ITP in dynamically double-coated fused-silica capillaries

Abstract

Bidirectional ITP in fused-silica capillaris double-coated with Polybrene and poly-(vinylsulfonate) is a robust approach for analysis of low-molecular-mass compounds. EOF towards the cathode is strong (mobility >4.0 × 10-8 M2/Vs) within the entire pH range investigated (2.40-8.08), dependent on ionic strength and buffer used and, at constant ionic strength, higherat alkaline pH. Electrokinetic separations and transport in such coated capillaries can be described with a dynamic computer model which permits the combined simulation of electrophoresis and electroosmosis in which the EOF is predicted either with a constant (i.e. pH- and ionic strength-independent) or a pH- and ionic strength-dependent electroosmotic mobility. Detector profiles predicted by computer simulation agree qualitatively well with bidirectional isotachopherograms that are monitored with a setup comprising two axial contactless conductivity detectors and a UV absorbance detector. The varying EOF predicted with a pH- and ionic strength-dependent electroosmotic mobility can be regarded as being realistic. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.