nucleic acids, vitamins, and pesticides) that exhibit surface-active properties. 

Cyclic voltammetry and other electrochemical methods offer important and sometimes unique approaches to the electroactive species. Protein organization and kinetic approaches (Correia dos Santos et al. 1999, Schlereth 1999) can also be studied by electrochemical survey. The electron transfer reaction between cytochrome P450scc is an important system for... 

It was assumed for a long time that molecules can only cross a membrane in their neutral form. This dogma, based on the pH-partition theory, has been challenged [42, 43]. Using cyclic voltammetry it was demonstrated that compounds in their ionized form pass into organic phases and might well cross membranes in this ionized form [44]. 

The concentration of the transferred ion in organic solution inside the pore can become much higher than its concentration in the bulk aqueous phase [15]. (This is likely to happen if r <5c d.) In this case, the transferred ion may react with an oppositely charged ion from the supporting electrolyte to form a precipitate that can plug the microhole. This may be one of the reasons why steady-state measurements at the microhole-supported ITIES are typically not very accurate and reproducible [16]. Another problem with microhole voltammetry is that the exact location of the interface within the hole is unknown. The uncertainty of and 4, values affects the reliability of the evaluation of the formal transfer potential from Eq. (5). The latter value is essential for the quantitative analysis of IT kinetics [17]. Because of the above problems no quantitative kinetic measurements employing microhole ITIES have been reported to date and the theory for kinetically controlled CT reactions has yet to be developed. 

The electrical oscillations at the aqueous-organic interface or at membranes in the absence of any substances relative to the channel or gate were introduced. These oscillations might give some fundamental information on the electrical excitability in living organisms. Since the ion transfer at the aqueous-organic or aqueous-membrane interface and the interfacial adsorption are deeply concerned in the oscillation, it has been stressed that the voltammetry for the ion transfer at an interface of two immiscible electrolyte solutions is... 

The facilitated transfers of Na+ and K+ into the NB phase were observed by the current-scan polarography at an electrolyte-dropping electrode [12]. In the case of ion transfers into the DCE phase, cyclic voltammetry was measured at an aqueous gel electrode [9]. Both measurements were carried out under two distinctive experimental conditions. One is a N15C5 diffusion-control system where the concentration of N15C5 in the organic phase is much smaller than that of a metal ion in the aqueous phase. The other is a metal ion diffusion-control system where, conversely, the concentration of metal ion is much smaller than that of N15C5. Typical polarograms measured in the both experimental systems are shown in Fig. 2. 

Y. Kubota, Ion-Transfer Voltammetry of Organic Compounds at Organic Solvent/Water Interface. Study on Partition of Organic Compounds between Organic Solvent and Water, MS thesis, Fukui Prefectural University, Fukui 1998. 

Principles and Characteristics Contrary to poten-tiometric methods that operate under null conditions, other electrochemical methods impose an external energy source on the sample to induce chemical reactions that would not otherwise occur spontaneously. It is thus possible to analyse ions and organic compounds that can either be reduced or oxidised electrochemi-cally. Polarography, which is a division of voltammetry, involves partial electrolysis of the analyte at the working electrode. 

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