Solution microstructure and electrochemical reactivity. Effect of probe partitioning on electrochemical formal potentials in microheterogeneous solutions

Myers, Stephanie A.; Mackay, Raymond A.; Brajter-Toth, Anna

doi:10.1021/ac00071a019

Cited by 33 publications

(36 citation statements)

References 11 publications

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“…Moreover, water molecules must break the nonpolar barrier around the droplets and diffuse to the surface of the electrode before the charge transfer reaction takes place. 23 In the cathodic region, water reduction should be facilitated by a migration component towards the electrode due to the net positive charge located into the water droplets, which can explain that no reduction wave is observed in the experimental conditions of this study. On the other hand, assuming that for the water reduction reaction the diffusion coefficient value D w/o will be closer to the one found from DLS measurements, the limiting current will be theoretically around 6 nA, calculated from equation (1) using D w/o = 5.4 x 10 -8 cm 2 s -1 (see Table 2).…”

mentioning

confidence: 71%

“…23 This hypothesis could also explain the diffusion coefficient value found for Fc in ME, higher than the value found for D w/o , in spite of the Fc much lower concentration.…”

Section: Electrochemical Measurementsmentioning

confidence: 86%

“…Assuming that the diffusion coefficient value for species in the droplets is the same as the one of the droplets 23 these results may be explained, in part, by the net positive charge carried by a fraction of the droplets as discussed above. 36 Consequently, its transport to the surface of the electrode is hindered by an unfavorable migration component.…”

Section: Electrochemical Measurementsmentioning

confidence: 89%

“…Electroanalytical techniques may provide valuable information concerning the structural evolution, interparticle interaction and transport data, 17,23,24 yet there are very few studies employing electroanalytical methods in ME of water in vegetable oils. In this sense a Pt disk ultramicroelectrode (ume), allows to carry out linear voltammetric 25 measurements in resistive media 26 as is the case in this study.…”

Section: Introductionmentioning

confidence: 99%

“…The transparent to the turbid state can be brought about by variations of temperature, pressure or composition of the mixture and the transition point, the point of incipient phase separation, is the cloud point. 22 When the sample reaches the cloud point temperature, the sample gets turbid and ceases to show the transparency which characterizes a ME, a new phase starting to separate.Electroanalytical techniques may provide valuable information concerning the structural evolution, interparticle interaction and transport data, 17,23,24 yet there are very few studies employing electroanalytical methods in ME of water in vegetable oils. In this sense a Pt disk ultramicroelectrode (ume), allows to carry out linear voltammetric 25 measurements in resistive media 26 as is the case in this study.…”

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confidence: 99%

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Water in soybean oil microemulsions as medium for electrochemical measurements

