Non-aqueous capillary electrophoresis using non-dissociating solvents - Application to the separation of highly hydrophobic oligomers

The application of non-aqueous capillary electrophoresis for the separation of very hydrophobic oligomers has been studied. N-Phenylaniline oligomers having degrees of polymerisation (n) of 2, 4, 6, and 8 were taken as model compounds. Capillary electrophoresis could be performed using a mixture of non-aqueous solvents with a high percentage of solvents with a low dielectr ic constant. These solvents, such as tetrahydrofuran (THF), chloroform or d ichloromethane, are needed to solubilise the hydrophobic solutes in the ele ctrolyte. The composition of the solvent mixture and the nature of the acid added to the electrolyte, which is needed to obtain electrophoretic motion of the N-phenylaniline oligomers, are discussed in detail. Next, other par ameters such as ionic strength, injection time, electric field, and tempera ture were investigated too and their influence on the separation is discuss ed as well. The existence of a reversed (anodic) electroosmotic flow in a f used-silica capillary containing a THF-methanol mixture under acidic condit ions is reported. (C) 2001 Elsevier Science B.V. All rights reserved.