Anodic oxidation of substituted methoxyphenols. Mass spectrometric identification of methanol formed

Petek, M.; Bruckenstein, Stanley; Feinberg, Benjamin A.; Adams, Ralph N.

doi:10.1016/s0022-0728(73)80328-6

Cited by 65 publications

(23 citation statements)

References 5 publications

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“…As it is show in Figure 1A in the first anodic scan the irreversible oxidation wave, Ia, is observed at ca. 0.80 V. In subsequent cycles a reversible redox couple develops at E8' of 0.51 V. Essentially the same behavior, i.e., a single oxidation peak in the first scan followed by the development of a reversible redox couple at a lower potential, was previously observed for monomethylated catecholamine derivatives [16], surface-grafted [17] and electropolymerized [18] eugenol. The cyclic voltammogram reaches a steady shape after ca.…”

Section: Resultssupporting

confidence: 74%

Preparation and Characterization of a Lignin Modified Electrode

Milczarek

2007

Electroanalysis

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Alkali lignin undergoes strong adsorption on polycrystalline gold electrodes. Subsequent oxidation in a sulfuric acid solution leads to a restructured redox-active polymer that shows features characteristic for surface confined species. Surface coverage of up to 4.40 Â 10 À10 mol cm À2 may be obtained depending on the adsorption time or lignin concentration in the adsorption solution. Using Lavirons approach the electron-transfer rate constant and the transfer coefficient were found to be 8.9 s À1 and 0.35, respectively. The formal potential of the redox couple shifted negatively with pH at a rate of ca. 60 mV/pH unit, suggesting a 2 e/2 H þ reaction. The redox couple was also found to be a good mediator for electrochemical ascorbic acid oxidation in neutral phosphate buffer with ca. 250 mV reduction of the oxidation overpotential.

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Section: Resultssupporting

confidence: 74%

Preparation and Characterization of a Lignin Modified Electrode

Milczarek

2007

Electroanalysis

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“…The further oxidation of the radical into a phenoxonium ion is, however, greatly facilitated, being 0.5 V less positive than that of BHT. As has been previously pointed out for BHA [21] and for other 4-methoxy phenols [17], the phenoxonium ion resulting from the two-electron oxidation is chemically attacked by water to form the dienone derivative which is unstable and is further transformed into the p-quinone with a release of methanol [22,23]. This fully agrees with the voltammograms recorded in both acidic and alkaline solutions (Fig.…”

Section: Nature Of the Processessupporting

confidence: 90%

Voltammetric Behavior and Simultaneous Determination of the Antioxidants Propyl Gallate, Butylated Hydroxyanisole, and Butylated Hydroxytoluene in Acidic Acetonitrile-Water Medium Using PLS Calibration

Galeano-Dı́az¹,

Cabanillas

Franco

et al. 1998

Electroanalysis

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The voltammetric behavior of propyl gallate (PG), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) has been studied at the glassy carbon electrode (static and rotating), in an acetonitrile-water medium using LS, sampled DC, DP and cyclic voltammetry. The use of a Britton-Robinson buffer (pH 2.8) containing 20 % of acetonitrile together with the sampled DC mode allows one to analyze binary and ternary mixtures of these antioxidants by applying a PLS type 1 multivariate approach. After optimization of the parameters of the chemometric procedure, the proposed method was validated with synthetic samples and applied for the determination of these antioxidants in different spiked samples of packet soup.

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“…Figure 2a shows the result, which is in good agreement with the literature result for a GC-PE electrode [1]. The peaks marked I/I, and II have been assigned to the oxidations of 1,2-dicarbonyl (reversible) and 1-methoxy-2-carbonyl (irreversible) moieties respectively [1] on the basis of work carried out by Petek et al on catecholamines [15].Next, l-cysteine was added to the solution to a concentration of 15mM, and further CV performed. A third oxidation feature was immediately observed, marked III in Figure 2b.…”

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confidence: 84%

Modifying Glassy Carbon (GC) Electrodes to Confer Selectivity for the Voltammetric Detection of L‐Cysteine in the Presence of dl‐Homocysteine and Glutathione

et al. 2008

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In this communication we report a proof of concept study of the use of cyclic voltammetry with a polyeugenolmodified glassy carbon (GC) electrode to selectively detect l-cysteine in the presence of both dl-homocysteine and glutathione in perchloric acid. The formation of a polyeugenol-modified gold electrode is also reported for the first time.Keywords: Cysteine, Selective electrodes, Eugenol, Glassy carbon DOI: 10.1002/elan.200704151 Eugenol (4-allyl-2-methoxyphenol) has been previously reported to be capable of oxidative polymerization onto Pt and GC electrodes [1,2] and also be used for the selective determination of dopamine in the presence of ascorbic acid [2].The three amino acids cysteine, homocysteine and glutathione are all biologically important, and some are linked as biomarkers for certain diseases/conditions. For example, glutathione depletion has been reported to occur in type II diabetes, age-related macular degeneration [3,4], and HIV [5], whilst high levels of homocysteine are a clinical indicator of the metabolic disorder homocysteinuria [3]. Raised levels of cysteine have been reported in cases of motor neurone disease, Alzheimers and Parkinsons disease [3,6] and also in certain tumors [7,8].The electrochemical detection of thiols, including these amino acids, has been extensively reviewed [9 -11]. The structural similarity of these three thiols makes selective determination often difficult, with established methods relying on careful separation of the compounds before analysis, for example by combining liquid chromatography of capillary electrophoresis with electrochemical detection although this can involve large sample volumes [9]. Electrochemical detection has been reported using pulsed voltammetric methods, mercury electrodes, mediated systems, and derivatized detection [9]. In all cases, the ability to selectively detect one thiol at low concentrations over the others within the medium is the ultimate aim.In this paper we investigate the possibility of forming a polyeugenol (PE)-modified gold electrode and also the performance of GC-PE electrodes in the presence of sulfurcontaining amino acids such as cysteine, homocysteine and glutathione. These compounds were chosen for use in this work due to the well-known interactions between thiols and quinones (and analogously, di-imines) [12 -14], to primarily discover whether this electrode modifier would exhibit any selectivity effects. Any selectivity of one compound over the others may then be further investigated in separate studies to determine the sensitivity of the modified electrode and whether refinements can be made to deliver low detection limits. The close similarity of homocysteine, cysteine, and glutathione towards previous methods [9 -14], provides an incentive for the search for a selective method.First, the electropolymerization of eugenol was performed to form a polyeugenol (PE) film on GC and gold electrodes. In each case, the electrode was placed in a solution of 10 mM eugenol in 0.1 M NaOH and the potential cycled ...

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Anodic oxidation of substituted methoxyphenols. Mass spectrometric identification of methanol formed

Cited by 65 publications

References 5 publications

Preparation and Characterization of a Lignin Modified Electrode

Preparation and Characterization of a Lignin Modified Electrode

Voltammetric Behavior and Simultaneous Determination of the Antioxidants Propyl Gallate, Butylated Hydroxyanisole, and Butylated Hydroxytoluene in Acidic Acetonitrile-Water Medium Using PLS Calibration

Modifying Glassy Carbon (GC) Electrodes to Confer Selectivity for the Voltammetric Detection of L‐Cysteine in the Presence of dl‐Homocysteine and Glutathione

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