The diameter of the oil droplets are below 10nm so they do not scatter white light which means that the microemulsion is optically transparent. Use of a microemulsion containing ionic surfactants allows chromatographic separation to be obtained as solutes can partition between the oil droplet and the aqueous buffer phase. Water-insoluble compounds will favour inclusion into the oil droplet rather than into the buffer phase. This situation allows partitioning of the solute between the oil and water phases in a chromatographic fashion. Hydrophobic solutes will reside more frequently in the oil droplet than water-soluble solutes.
Solutes chromatographically interact with the micelles to achieve separation.
The oil droplet is coated with SDS surfactant molecules making the droplet negatively charged. The C 12 alkylchain of the surfactant penetrates into the oil droplet whilst the negatively charged hydrophilic sulphate groups resides in the surrounding aqueous phase. Charge repulsion of the negatively charged sulphate group on the SDS prevents highly efficient packing and prevents formation of an emulsion as the surface tension cannot be sufficiently reduced. The co-surfactant bridges the oil and water interface and further reduces the surface tension of the system to zero. Figure 1 provides a schematic of the emulsion droplet showing the short chain alcohol, SDS, the octane droplet and the sodium ions surrounding the droplet.