Guard Column or Retention Gap?

Retention gaps are mainly used for focusing sample components when introducing a large (liquid) sample directly onto the column, whereas, guard columns are used to protect the analytical column from contamination. When using a retention gap system, the retention gap will also act as a guard column, but its primary function is to create a focusing effect. This article will look at how retention gaps are used with different modes of injection and how to cost effectively use guard columns.