Capillary Columns

The capillary column is widely used mostly in gas chromatography. But it is not limited to the capillary columns. The capillary column consists of long tube that can be made of metal, glass or quartz. The typical capillary columns are usually made of quartz. The diameter of the capillary columns ranges from 50 to 500 um, and the length usually from 5m to 200m.

The stationary phase in the capillary columns is coated as a thin film (ca 0.25um thick) on the internal surface of the tube and, during manufacture the outside of glass or quartz tubes are coated with a polyimide resin to provide mechanical strength and prevent atmospheric erosion. The external coating in the capillary columns can remain stable up to about 250 degree C. The stationary phase of the capillary columns is usually coated on the inside of the column using one of several, special, coating procedures. The most important features of the capillary column are its small flow impedance relative to that of the packed column. This permits very long columns to be used and thus, provide very high efficiencies or, alternatively, very short columns operated at very high mobile phase velocities to provide very fast separations.