The net peptide content (NPC) is the fraction of peptidic material (i.e. the requested peptide and the peptidic impurities) relative to counter-ions and residual water. The latter do not contain nitrogen, allowing the determination of the net peptide content by elemental analysis. Additionally, the NPC can be determined by amino acid analysis. For more guidance on net peptide content and peptide properties, take a read of our peptide guide for beginners.