typical salt concentration in sample for SEC

[alicee!]

hi.. i have a basic question..
i wish to know the typically used salt concentration in the sample that is to be injected on the TOSOH SEC silica based column... should my sample be in higher salt say 100 mM salt or in lower salt.. 10 mM salt.. and why?

thanks

[Uwe Neue]

The best approach is to inject the sample with the same salt concentration and buffer pH as the mobile phase. The reason is that these mobile phase conditions have been set up to be favorable for SEC, avoiding silanol interactions and similar secondary interactions. If you inject the sample in something else, there is a high chance that you will create additional interactions, and that this will influence the retention (or better: the desired lack of retention).