Related Experiment Video
Updated: May 16, 2026
10:32
On-chip Isotachophoresis for Separation of Ions and Purification of Nucleic Acids
Published on: March 2, 2012
Partition coefficients of ionizable solutes in mixed nonionic/ionic micellar systems
Tanja Mehling1, Linda Kloss, Thomas Ingram
1Institute of Thermal Separation Processes, Hamburg University of Technology, Eissendorfer Strasse 38, 21073 Hamburg, Germany. tanja.mehling@tu-harburg.de
Langmuir : the ACS Journal of Surfaces and Colloids
|December 15, 2012
Summary
Mixing ionic and nonionic surfactants enhances solubilization of hydrophobic compounds. Researchers studied mixed micelles (Brij 35/CTAB and Brij 35/SDS) to optimize solute partitioning via pH and composition control.
Area of Science:
- Physical Chemistry
- Colloid and Surface Science
Background:
- Surfactant mixtures, combining ionic and nonionic types, offer synergistic effects for enhanced solubilization of hydrophobic compounds.
- These mixtures reduce the overall surfactant concentration required for effective solubilization, improving efficiency and cost-effectiveness.
Purpose of the Study:
- To investigate the impact of mixed micelle composition (Brij 35/CTAB and Brij 35/SDS) on the partition coefficient (log D(MW)) of acids and bases across the full pH range.
- To evaluate micellar liquid chromatography (MLC) and micellar enhanced ultrafiltration (MEUF) for determining partition coefficients in mixed-micelle systems.
- To assess the predictive capability of the COSMO-RS thermodynamic model for partition coefficients in these mixed systems.
Main Methods:
- Utilized micellar liquid chromatography (MLC) and micellar enhanced ultrafiltration (MEUF) to measure partition coefficients.
- Investigated the influence of pH and mixed micelle composition on solute partitioning.
- Employed the COSMO-RS thermodynamic model to predict partition coefficients and micellar composition.
Main Results:
- Partitioning behavior of solutes is significantly influenced by pH and mixed micelle composition.
- MEUF demonstrated applicability over a broader log D(MW) range compared to MLC.
- The regular solution approximation provided reasonable estimates of micellar composition based on critical micelle concentration (cmc) values.
- COSMO-RS model predictions showed good agreement with experimental partition coefficients.
Conclusions:
- Adjusting pH and mixed micelle composition allows for tailored solute partitioning for diverse applications.
- The COSMO-RS model, when provided with micellar composition, accurately predicts partition coefficients.
- Experimental determination of partition coefficients can be used to refine micellar composition predictions from the COSMO-RS model.
Related Concept Videos
01:14Extraction: Partition and Distribution Coefficients
The distribution law or Nernst's distribution law is the law that governs the distribution of a solute between two immiscible solvents. This law, also known as the partition law, states that if a solute is added to the mixture of two immiscible solvents at a constant temperature, the solute is distributed between the two solvents in such a way that the ratio of solute concentrations in the solvents remains constant at equilibrium.
For extracting a solute from an aqueous phase into an organic...
For extracting a solute from an aqueous phase into an organic...
03:13Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
01:21Factors Affecting Dissolution: Drug pKa, Lipophilicity and GI pH
Drug absorption within the gastrointestinal (GI) tract is a complex process influenced by several critical factors, including the site pH, the drug's dissociation constant (pKa), and the drug's lipophilicity. The GI tract exhibits a pH gradient, with an acidic environment in the stomach and a more alkaline environment in the small intestine. This pH variation directly affects the ionization state of drugs.
A drug's pKa and the pH of the gastrointestinal (GI) tract play crucial roles in drug...
A drug's pKa and the pH of the gastrointestinal (GI) tract play crucial roles in drug...
01:30Micelles
Micelle formation is an intricate process that hinges on the properties of amphiphilic or amphipathic molecules and the conditions of the system in which they are found. Amphiphilic molecules, which have both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, play a critical role in this process.In aqueous environments, these molecules arrange themselves such that their hydrophilic heads are turned towards the water phase, while their hydrophobic tails are oriented away...
01:28Ionic Association
The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.
03:08Electrolytes: van't Hoff Factor
Colligative Properties of ElectrolytesThe colligative properties of a solution depend only on the number, not on the identity, of solute species dissolved. The concentration terms in the equations for various colligative properties (freezing point depression, boiling point elevation, osmotic pressure) pertain to all solute species present in the solution. Nonelectrolytes dissolve physically without dissociation or any other accompanying process. Each molecule that dissolves yields one dissolved...