PubMed · 13526686
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J KOHN. 1958-03-22. A micro-electrophoretic method.. https://doi.org/10.1038/181839a0
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We studied the effects of the degree of ionization(alpha) and the surfactant concentration (C(d)) on the micelle-vesicle transition in salt-free oleyldimethylamine oxide (OlDMAO) aqueous solutions by the dynamic light scattering (DLS), the hydrogen ion titration, the small angle neutron scattering (SANS), the electrophoretic light scattering (ELS) and viscoelastic measurements. From the study of ionization effects, the micelle-vesicle transition was recognized as a change of aggregate size by the DLS measurement; however, the micelle-vesicle transition was not detected both in the ELS measurement and the hydrogen ion titration, suggesting that the electric properties of the worm-like micelles and the vesicles are very similar despite a large difference of shapes between them. From the results of the SANS, the DLS and the viscosity measurements, it was suggested that a concentration-dependent micelle-vesicle transition took place around C(p)=10 mmolkg-1 for the solutions at alpha=0.5. In the concentration-range 10 mmolkg-1<C(d)<150 mmolkg-1, the micelles and the vesicles coexisted. In the concentration region (C(d) = 10-50 mmolkg-1), the vesicle size increased with the surfactant concentration.
The boundary effect on the electrophoresis of particles covered by a membrane layer is discussed by considering a spherical particle in a spherical cavity under the conditions where the effect of double-layer polarization can be significant. The influence of the key parameters of the system under consideration on the electrophoretic mobility of a particle is investigated. These include the surface potential; the thickness of the double layer; the relative size of the cavity; and the thickness, the fixed charge density, and the friction coefficient of the membrane layer. The fixed charge in the membrane layer of a particle is found to have a significant influence on its electrophoretic behavior. For instance, depending upon the amount of fixed charge in the membrane layer, the mobility of a particle may exhibit a local minimum as the thickness of the double layer varies.
This feasibility study deals with column switching in zone electrophoresis (ZE) separations on a column coupling (CC) chip. The column switching implemented into the ZE separations an on-chip sample clean up applicable for both the multicomponent and high salinity samples. In addition, complemented by different separation mechanisms in the coupled columns (channels), it provided benefits of two-dimensional separations. Properly timed column switching gave column-to-column transfers of the analytes, characterized by 99-102% recoveries, delivered to the second separation stage on the chip the analyte containing fractions contaminated only with minimum amounts of the matrix constituents. A diffusion driven transport of the matrix constituents to the second channel of the chip (due to direct contacts of the electrolyte solutions in the bifurcation region), representing 0.1-0.2% of the loaded sample constituents, was found to accompany the sample clean up performed on the CC chip. This source of potential disturbances to the separation in the second channel, however, is not detectable in a majority of practical situations. With respect to a 900 nl volume of the sample channel on the CC chip, the electric field and isotachophoresis (ITP) stackings were employed to minimize the injection dispersion in the separations and concentrate the analytes. Here, the column switching, removing a major part of the stacker from the separation system, provided a tool effective in a control of the destacking of analytes. Highly reproducible ZE separations as attained in this work also for the chip-to-chip and equipment-to-equipment frames can be ascribed, at least in part, to suppressions of electroosmotic and hydrodynamic flows of the solutions in which the separations were performed.