Equilibration – As much as necessary, as little as possible

During equilibration and rinsing a column, the following question often arises: “For how long do I have to flush the column?” If the (re)equilibration time is too short, there is a risk of non-reproducible results (e.g. retention time shift). If in doubt a longer duration of flushing should be favoured. But if the rinse time is too long, time and, especially for preparative methods, solvents are wasted.

Practical example
A YMC-Triart C8 column (TO12S03-1546WT, column volume 2.5 mL) was rinsed with 50 mL of acetonitrile before each run. A plant extract was injected under four different conditions:

• without equilibration
• equilibration with 1 column volume
• equilibration with 5 column volumes
• equilibration with 10 column volumes

Result
It is obvious, without sufficient equilibration the retention time shifts to shorter times. When using 5 or 10 column volumes, the results of this application are reproducible. Equilibration with 5 column volumes is most efficient.

For detailed and further information, e. g. on how to calculate the column volume, download the technical document here.