chromolith

[lotussss]

Hello,
My question is about a separation of steroids with the chromolith column . I have a very complex mixture to separate. Two steroids are very retained (2 times more retained than principal peak). Only column which separates them is a chromolith RP18e (no other C18 , gradient, temperature, THF, salt, effects of pH). My question is: Is it possible that the chromolith is compared with the chromatography of exclusion of size in this case? Can Mesoporous (size: 2nm) or megaporous (2µm) do that?
Thank you

[tom jupille]

First of all, I think you're off by a bit on the mesopores. Merck's web site says 13 nm (130 Ã… for us old-timers). That's roughly the same as most C18 packings.

The macropores, at 2 μm, are too big to show any size exclusion effects with something as small as a steriod. To put this in perspective, protein SEC is typically done with pore sizes in the range of 20 - 40 nm (200 - 400 Ã…).