Proposed Mechanism for TFA Signal Suppression and the "TFA-Fix"

TFA can be displaced from the ion-pair complex by exposing the effluent to a higher concentration of a different acid post column and before the MS detector. This is referred to as the "TFA-Fix".That is to say: Signal Suppression due to Additives (ESI signal suppression by TFA)
Ion pairing with analyte --> surface tension effect

Solutions:
Post-column addition of a sheath liquid of propanoic acid (10%) in 2-propanol (TFA Fix)
Use low concentrations of TFA with acetic acid (TFA Light)
Replace TFA

Always remember: Achievement of gaseous analyte ionization at API interface is the key to MS detection.

Reference: Agilent LC/MS Method Development Resource.