While running blood samples you may need to make sure the Cogent Diamond Hydride™ HPLC column is clean from run to run. 

What can I do in terms of solvent washings to remove strongly retained materials from the column?

Answer: The first thing you can do is have a solvent wash step in your injection sequence. For example, every 10 injections or so you might have a solvent wash method to elute strongly adsorbed materials from the column. A good wash solvent to use for this purpose is 50:50 DI water / methanol or 50:50 DI water / isopropanol. After the wash step, the sample injections can resume. 

Another approach is to incorporate the wash directly into the sample injection method itself. Your method could have solvent A as 50:50 DI water / methanol or 50:50 DI water / isopropanol. At the end of the gradient, you could go to 100%A and hold, to elute materials from the column. In this manner, you can clean the column continuously in every run. 

If you already have a method with a 100% aqueous A solvent, try substituting with 50% IPA or methanol and see how it works. The chromatography should not be drastically affected other than perhaps a slight shift in retention time.

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