Critical Micelle Concentration Determination with Non-contact RF Dielectric Impedancemetry for Surfactants in Solution

Surfactants are a widely used family of polar molecules which possess both hydrophilic and lipophilic parts. Their polar conformation properties make them useful in a variety of applications, including emulsion stabilization, drug delivery, and detergency. In a colloidal solution, surfactant molecules self-aggregate to form micelles which can be used to reduce the surface tension of oil-water interfaces in emulsions. The Critical Micelle Concentration (CMC) is the point at which the surfactant undergoes self-aggregation, forming a separate phase that modifies the electrical and mechanical properties of the colloidal solution. From a kinematic perspective, it is related to the critical stage at which the droplets are stabilized by the surfactant molecules. The CMC can be estimated using a variety of techniques. Each method possesses its own inherent limitations, which can result in approximations, especially when dealing with mixtures of multiple surfactants and polymers. This article presents a novel contactless radiofrequency inductive technique for measuring the CMC of surfactants in complex fluids. This method is based on the monitoring of the dielectric properties of the complex medium. The effectiveness of the technique is validated using known surfactants according to literature and conventional methods. The capacity of this technique to provide consistent and accurate CMC values, even for complex solutions comprising multiple surfactants, is demonstrated.