Depending on the analytes you use the column with, there are a number of strategies you can try:
• If your HPLC system can have more than two solvents, you could include a third line with your cleaning solvent. Then in the injection sequence you could insert a wash step which uses only the third solvent. The nature of the samples will dictate how frequently you need to do a washing. For serum samples, we recommend about every ten injections or fewer.
• Using a guard column can be an effective technique because strongly adsorbed contaminants will build up at the front of the column. Therefore if you have a guard column attached, these compounds will build up here instead of on the analytical column. You can then replace these guard cartridges as needed.
• You can also backflush the analytical column. If the column is facing the other direction, the contaminants will come off more easily.
The advantage of using Cogent™ columns over those based on ordinary type B silica is that they can be more readily cleaned and restored to initial conditions. The reason is because of surface differences between the two materials. Cogent™ columns are based on TYPE-C Silica™, which is more hydrophobic and has virtually no silanols. Contaminants can therefore be more readily washed from the column. In contrast, contaminants may be more strongly adsorbed onto type B columns due to the more active surface sites on this material.