ITP in dynamically double-coated fused-silica capillaries

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrochemistry

Background:

• Bidirectional isotachophoresis (ITP) in fused-silica capillaries coated with Polybrene and poly-(vinylsulfonate) is effective for analyzing low-molecular-mass compounds.
• Strong electroosmotic flow (EOF) towards the cathode is observed across a wide pH range (2.40-8.08), influenced by ionic strength and buffer type, increasing at alkaline pH.

Purpose of the Study:

• To develop and validate a dynamic computer model for simulating electrokinetic separations and transport in bidirectional ITP.
• To investigate the prediction of EOF using both constant and pH/ionic strength-dependent electroosmotic mobility within the model.

Main Methods:

• Utilized fused-silica capillaries double-coated with Polybrene and poly-(vinylsulfonate) for bidirectional ITP.
• Employed a dynamic computer model to simulate combined electrophoresis and electroosmosis.
• Monitored detector profiles using two axial contactless conductivity detectors and a UV absorbance detector.

Main Results:

• The dynamic computer model successfully predicted detector profiles that qualitatively matched experimental bidirectional isotachopherograms.
• The model's ability to predict varying EOF based on pH and ionic strength was deemed realistic.
• EOF mobility was found to be strong (>4.0 x 10(-8) m(2)/Vs) and dependent on experimental conditions.

Conclusions:

• Bidirectional ITP in specially coated capillaries, coupled with a dynamic simulation model, provides a robust analytical method.
• The developed computer model accurately simulates electrokinetic transport phenomena, including pH- and ionic strength-dependent EOF.
• This approach enhances the understanding and prediction of complex separation behaviors in capillary electrophoresis.