Low-Electroosmotic-Mobility Coatings for ASTP Free-Fluid Electrophoretic Separation

The Apollo 16 Electrophoresis Experiment demonstrated the need for a low-electroosmotic-mobility coating in a free-fluid electro-phoretic separation.1 The photographs of the experiment showed parabolic particle profiles that are characteristic of electroosmosis in the cell and which render a practical separation impossible. These paraboiic particle profiles were in good agreement with theoretical profiles calculated assuming an electroosmotic mobility of the cell walls equal to −lOμm cm/volt sec.2 Therefore, a major effort was initiated to develop a coating that would reduce the zeta potential at the cell-wall/liquid interface to zero or near-zero, to eliminate the driving force responsible for electroosmotic flow in the presence of an applied electrical potential. The initial work was directed towards the electrokinetic behavior of different coatings on a variety of surfaces in the presence of different buffer systems because neither the buffer nor the electrophoresis cell material were decided upon until very late in the development of the ASTP experiment.