All liners gradually become dirty and the surface becomes active, making them unsuitable for most samples. Cleaning a liner will never return the liner to its original level of deactivation, and in many cases, it is cheaper to replace the liner to ensure high quality and consistent deactivations.
To clean a liner with no visible deposits or discoloration, it is best to rinse the inside with the following solvents in sequence:
- methanol,
- then methylene chloride, and
- then hexane.
Use a cotton swab or pipe cleaner to gently scrub the inner surface of the liner, but be very careful not to scratch the liner and thereby remove the deactivation layer. If deposits are visible or the liner is discolored, it may be necessary to ultrasonicate the liner in methanol, then methylene chloride, and then hexane. Some deposits must be removed by heating the liner to 450–500 °C for one hour. These temperatures will remove some deactivation layers but will not harm a Siltek coating. Higher temperatures can soften the liner itself. Heat treating a liner to remove stubborn organic matter will remove the deactivation, not remove all of the organic matter or other non-chromatographable material, and will require redeactivation. Redeactivation processes available to chemists in the lab require time and reagents, are somewhat dangerous, and produce toxic waste materials. Furthermore, the quality of the redeactivation is never as good as the original liner deactivations. When all costs are considered, replacement often is less expensive.
