Capillary electrophoresis with linear polymers containing hydrophobic groups for the separation of small molecules

The capillary electrophoretic separation of small charged molecules using linear (non-cross-linked) polymers containing hydrophobic groups was investigated. First, various compositions of linear copolymers, consisting of the water-soluble monomers, acrylamide and N-isopropylacrylamide (IPAAm), were prepared in a running buffer solution, and the effects of alkyl group content in the copolymer chain on the separation of small molecules mere investigated. In order to increase the hydrophobic selectivity, linear copolymers containing more hydrophobic groups (tert-butyl or n-octadecyl) were prepared in methanol as the next step, and were applied to capillary electrophoretic separations after purification. The migration behavior of small molecules in solutions of the copolymers containing hydrophobic groups was different from the separation in a free solution or in polyacrylamide solution. Separations with linear polymers containing hydrophobic groups can be achieved on the basis of the differences in the electrophoretic mobilities and the hydrophobicities of the solutes.