How to Interpret a Certificate of Analysis (COA)
EXOMA Scientific Team · Publicado el · Actualizado el
Complete guide to understanding the HPLC, mass spectrometry and purity results that appear in peptide certificates of analysis.
How to Interpret a Certificate of Analysis (COA) of a Peptide
Un Certificate of Analysis (COA) certifies the identity, purity and quality of a specific batch. In reproducible research it is the most important document after the compound itself.
Anatomy of a properly issued COA
1. Lot identification
- Exact chemical name + synonyms.
- Lot # traceable.
- Manufacturing and expiration date.
- Expected appearance (typically "white to yellowish-white lyophilized powder").
2. Chemical identity
- Sequence (one- and three-letter).
- Molecular formula.
- Theoretical molecular weight vs measured by MS.
- CAS number when applicable.
3. Purity by HPLC
| Parámetro | Estándar EXOMA |
|---|---|
| Sistema | RP-HPLC C18 |
| Detección | UV 220 nm |
| Pureza mínima | ≥ 99% |
| Impurezas individuales | < 0.5% c/u |
The chromatogram should show a clean, symmetrical main peak.
4. Mass spectrometry
- MALDI-TOF o ESI-MS.
- Measured mass must match the theoretical (±1 Da small peptides, ±2-3 Da large ones).
5. Additional analysis
- Net peptide content (corrects for counterion, water, salts). Critical: a "10 mg" vial may contain 7-8 mg of real peptide plus TFA and water.
- Acetate / TFA content.
- Amino acid analysis (AAA).
6. Biological safety
- Endotoxins (LAL): <0.25 EU/mg.
- Sterility when applicable.
- Bioburden.
7. Signature and traceability
- Responsible analytical laboratory, chemist's signature, QR code.
Red flags
- Purity <99% declared as "high purity".
- Ausencia de cromatograma.
- No mass measured by MS.
- Sin endotoxinas LAL.
- No specific batch.
- No net peptide content.
How EXOMA verifies each lot
- HPLC per batch with chromatogram.
- Identity MS.
- LAL for endotoxins.
- Digital COA with unique lot code, viewable online without download.
- QR traceability from shipment to the analytical lot.
Example of HPLC chromatogram
| Pico | Tiempo | Área (%) | Interpretación |
|---|---|---|---|
| Principal | ~12.4 min | 99.4 | Péptido objetivo |
| Menor | ~10.8 min | 0.3 | Impureza des-amido |
| Menor | ~13.1 min | 0.3 | Truncamiento N-terminal |
Why it matters
- Reproducibility: two batches with different purities give different results.
- Statistical validity: contaminants bias pharmacological effects.
- Comparability across studies.
- Safety in animal models (endotoxins are potent inflammatory confounders).
References
- USP <1503> Quality Attributes of Peptide Products.
- ICH Q6A — Specifications for Drug Substances.
Technical reference material for scientific research.