# Manufacturer COA vs Third-Party COA: What Actually Differs
Every peptide vial ships with a Certificate of Analysis (COA). Most buyers assume a COA is a COA. It is not. A manufacturer-issued COA and an independent third-party COA are built for different audiences and disclose very different things.
What a manufacturer COA typically shows
A manufacturer COA is a release document. Its job is to certify that a specific lot passed the supplier's internal quality gate before it left the facility. Common fields:
- Peptide name and lot number
- Reported purity percentage (usually HPLC area %)
- Molecular weight (sometimes theoretical, sometimes measured)
- Appearance, solubility, and net peptide content
- A single chromatogram thumbnail (often unlabelled)
What manufacturer COAs frequently omit: the analytical method version, the column and mobile phase used, integration parameters, related substances (impurity peaks named and quantified individually), heavy metals data, residual solvents, endotoxin values in EU/mg, water content by Karl Fischer, and the identity of the analyst or lab that ran the test.
What a third-party COA is supposed to add
An independent lab has no commercial interest in the lot passing. Its COA is an audit document. A useful third-party COA includes:
- Full method disclosure (column, gradient, wavelength, injection volume, temperature)
- Named impurity peaks with retention times and area %
- Orthogonal identity confirmation (LC-MS with observed vs theoretical mass, delta ppm)
- Heavy metals by ICP-MS with individual element limits
- Residual solvents by GC-MS against ICH Q3C class limits
- Endotoxins by LAL (kinetic chromogenic) in EU/mg
- Water content by Karl Fischer titration
- Analyst signature, accreditation reference, and report date
The chromatogram is full-page, annotated, and reproducible.
