Is it possible for non-retained compounds to elute before V0

[Mike H.]

Can analytes be so polar that the elute before the void time? I'm asking because I tested some material a while back where it looks like this happened.

[tom jupille]

Depends on exactly how you define the void volume of the column. If you take it to be the total volume of liquid, both between the particles and inside *all* of the pores, then it is quite likely that some compounds will elute before t0 due to exclusion from the pores. This can be either size exclusion (too big to get in) or ion exclusion (same charge on the analyte and the stationary phase surface).

If you go back and look at the archives (the "old" version of the Forum from 1999 - 2004), you'll find quite a discussion on how to best get an accurate measurement of t0. If I recall, D2O was suggested as a likely candidate to totally permeate all the pores (and be detected by RI).

[Mike H.]

Appreciate the detailed respone.