Interaction of substituted benzoic acids with polysorbate 20 micelles

Area of Science:

• Physical Chemistry
• Pharmaceutical Sciences
• Colloid and Surface Chemistry

Background:

• Understanding drug solubility is crucial for formulation development.
• Polysorbate 20 is a common non-ionic surfactant used in pharmaceutical formulations.
• The solubility of weakly acidic drugs like benzoic acid is pH-dependent.

Purpose of the Study:

• To investigate the equilibrium solubility of substituted benzoic acids in polysorbate 20 solutions.
• To determine the influence of surfactant concentration and solubilizate polarity on solubility.
• To quantify the interaction between benzoic acid molecules and polysorbate 20 micelles.

Main Methods:

• Solubility measurements of substituted benzoic acids at controlled pH using a pH-stat assembly.
• Systematic variation of polysorbate 20 concentrations.
• Analysis of solubility data to calculate partition coefficients.

Main Results:

• A linear correlation was observed between benzoic acid solubilization and polysorbate 20 concentration.
• Increased solubilizate polarity led to enhanced benzoic acid solubility.
• Partition coefficients for ionized and unionized benzoic acid molecules were determined, showing a linear relationship with functional group pi values.

Conclusions:

• Polysorbate 20 effectively enhances the solubility of substituted benzoic acids.
• Solubilization is influenced by both surfactant concentration and the physicochemical properties of the benzoic acid derivatives.
• The study provides quantitative insights into drug-micelle interactions, valuable for pharmaceutical formulation design.