Quality control 09
Purity Is Not Potency
Purity asks what a method detects in the vial; potency asks whether the material performs the intended function in a suitable assay.
A peptide can be highly pure and biologically inactive. Purity and potency are different properties, and confusing them is expensive because a purity trace can look excellent while a functional assay reads zero.
Purity describes the detected composition under an analytical method. Potency depends on whether the molecule has the correct sequence, folding, chemical state, and — for many peptides — disulfide connectivity required for its function.
Failure modes that can preserve a clean-looking trace
A chromatographic purity result cannot substitute for a validated functional assay. Process discipline, handling, complementary structural evidence, and supplier history all help reduce the risk, but a potency claim requires a method designed to measure function.
- Wrong folding or disulfide connectivity: the same atoms and mass can form the wrong three-dimensional structure.
- Deamidation of asparagine or glutamine, which can alter binding or function.
- Oxidation, especially at methionine, which can reduce or abolish activity.
- Correct-mass but inactive species, including diastereomers created by racemization during synthesis.
Sources and evidence record
Research-use quality education only. This material does not establish suitability for human or veterinary use and is not dosing guidance.