Overview
This document explains the functional mechanism behind Zero‑Flow™ CE capillaries. While they start as standard fused silica capillaries, the inner surface is modified with a covalently bonded linear polyacrylamide (LPA) coating. LPA is “effectively neutral,” containing no ionizable groups, which prevents the formation of electroosmotic flow even under high voltage. This design ensures predictable analyte migration based solely on electrophoretic mobility.
The post also distinguishes the inner LPA coating from the outer polyimide coating, which provides structural durability but has no influence on electroosmotic flow or electrophoretic behavior.
Zero‑Flow CE Capillary Mechanism
Zero‑Flow™ CE capillaries begin as standard bare fused silica capillaries, but the inner surface is chemically modified so that it will not generate electroosmotic flow (EOF).
The inner wall is covalently bonded with linear polyacrylamide (LPA). LPA contains no ionizable functional groups, which makes the surface effectively neutral. With no positive or negative charge to generate zeta potential, EOF is not produced, even when full current is applied across the capillary.
Important Distinction
Polyacrylamide (the inner coating) should not be confused with polyimide, the outer coating found on all CE capillaries.
- Polyacrylamide (inner): Controls electrophoretic behavior, eliminates EOF
- Polyimide (outer): Provides mechanical strength and flexibility; does not influence EOF or separation
Click HERE for Zero‑Flow Capillary ordering information and pictures.
