Laboratory quality
Potency
How much active peptide the vial actually contains, why the label mass is a starting point rather than an answer, and why potency is harder to measure than identity or purity.
- Last updated:
- 2026-07-22
Overview
Potency, for a peptide vial, is the amount of active molecule actually present. It is closely related to identity and purity but is distinct from both. A vial can be the right molecule (identity confirmed), be highly pure (99%+ by HPLC), and still contain less peptide than the label states because of water content, counter-ion mass, or loss during manufacturing.
Rigorous potency assays include amino-acid analysis, quantitative NMR, or bioassays against reference material. These are less common on routine research-supply CoAs than HPLC or LC-MS.
Why it matters
The Preparation Calculator on every compound page treats the label mass as the numerator when computing concentration. If the actual mass is lower than the label states, every downstream volume and syringe reading is proportionally wrong, and there is no way to detect this from arithmetic alone.
Key concepts
Peptide content vs. gross mass
The mass on the label may be gross weight (peptide plus counter-ion plus residual water) or net peptide content. Well-drafted CoAs distinguish the two.
Bioassay potency
For therapeutic peptides in the pharmaceutical world, potency is often measured in a biological assay (activity per unit mass). This is rare in the research-supply chain and requires reference standards that are usually not available.
Water content
Lyophilized material contains residual water. Water content is measured by Karl Fischer titration and can shift the effective peptide mass by several percent.
Common misconceptions
- "99% purity" does not imply the vial mass is 99% peptide. Purity is a percentage of the peptide-related material captured on HPLC; the vial's total mass includes counter-ion, water, and bulking agent.
- "Correct identity" does not imply "correct amount." The two questions are answered by different tests.
- A gravimetric weight measurement on a vial is not a potency assay by itself.
Practical interpretation
Where a CoA reports peptide content specifically (typically as "peptide content by AAA" or similar), that number, not the gross vial weight, is the closest available proxy for the mass the calculator should use. In research-supply practice this level of detail is uncommon.
Limitations
Healthy Mango does not run potency assays and cannot audit them.