Mendonça¹,

Bica²,

Piatnicki³

2003

J. Braz. Chem. Soc.

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Microemulsões de água em óleo de soja (w/o ME) foram preparadas com dodecil sulfato de sódio (SDS) como surfactante e com os álcoois amílico ou isoamílico, como co-surfactantes. A composição 40,0% de óleo, 43,2% de álcool, 10,8% de SDS e 6,0% de água, em massa, na razão 1:4 [SDS]: [álcool], apresentou a maior estabilidade termodinâmica. O tamanho das gotículas e seu coeficiente de difusão nas microemulsões, D w/o , foram determinados por medidas de espalhamento de luz dinâmico (DLS). As reações de oxidação de ferroceno (Fc) e de água, e a redução de ácido oleico foram observadas nas ME por voltametria em um ultramicroeletrodo (ume) de disco de Pt. Os valores de D w/o determinados a partir de medidas eletroquímicas são menores do que os calculados a partir daquelas por DLS. Isto indica que a oxidação da água requer a difusão para o eletrodo tanto das gotículas como das moléculas de água nelas contidas. Os resultados evidenciam a possibilidade de determinação de analitos em óleos vegetais por métodos eletroanalíticos.Microemulsions of water in soybean oil (w/o ME) were prepared with sodium dodecyl sulfate (SDS) as surfactant and amyl or isoamyl alcohol, as co-surfactants. Microemulsions containing 40.0% oil, 43.2% alcohol, 10.8% SDS and 6.0% water in weight, in the ratio 1:4 [SDS]: [alcohol] showed the highest thermodynamic stability. The aqueous droplet size and its diffusion coefficient D w/o in the ME were determined through dynamic light scattering (DLS). Voltammetric measurements in the ME at a Pt disk ultramicroelectrode (ume) evidenced the oxidation of both water and ferrocene (Fc), and the reduction of oleic acid. The D w/o values calculated from the limiting current being lower than the ones obtained from DLS indicate that water oxidation probably requires diffusion towards the electrode of both the droplets and the water molecules from inside the droplets. The results show that electroanalytical determinations can be carried out in w/o ME. Keywords: microemulsions, soybean oil, voltammetry, ferrocene, oleic acid IntroductionEquilibria in water-oil interfaces have been studied in order to quantify solvent extraction as well as charge transfer processes. In this sense new analytical methodologies such as slow extrusion of water into a nonaqueous phase (and vice-versa) through a capillary, 1 the use of micrometric electrodes 2-3 and of microemulsions 4,5 (ME) have been proposed recently. Besides a significant decrease in costs and toxicity due to the decrease in organic solvents consumption, 6-8 water in oil ME allow to carry out electrochemical measurements due to the enhanced electrical conductivity imparted to the system by the presence of water.Microemulsions are thermodynamically stable systems composed of water, oil and surfactant, and, in some cases, an alcohol can be added as co-surfactant. 9-12 Their behavior is similar to the one of polar organic solvents and, although apparently homogeneous under visual observation, ME are actually microheterogeneous (perhaps nanoheterogeneous would be a better...

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mentioning

confidence: 71%

“…23 This hypothesis could also explain the diffusion coefficient value found for Fc in ME, higher than the value found for D w/o , in spite of the Fc much lower concentration.…”

Section: Electrochemical Measurementsmentioning

confidence: 86%

Section: Electrochemical Measurementsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Water in soybean oil microemulsions as medium for electrochemical measurements

Mendonça¹,

Bica²,

Piatnicki³

2003

J. Braz. Chem. Soc.

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Electrode Potentials

Петрий

Tsirlina

2002

Encyclopedia of Electrochemistry

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The sections in this article are Introductory Remarks External and Internal Potentials Electromotive Force ( emf ) and Gibbs Energy of Reaction Diffusion Potential Drop Classification of Electrodes Membrane Electrodes Standard Potentials Specific Features of Certain Reference Electrodes Values of Redox Potentials Potential Windows Experimental Techniques Effects of Ion Pairing Absolute Electrode Potential The Role of Electric Double Layers Conclusion

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Redox Chemistry of Heteropolyacid Microemulsions

et al. 2014

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Insight from electroanalysis studies of dense fluid phases (known as “third” phases) in the Keggin heteropolyacid tri‐n‐butyl phosphate (TBP) system is provided. The differences between the H3PW12O40 and H4SiW12O40 redox chemistry in the third phases and in bulk aqueous electrolytes reflect the differences in the formal charge of the protonated acid solvates of TBP in the low dielectric organic media and the deprotonated anions in the high dielectric aqueous media. The faradaic W‐based redox activity leading to heteropoly blue entities drives concerted proton transfer across the organic‐analyte–aqueous‐electrolyte phase boundary in both the heteropolyacid microemulsions (formed by solvent extraction) and the molecular liquids (formed by dissolution) to maintain charge neutrality in the organic phases. This study of heteropolyacid third phases complements the emerging field of mesoscale sciences with polyoxometalates and their electrochemical properties.

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Solution microstructure and electrochemical reactivity. Effect of probe partitioning on electrochemical formal potentials in microheterogeneous solutions

Cited by 33 publications

References 11 publications

Water in soybean oil microemulsions as medium for electrochemical measurements

Water in soybean oil microemulsions as medium for electrochemical measurements

Electrode Potentials

Redox Chemistry of Heteropolyacid Microemulsions

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