Phase behavior in the biologically important oleic acid/sodium oleate/water system

Area of Science:

• Physical Chemistry
• Materials Science
• Biochemistry

Background:

• Understanding the phase behavior of amphiphilic systems is critical in various scientific disciplines.
• Oleic acid and sodium oleate are key components in biological systems and industrial applications.
• The lipolysis of triglycerides produces fatty acids and soaps, influencing dispersion and reaction kinetics.

Purpose of the Study:

• To determine the phase behavior of the oleic acid/sodium oleate/normal saline system.
• To identify the different phases present and their structural characteristics.
• To correlate phase behavior with the ratio of oleic acid to sodium oleate and pH.

Main Methods:

• Visual inspection of samples using crossed polarizers.
• Small Angle X-ray diffraction (SAXS) for phase identification and unit cell determination.
• Modeling of results using an extended Henderson-Hasselbalch equation.

Main Results:

• A rich phase diagram was observed, including reverse micellar, micellar cubic, hexagonal, cubic, and lamellar phases.
• The ratio of oleic acid to sodium oleate was found to dictate the system's pH and consequently its phase behavior.
• The extended Henderson-Hasselbalch equation, incorporating electrostatic potentials, successfully modeled the observed phase behavior.

Conclusions:

• The study elucidates the complex phase behavior of the oleic acid/sodium oleate/saline system.
• The findings provide insights into the dispersion of lipolysis end-products, impacting reaction kinetics.
• This research contributes to a fundamental understanding of lipid-water interactions and their implications in biological and chemical processes.