Voltammetric determination of weak bases based on oxidation of α-tocopherol in an unbuffered solution

Taguchi, Junichi; Ohtsuki, Sanae; Kusu, Fumiyo

doi:10.1016/s0022-0728(03)00351-6

Cited by 26 publications

(18 citation statements)

References 14 publications

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“…There is no doubt that the ion formed is stronger solvated than the molecular form of trolox. A similar effect was observed by Kusu and co-workers [21,22] when a base was added to the unbuffered solution of a-tocopherol in methanol.…”

Section: Voltammetry In Alkaline Solutionssupporting

confidence: 80%

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Karbarz¹,

Małyszko²

2008

Electroanalysis

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Electrochemical oxidation of trolox on carbon electrodes was investigated by means of some voltammetric techniques in methanol and ethanol solutions in the presence of an excess of acid or base. The oxidation occurs according to EEC mechanism, i.e. in two quasireversible one-electron steps yielding the corresponding phenoxyl radical and, subsequently, phenoxonium cation. Phenoxonium ion decays because of a pseudo-first order follow-up chemical reaction with nucleophiles. The electrochemical behavior of trolox is strongly influenced by the surrounding environmental conditions. In acidic solutions, a single two-electron anodic wave was observed. The presence of a strong base drastically improves the stability of the intermediate, phenoxyl radical. Under these conditions, the twoelectron wave was found to split into its one-electron components over a range of scan rates. The resolution is much distinct in ethanol. Simulations with DigiSim software were used to fit the cyclic voltammograms in order to estimate thermodynamic and kinetic data for the reaction mechanism studied.

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Section: Voltammetry In Alkaline Solutionssupporting

confidence: 80%

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Karbarz¹,

Małyszko²

2008

Electroanalysis

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“…The mechanism for the electrode oxidation of A-TOH in the presence of weak base was reported by Taguchi, et al 19 The effects of nucleophiles and weak base molecules on the electrochemical oxidation of A-TOH was explained, based on the following EC pathway involves a two-electron transfer coupled with a one-proton transfer giving a phenoxonium ion: where ROH is a nucleophile such as a solvent molecule. The protons produced by oxidation of A-TOH at the electrode surface are likely to be neutralized by the weak base, a nucleophile stronger than the solvent molecule.…”

Section: Voltammetric Determination Of Ammoniamentioning

confidence: 99%

“…And, the half-peak potential (E p/2 ) of prepeak shifted to a more negative value accompanied by a decrease in the pK b . 19 Thus, the occurrence of the prepeak is considered in terms of the acceleration of the first electron transfer reaction of A-TOH. Presumably, ammonia, being a nucleophile, would form an intermediate complex with a phenoxonium ion, and would consequently accelerate the first electron transfer reaction.…”

Section: Voltammetric Determination Of Ammoniamentioning

confidence: 99%

“…Using a conductivity sensor, the determination of ammonia in exhaled breath has been previously reported, 18 but other electroalanytical methods such as amperometric and/or coulometric detection have never been applied to the analysis of exhaled breath. Our preliminary study showed that the flow injection analysis with electrochemical detection (FIA-ECD) by means of the voltammetric oxidation of A-tocopherol (5,7,8-trimethyltocol, A-TOH) 19 was applicable for determining ammonia in pharmaceutical preparations. 20 However, the reported FIA-ECD was inapplicable for the determination of exhaled breath ammonia, because the sensitivity was poor and there was no method provided for sample preparation to the analysis of exhaled breath.…”

Section: Introductionmentioning

confidence: 99%

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Determination of Ammonia in Exhaled Breath by Flow Injection Analysis with Electrochemical Detection

et al. 2012

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Flow injection analysis with electrochemical detection (FIA-ECD) using α-tocopheol (α-TOH) as a reagent was developed for determining ammonia in exhaled breath. An ethanol-water (4:1, v/v) mixture containing 3 mM α-TOH and 50 mM NaCl was used as the carrier solution. The FIA response at +0.70 V vs. Ag/AgCl in the flow cell was linear over a range of the ammonia concentration from 0.11 to 1.1 ppmv (r = 0.999, n = 7). The lower limit of detection for ammonia was 130 pg (S/N = 3), and the relative standard deviation (RSD) was 2.1% (17 ng, n = 10). The collected exhaled breath in a Tedlar ® bag was mixed with water containing NaCl to dissolve ammonia in exhaled breath, and then it was diluted with ethanol containing α-TOH to the same composition of the carrier solution to be injected into the FIA-ECD. The present FIA-ECD method required simple sample preparation and was applied to the determination of ammonia in exhaled breath from a healthy human and gerbils.

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“…For the analysis of these H 2 -receptor antagonists, several methods, such as titration (1,2), HPLC (3)(4)(5), high-performance thin-layer chromatography (HPTLC) (6), spectrophotometry (7)(8)(9)(10), capillary electrophoresis (CE) (11)(12)(13), voltammetry (14,15) and chemiluminescence (CL) (16) have been reported.…”

Section: Introductionmentioning

confidence: 99%

A new sensitive flow‐injection chemiluminescence method for the determination of H₂‐receptor antagonists

et al. 2007

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Based on the chemiluminescence (CL) intensity generated from the potassium ferricyanide [K(3)Fe(CN)(6)]-rhodamine 6G system in sodium hydroxide (NaOH) medium, a new sensitive flow-injection chemiluminescence (FI-CL) method has been developed, validated and applied for the determination of three kinds of H(2)-receptor antagonists: cimetidine (CIMT), ranitidine (RANT) hydrochloride and famotidine (FAMT). Under the optimum conditions, the linear range for the determination was 1.0 x 10(-9)-7.0 x 10(-5) g/ml for CIMT, 1.0 x 10(-9)-5.0 x 10(-5) g/mL for RANT hydrochloride and 5.0 x 10(-9)-7.0 x 10(-5) g/mL for FAMT. During 11 repeated measurements of 1.0 x 10(-6) g/mL sample solutions, the relative standard deviations (RSDs) were all <5%. The detection limit was 8.56 x 10(-10) g/mL for CIMT, 8.69 x 10(-10) g/mL for RANT hydrochloride and 2.35 x 10(-9) g/mL for FAMT (S:N = 3). This method has been successfully implemented for the analysis of H(2)-receptor antagonists in pharmaceuticals.

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Voltammetric determination of weak bases based on oxidation of α-tocopherol in an unbuffered solution

Cited by 26 publications

References 14 publications

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Determination of Ammonia in Exhaled Breath by Flow Injection Analysis with Electrochemical Detection

A new sensitive flow‐injection chemiluminescence method for the determination of H₂‐receptor antagonists

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Voltammetric determination of weak bases based on oxidation of α-tocopherol in an unbuffered solution

Cited by 26 publications

References 14 publications

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Voltammetric Behavior of Trolox in Methanol and Ethanol Solutions

Determination of Ammonia in Exhaled Breath by Flow Injection Analysis with Electrochemical Detection

A new sensitive flow‐injection chemiluminescence method for the determination of H2‐receptor antagonists

Contact Info

Product

Resources

About

A new sensitive flow‐injection chemiluminescence method for the determination of H₂‐receptor antagonists