Peptide Content vs Purity
Suppliers may report both net peptide content and chromatographic purity on a COA. These values answer different questions and should not be used interchangeably in specifications or payment release criteria.
Key definitions
- Peptide content (net peptide content)
- The amount of active peptide relative to total mass, often accounting for counter-ions, water, or salts. May be expressed as mg per vial or percent by weight.
- Purity (HPLC area percent)
- The proportion of the main chromatographic peak versus other detected peaks under a stated method. Reflects related substances, not necessarily total mass balance.
Why the numbers differ
- A vial labeled 5 mg may contain less than 5 mg net peptide if content is not adjusted for salt form.
- A 98% HPLC purity result does not automatically mean 98% peptide content by weight.
- High purity with low net content can still under-deliver active material for assay work.
- Buyers should request both values when specifications matter to their program.
What buyers can document
- State both content and purity requirements in purchase specifications when either matters to your assay.
- Ask how net content is calculated, including salt form and moisture assumptions.
- Request the HPLC method summary used for purity integration.
- Weigh or assay incoming material when specifications are critical — COA review alone may be insufficient.
For laboratory research and analytical use only. Not for human consumption. Not intended to diagnose, treat, cure, or prevent any disease.