In chemical terms, a counterion is an ion that has the opposite charge to another ion in a solution or electrochemical system. In peptide synthesis, counterions such as TFA are used to separate peptides from resins and for high-performance liquid chromatography. Specifically, when the sequence contains basic amino acids, such as Arg, His, and Lys, or contains N-terminal free amino groups, TFA is required for protonation, thereby obtaining TFA salts. However, in cell experiments, high concentrations of TFA may have certain effects. Keshengjing peptide provides two high-quality TFA removal services: guaranteed TFA removal (guaranteed TFA content <1%) and standard TFA removal (TFA<10%).