What are capillary columns?

In CE, a capillary column is a thin, hollow tube with a narrow diameter that is typically coated on its inner surface with a liquid phase or adsorbent. Capillary columns in CE are usually made of fused silica and have an inner diameter of 50 μm and a length of 25 cm. Fused silica is used due to its high purity and low surface activity. To enhance durability, the outer surface of the tube is typically coated with polyimide resin.