HPLC column structure and connection

hplc column yazawa shool structure

A typical HPLC column has a structure as shown in the figure above.

At both ends of the column pipe, which is filled with the packing materials responsible for compound separation, there are porous disks called 'frits'. These are held in place by end-fittings.

The role of the 'frit' is to prevent the packing materials from escaping the column pipe, not to act as a 'filter' as commonly mentioned.

The 'end-fitting' serves two roles. One is to press the frit against the column pipe to prevent the packing materials from spilling out, and the other is to connect the tubing to allow the mobile phase and solutes to pass through the column without leaking.

HPLC tubing is typically made of PEEK or stainless steel, with an outer diameter of 1/16 inch and an inner diameter of 0.1-0.3mm. To connect HPLC tubing to the column, a male nut is required. In addition, at the tip, there is a cone-shaped structure called a 'ferrule' which firmly grips the tubing to prevent leakage under high pressure.

For the solutes flowing inside the tubing to be accurately and fully injected into the column, the tip of the tubing needs to make firm contact with the bottom surface of the column's end-fitting. Therefore, when tightening the male nut, the tubing's tip must protrude 2-3mm from the ferrule. If the tubing is not tightly adhered to the bottom surface of the end-fitting, the solutes may linger there, causing peak tailing or, in the worst-case scenario, mobile phase leakage. The tip of the tubing must also be flat.
Maintenance of the tubing connecting the column is also an important task in HPLC.

WG11 / YAZAWA Itaru,