Where it comes from
Trifluoroacetic acid is used as an ion-pairing agent in reverse-phase purification. Basic residues retain trifluoroacetate as a counter-ion through lyophilisation.
The mass implication
Counter-ion content contributes to net weight without contributing peptide. This is precisely the gap between net weight and peptide content, and it is larger for sequences rich in basic residues.
When it matters
For cell-based work, residual TFA can be relevant to the experiment itself, not just the maths. Where a salt-exchange is required, ask before ordering — we will tell you the counter-ion form of the current batch.
Research use only
All materials referenced here are supplied by Aura Peptide Co. strictly for in-vitro laboratory and research use. Nothing on this page is guidance for human or animal use.