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A Certificate of Analysis is the single document that tells you what is actually in a vial. This guide walks through every field, what an accredited lab must provide, and the red flags of a faked certificate.
A serious Certificate of Analysis reports the following. If a field is missing, treat the gap as information.
| Field | What it should show |
|---|---|
| Product / Sequence | Full name and, ideally, amino-acid sequence — matching what was ordered. |
| Batch (Lot) No. | A unique lot number that matches the label on the vial. |
| Mfg / Retest date | Manufacture date and a retest/expiry; analysis date contemporary with manufacture. |
| Appearance | Physical description of the material (e.g. white lyophilized powder). |
| Purity by HPLC | ≥98% target, with the chromatogram attached showing the main peak and area %. |
| Identity by LC-MS | Found mass ([M+H]+) matching the expected monoisotopic mass. |
| Water (Karl Fischer) | Residual water content — lowers the true net peptide mass. |
| Endotoxin (LAL) | Bacterial endotoxin in EU/mg or EU/mL, for cell-culture or in-vivo research. |
| Storage | Conditions under which the certified values hold (e.g. −20 °C, protect from light). |
A seller cannot objectively certify its own product. Look for an independent lab, ideally ISO/IEC 17025 accredited. An accredited lab should provide:
HPLC quantifies purity as a percentage. LC-MS confirms the molecule's identity by mass. You need both: HPLC alone can report 98% of the wrong molecule, and MS alone does not quantify purity. A complete analytical section shows the chromatogram, the purity value, and the mass spectrum with the expected [M+H]+.
Two fields are often quietly omitted and materially change the picture: Karl Fischer water content and endotoxin (LAL). Residual solvents and counter-ion content (e.g. TFA/acetate) may also be relevant. Their absence means the composition and safety picture is incomplete.