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Certificates of Analysis: What a COA Is and Is Not
A COA reports test results for one specific lot. What a credible certificate contains, which tests matter for peptides, and the limits of what any COA can tell you.
Bench card
- A COA applies to one lot. A certificate without a matching lot number tells you nothing about your vial.
- For peptides, the core tests are identity by mass spectrometry and purity by HPLC.
- A credible COA names its methods, shows the data, and is signed and dated by a responsible person.
- Third-party testing adds independence; ask how the sample was selected.
- A COA describes material at the time of testing, not after shipping and storage.
A certificate of analysis (COA) is a document that reports the results of tests performed on a specific batch, or lot, of material. In regulated manufacturing it is part of a controlled release system. In the research peptide market its quality varies widely, so it pays to know what to look for.
One lot, one certificate
Each manufacturing run produces a lot, and each lot can differ in purity, content and impurities. A COA is only meaningful for the lot it names. ICH Q7, the GMP guide for active pharmaceutical ingredients, expects certificates to identify the material, its lot number and the date of release, and to list each test with its acceptance limits and results.
Tests you should expect for a peptide
| Test | Answers | Typical method |
|---|---|---|
| Identity | Is it the right molecule? | Mass spectrometry (ESI or MALDI) |
| Purity | How much of the peptide material is the target sequence? | Reversed-phase HPLC with UV detection |
| Appearance | Does it look as expected? | Visual |
| Peptide content | How much of the powder is peptide? | Amino acid analysis or nitrogen analysis |
| Water | How much moisture? | Karl Fischer titration |
| Counterion | How much TFA or acetate? | Ion chromatography or other methods |
| Endotoxin, sterility | Biological contaminants | Only for specific applications |
Most research COAs report identity and purity only. That is enough to confirm the right molecule at a stated purity, but not to calculate an exact peptide concentration.
Signs of a credible COA
- Lot number that matches the vial.
- Date of analysis.
- Methods named, with key conditions (column, wavelength, ionization mode).
- Raw data attached: a chromatogram with integrated peaks and a mass spectrum.
- The testing laboratory named, and whether it is the supplier’s own or an independent lab.
- A signature or approval from a responsible person.
Warning signs
- No lot number, or the same certificate reused across lots.
- Round-number purity with no chromatogram.
- Expected mass stated, but no observed mass or spectrum.
- Images that look edited, or a chromatogram with no axes or scale.
- A testing lab that cannot be identified or contacted.
For a walk-through of reading the numbers on a real certificate, see Interpreting a COA.
CL-05
Reviewing a certificate of analysis
What to check before material is accepted into inventory.
References
- ICH Q7. Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients (including section 11.4, Certificates of Analysis). International Council for Harmonisation, 2000. ICH
- US FDA. Current Good Manufacturing Practice for Finished Pharmaceuticals, 21 CFR Part 211. eCFR
- ISO/IEC 17025:2017. General requirements for the competence of testing and calibration laboratories. ISO
- US FDA. ANDAs for Certain Highly Purified Synthetic Peptide Drug Products That Refer to Listed Drugs of rDNA Origin. Guidance for Industry; 2021. FDA
- D'Hondt M, Bracke N, Taevernier L, Gevaert B, Verbeke F, Wynendaele E, De Spiegeleer B. Related impurities in peptide medicines. J Pharm Biomed Anal. 2014;101:2–30. DOI