Peptide identity vs purity: two questions every lab should separate

For synthetic research peptides, “is this the right molecule?” and “how clean is this sample?” are related but not identical questions.

Identity (often mass spectrometry / LC-MS) asks whether the observed mass and fragmentation pattern are consistent with the intended sequence. Purity (often HPLC) asks what fraction of the UV-detectable material sits under the main peak under a stated method.

Why the split matters in peptide research documentation:

• A high HPLC area % does not by itself prove sequence identity. • An identity-consistent mass does not by itself describe impurity profile. • Your experiment’s acceptance criteria should name both — and should cite the lot COA method, not a marketing purity slogan.

On this blog, keep the conversation about analytical interpretation and literature methods. Do not turn purity percentages into personal-use claims.