- C18 columns
- Column comparison
New C18 columns tend to have more C18 ligand than do older, used C18 columns.
There are many possible reasons why a new C18 column (compared with an old C18 column of the same part number) exhibits longer retention.
A common cause is that old, used columns have lost C18 ligand as a result of hydrolysis.
As a column loses ligand, the surface becomes less and less hydrophobic. Installation of a new C18 column of the same part number may show significantly longer retention in some cases (especially if the used column is several years old).