►HPLC. After being cleaved off the solid support, the crude synthetic peptide is analyzed by reverse phase HPLC to determine its purity. At this stage, a medium-size peptide (e.g., a 20-mer) typically contains ~80% of the desired sequence, the rest consisting of truncation, deletion and other byproducts. While this purity may be judged acceptable for some purposes, e.g., antibody production, for most biomedical applications it is advisable to work with purer (>90% by HPLC) materials. Larger, e.g., 40-50 residue peptides, tend to give complex, heterogeneous crudes where the target sequence may only be represented at ~50% level, hence making purification mandatory.

Purification is usually done by semi-preparative HPLC, using similar stationary and mobile phases than in the analytical separations. Typically, a single HPLC step will furnish peptide material of 90-95% purity, acceptable for most purposes. Higher purities (~98-99%) will usually require an extra HPLC step.


►Mass spectrometry. In order to detect the target peptide in the synthetic crude and to monitor the subsequent purification steps, MS analysis (LC-MS, MALDI-TOF) is used to ascertain that the measured mass is consistent with the expected composition.


►Other equipment. Additional instrumentation at the facility includes a freeze-drying unit, a multi-channel reader for peptide quantitation, ELISA and other applications, etc. Amino acid analysis for precise quantitation of peptides is also available on an outsourcing basis.