Characteristics of electroosmotic flow in capillary electrophoresis in water and in organic solvents without added ionic species

Abstract

Although proper buffering is essential for repeatable separations in capillary electrophoresis, electroosmotic flow can be developed in many solvents without the addition of buffer components. In this study we detected electroosmotic flow in fused silica capillary in the following solvents without the addition of ionic species: water, deuterium oxide, acetonitrile, acetone, 2-butanone, formamide, N-methylformamide, N,N-dimethylformamide, methanol, ethanol, 1-propanol, dimethyl sulfoxide, ethyl acetate, tetrahydrofuran, and morpholine. The electroosmotic flow was in the range of 3.4×10−9–1.8×10−m2/V s. About 100 times weaker electroosmosis was detected in glacial acetic acid. We also detected electroosmotic flow in N-methylacetamide, which is solid at room temperature (melting range 28–30°C). No electroosmotic flow was found in inert solvents such as n-hexane and chloroform. The zeta potential of the fused silica capillary was calculated for the solvents where electroosmotic flow was found. The zeta potential of the capillary wall was also studied in water–methanol mixtures, where it has a maximum at about 40% methanol concentration. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 199–208, 1999