After synthesis, crude peptide mixtures contain the desired product along with various impurities including truncated sequences, deletion peptides, and side-reaction products. Purification is essential to isolate the target peptide at the required purity level.
Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) is the gold standard for peptide purification. It separates molecules based on their hydrophobic interactions with a C18 stationary phase, using a gradient of increasing organic solvent (typically acetonitrile) in water with a small percentage of trifluoroacetic acid.
For larger-scale purifications or peptides with specific requirements, additional techniques such as ion-exchange chromatography, size-exclusion chromatography, or affinity chromatography may be employed either alone or in combination with RP-HPLC.
The purified peptide is then lyophilized (freeze-dried) to produce a stable powder, analyzed for purity and identity, and packaged under controlled conditions to ensure consistent quality from batch to batch.