Capillary Electrochromatography for Analysis of Small Polar Molecules Using Etched Chemically Modified Capillaries

Open tubular capillary electrochromatography (OTCEC) is an analytical technique that incorporates features of high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Polyimide capillaries can be etched to increase the low loading capacity, a potential drawback of CE. The etching process also changes the surface matrix of the capillary, thereby altering its electroosmotic properties. In addition, silanization and hydrosilation reactions exchange the silanol surface for silica hydride and incorporate a novel bonded stationary phase, resulting in unique electroosmotic properties and analyte-stationary phase interaction. In this study, the electrochromatographic behavior of certain amines, amino acids, nucleotides, and neurotransmitters was investigated as a function of electroosmotic flow, electrophoretic mobility, and chromatographic interaction with the bonded phase. It was determined that etched chemically modified capillaries provide a viable, and often superior, alternative to traditional capillaries with respect to efficiency and resolution