The peptidic impurities and the net peptide content (NPC) have to be taken into account, e.g. for calculating the amount of solvent required for preparing a solution of a given concentration. The proportion of peptidic contaminants can be determined by analytical HPLC. The HPLC-purity corresponds to the fraction of the desired sequence, the lowest value mentioned on the ADS should be used for calculating the molar content:

Molar amount of desired peptide =

Gross weight x NPC (%) x HPLC-purity (%) / Mol. weight x 10’000

An example: Bradykinin acetate salt, gross weight 5 mg

HPLC-purity 98.7%, NPC (“Assay”) 85.0%, Mol. weight 1060.22 g/mol → net 4.195 mg (3.956 µmol)

This value allows calculating concentrations, when dissolving the peptide.