Separation of polyelectrolytes of variable compositions by free-zone capillary electrophoresis

Capillary electrophoresis (CE) of a series of random copolymers of the ionic monomer, sodium 2-acrylamido-2-methylpropanesulfonate (AMPS), and the nonionic monomer, acrylamide (AAm), was carried out. The absolute value of the electrophoretic mobility mu(E) increases as expected with AMPS content. However, mu(E) clearly shows a discontinuity when the reduced polymer linear charge density, xi, becomes unity. This phenomenon is a confirmation of Manning's counterion condensation theory. It is concluded that free-zone CE can be used to separate and characterize charged copolymers below xi=1.