Analysis of the Phase Diagram and Microstructural Transitions in Phospholipid Microemulsion Systems Using High-Resolution Ultrasonic Spectroscopy

Abstract

In the present work, high-resolution ultrasonic spectroscopy was applied to analyze a pseudoternary phase diagram for mixtures consisting of water/isopropyl myristate/Epikuron 200 and a cosurfactant (n-propanol). Changes in the ultrasonic velocity and attenuation in the megahertz frequency range were measured in the course of titration of the oil/surfactant/cosurfactant mixture with water at 25 degrees C. The ultrasonic titration profiles showed several phase transitions in the samples, which allowed the construction of an "ultrasonic" phase diagram. Quantitative analysis of the ultrasonic parameters enabled the characterization of various phases (swollen micelles, microemulsion, coarse emulsion, and pseudo-bicontinuous) as well as the evaluation of the state of the water and the particle size. The particle size obtained for the microemulsion region ranged from 5 to 14 nm over the measured concentrations of water/isopropyl myristate/Epikuron 200 and n-propanol, which agreed well with the previous literature data.

Ultrasonic Characterisation of W/O Microemulsions - Structure, Phase Diagrams, State of Water in Nano-Droplets, Encapsulated Proteins, Enzymes

“…Applications of ultrasonic scattering theories allow calculations of sizes of dispersed particles from the measured values of attenuation and the physical parameters of the continuous medium and the particles. The obtained sizes in microemulsions are in good agreement with the results of other techniques (Hickey et al, 2006(Hickey et al, , 2010.…”

“…The ultrapure water (Millipore Super-Q-System) with the conductivity of 18.2 MΩ・cm −1 was used in sample preparation. Details of preparations of emulsions were described previously (Hickey et al, 2006, Hickey et al, 2010. : n-propanol (1:1, w/w)] -38% (w/w); -water -24% (w/w).…”

“…Application of ultrasonic spectroscopy in microemulsion systems in the past was often limited by the resolution of the measurements, requirements of large sample volumes and limited range of measuring regimes. Introduction of high-resolution ultrasonic spectroscopy (HR-US) (Buckin & O'Driscoll, 2002;Buckin et al, 2003;Kudryashov et al, 2000;Buckin et al, 2002) overcame the above limitations and allowed applications of this technique for analysis of microemulsion structure and phase diagrams (Hickey et al, 2006) in a simple automatic or manual titration regimes. The technique is based on precision measurements of ultrasonic velocity and attenuation in the frequency range 1 to 20MHz.…”

“…The technique is based on precision measurements of ultrasonic velocity and attenuation in the frequency range 1 to 20MHz. In w/o microemulsions it provided characterization of transitions between different phases, such as swollen micelles, microemulsion, coarse emulsion, liquid crystals, and evaluation of microstructural attributes of the phases, as well as characterisation of the state of water in emulsion droplets and the size of the droplets (Hickey et al, 2006(Hickey et al, , 2010. Previous applications of ultrasonic spectroscopy for analysis of microemulsions demonstrated an exceptional sensitivity of ultrasonic parameters to the structural characteristics of microemulsions and to the state of its components.…”

Monitoring Oxidation Behavior of [C70]Fullerene by Ultrasonic Spectroscopy

“…[5][6][7][8] Ultrasonic spectroscopy has been used successfully to observe many types of phase transitions in the liquid state. [9][10][11][12][13][14][15] The two main parameters measured by ultrasonic spectrometry are the attenuation and the velocity of the waves. Ultrasonic attenuation is determined by the energy losses in the ultrasonic wave propagating through the sample.…”