Determination of the Electrostatic Potential of Oil-in-Water Emulsion Droplets by Combined Use of Two Membrane Potential-Sensitive Dyes

Abstract

The fluorescence behaviors of potential-sensitive dyes including anionic DiBAC4(3) (denoted by dye A), DiSBAC2(3) (dye B), and zwitterionic di-4-ANEPPS (dye C) were studied in oil-in-water (O/W) emulsions. In this study, the equilibrium Galvani potential difference (Δ O W eq) of the O/W-emulsion droplets was controlled by changing the ratio of the concentrations of electrolytes added to the O (=1,2-dichloroethane) and W phases. When using an adequate combination of the dyes, i.e., B and C, we could observe that the ratio of their fluorescence peak intensities was changed from 1.08 to 1.38, depending on the change of (Δ O W eq from 26 to 73 mV. It is desirable to apply this method to study the potentialdependent ion or electron-transfer reactions occurring at vesicles or liposomes, and also to biomembranes.

Electrochemically Modulated Liquid–Liquid Extraction for Sample Enrichment

“…We use instead the theory that was developed in the 1980s by Hung to calculate the Galvani potential difference at equilibrium, ∆  . 30,31 In brief, each ion is distributed between the sample and the organic phase, and for each of them we can define two functions, one for the aqueous phase,  , and one for the organic phase,  , (Eqs. (5) and (6)).…”

“…The interfacial potential was controlled through the dissolution of a common ion in each phase, without the use of electrodes and of a potentiostat, according to the method described in the literature. 30,31 This distribution of the common ion i, with a formal transfer potential Δ o w ϕ i 0 ′, in either phases imposes the interfacial potential, Δ o w ϕ, according to the Nernst-like equation:…”

“…We propose here to combine the vortex-assisted liquid–liquid extraction with the chemical polarization of the interface between two immiscible solutions to prepare samples before chromatographic analysis. The interfacial potential was controlled through the dissolution of a common ion in each phase, without the use of electrodes and of a potentiostat, according to the method described in the literature. , This distribution of the common ion i , with a formal transfer potential Δ o w ϕ i 0′ , in either phases imposes the interfacial potential, Δ o w ϕ, according to the Nernst-like equation: We investigated here the extraction of three biguanide cations: metformin (1,1-dimethylbiguanide), phenformin (phenylethylbiguanide) and phenylbiguanide, whose transfer across the ITIES has already been reported . Molecules of the biguanide family have been used in the treatment of type 2 diabetes since the 1950s .…”

Evaluating the Creaming of an Emulsion via Mass Spectrometry and UV–Vis Spectrophotometry

“…Recent analytical studies of emulsions include evaluations of collapse processes, 1,2 analysis of the interface of droplets, 3−5 and analysis of emulsion products. 6 Turbidity measured by ultraviolet–visible spectrophotometry (UV–vis) has normally been used for the evaluation of emulsion stability.…”

Development of Multiphoton Ionization Time-of-Flight Mass Spectrometry for the Detection of Small Emulsion Droplets

“…Moreover, according to the differences in the density between the droplets and the medium in a continuous phase, dispersed droplets can move to the top or the bottom, which is referred to as creaming or sedimentation, respectively [1]. Many studies concerning emulsions appear in the literature, including recent reports on the coalescence of emulsion droplets [2,3], the monitoring of interfacial lipid oxidation in emulsions [4], an examination into the luminol chemiluminescence profiles of emulsions [5], and a determination of the electrostatic potential of droplets [6].…”