Capillary electrophoresis (CE) presents a widely applicable technique in analytical chemistry, as it exhibits high resolution, short analysis times and extraordinary small sample and solvent consumption. Typically, capillaries made of fused silica are employed, since surface chemistry is sufficiently understood and manufacturing technologies are well developed. However, this material suffers from several inherent disadvantages. In particular, the electroosmotic flow (EOF) is highly dependent on the pH of the carrier electrolyte. As a result, often background electrolytes favourable for separating the analytes cannot be used, as the EOF is not suitable.

In this study, materials different from fused silica were investigated regarding their applicability as separation capillaries in CE. Capillaries made of polycarbonate (PC), polyphenylsulfone (PPSU) and perfluoroalkoxy (PFA) were studied. The characterisation included an investigation of the dependence of the EOF on the composition of the background electrolyte. Furthermore, possibilities of chemically modifying the inner surface of the polymer capillary were examined such as the sulfonation of PPSU capillaries. This treatment led to a relatively high EOF that was independent of pH and allowed the separation of analytes with low electrophoretic mobility under acidic pH conditions. Under such conditions a simple and straightforward separation of several benzoic acid derivatives including positional isomers could be demonstrated.