Open tubular capillary electrochromatography in etched, chemically modified 20 mu m ID Capillaries

Fused silica capillaries with an I.D. of 20 mu m are etched and then chemic ally modified by the silanization/hydrosilation method to attach an octadec yl moiety for use in electrokinetic chromatography. The etched capillaries after chemical modification are shown to have an anodic electroosmotic flow below pH 4.5. In comparison to bare 20 mu m capillaries and unetched but c hemically modified 20 mu m capillaries, the etched C-18 fused silica tubes show better separation of mixtures of lysozymes and cytochrome c's under id entical conditions of buffer, pH and applied voltage. It was also demonstra ted that this open tubular approach to capillary electrochromatography was amenable to a number of different types of basic compounds ranging in size from typical small amines to biomolecules. As expected, pH is an important variable that must be controlled in order to obtain an optimized separation . Reproducibility studies verify the stability of the silicon-carbon linkag e produced in this modification method so that column lifetimes of at least 300 injections can be expected. (C) 1999 Elsevier Science B.V. All rights reserved.