Capillary electrophoresis study on the evolution of phase of AOT/TX-100 mixed micelles

Abstract

Capillary electrophoresis (CE) coupled with the contactless conductivity detector (CD) was applied to characterize the evolution of the phase of mixed micelles AOT and TX-100 (AOT/TX-100) based on 0.026 M AOT. Three states of AOT/TX-100 mixed micelles were established due to the evolution of the micellar phase of 0.026 M AOT/(0 – 0.11 M) TX-100 with increasing TX-100 concentration, i.e., a metastable → cluster → TX-100-rich. The cluster was found to be an intermediate state between AOT-rich and TX-100-rich AOT/TX-100 micelles. Add-in phenomena were visualized; the co-existence of two micelles, and related to this, the presence of two peaks of Na⁺ counterions on an electropherogram. In the second part of the work, the microreactor system was introduced to control the evolution of the AOT/TX-100 phase. Two options were examined, which rely on the difference in migration of two micelles, leading to micelles overlapping and merging during a run, with the consequence of the generation of a new micelle. The system was tested on an intermediate state, i.e., cluster, and independently, two states of AOT/TX-100 micelles; AOT-rich and TX-100-rich, respectively, were generated in a controllable manner. A comparison of electrophoretic data for micelles, in terms of mobility, shows a drastic decrease in AOT/TX-100 polydispersity for micelles generated in the microreactor system. At the end of the report, we briefly compared the AOT/TX-100 and SDS/TX-100 phase, reported recently, from the perspective of CE/C⁴D.