Peptide retention, recovery- TFA/HFBA vs ClO4-

[DJ]

It has been stated that an additive that increases retention of a peptide/protein on a RP support, (C4 column) should also decrease recovery. An example of this would be use of TFA vs HFBA as ion pairing agents on an otherwise identical system (recovery of peptide better with TFA over HFBA).

Is it the case that anything that increases retention should also decrease recovery?

For instance, a series of papers emerged a few years ago using NaClO4 (30 mM) as ion pairing agent along with H3PO4 or TFA. The authors report that use of perchlorate with H3PO4 or TFA resulted in greater retention than when TFA or H3PO4 used alone. Since ClO4- is an additive that increases retention (relative to TFA), would you still expect poorer recovery in the perchlorate system as you would if it were an HFBA system?

[tom jupille]

It has been stated that an additive that increases retention of a peptide/protein on a RP support, (C4 column) should also decrease recovery.

Stated when, where, and by whom?

I can see a "common sense" argument (the more time the analyte spends in the stationary phase, the more likely it is to get stuck there), but I would *not* want to make a general statement to that effect without some hard evidence.