Short answer: A Certificate of Analysis (COA) is a laboratory report describing what one specific batch of a compound was measured to contain. Read it in five steps — confirm the compound identity, check the purity figure and the method behind it, match the batch number to the product in your hand, check the test date, and confirm the issuing laboratory can be verified independently.
This article is educational. It explains how analytical documentation works and how to read it. It does not provide usage, dosing or administration guidance of any kind.
What a Certificate of Analysis is
A Certificate of Analysis is a report issued by an analytical laboratory that documents the results of testing a sample drawn from a particular production batch. For peptides and other research compounds, a COA records two core findings — the identity of the molecule and its measured purity — together with the metadata that ties the report to a specific batch.
The important word is batch. A COA is not a statement about a product line, a brand, or a supplier. It is a statement about one production run, tested on one date. This distinction does most of the work when you are judging whether a certificate means anything.
The five things to check, in order
| # | What to check | Why it matters |
|---|---|---|
| 1 | Compound identity and expected molecular mass | Confirms the sample tested is the molecule named on the label, not something else |
| 2 | Purity percentage and the method used | A percentage with no stated method is not a result, it is a claim |
| 3 | Batch number | Must match the batch printed on the product you actually received |
| 4 | Test date | A certificate from an older production run says nothing about the pack in your hand |
| 5 | Issuing laboratory | Named, contactable, and able to confirm the report independently of the seller |
What does HPLC purity actually mean?
HPLC stands for High-Performance Liquid Chromatography, and it is the method most commonly used to separate and quantify the components of a synthetic peptide sample (Streuli et al., 2026). The sample passes through a column that separates its components according to their chemical properties. A detector records each component as a peak on a chromatogram. The area of the main peak, expressed as a proportion of the total area of all peaks, gives the reported purity figure.
So a purity of 98.4% does not mean the remaining 1.6% is harmless, or identified, or even characterised. It means that under those chromatographic conditions, the dominant peak accounted for 98.4% of the total detected peak area. A serious COA includes the chromatogram itself, not just the number derived from it.
How is identity confirmed?
Mass spectrometry measures the molecular mass of the compound. Every peptide has a molecular mass determined by its amino acid sequence, so a measured mass matching the expected mass confirms identity. Published work on reference standards for synthetic peptide therapeutics describes the use of LC-MS/MS to confirm both molecular mass and amino acid sequence, and notes that identity and purity are properly established using orthogonal techniques — several independent methods that corroborate one another (McCarthy et al., 2023).
A COA that reports a purity figure but never confirms identity has answered the less important question. Purity tells you how much of the dominant substance is present. Identity tells you whether the dominant substance is the one named on the label.
How to tell a credible COA from a fabricated one
A credible certificate is coherent, traceable and independently checkable. Practical signals:
- Batch and date align. The batch number on the certificate matches the batch on the physical product, and the test date is recent and plausible for that run.
- Methods are stated. The document names the techniques used — HPLC for purity, mass spectrometry for identity — rather than presenting a bare percentage.
- Raw data is attached. The chromatogram and mass spectrum are included, not just the summary figures derived from them.
- The laboratory is identifiable. Name, contact details, and ideally a report identifier that allows the result to be confirmed at source.
- No marketing language. An authentic COA reports analytical data. It does not make health claims or promotional statements.
Warning signs run the other way: no batch number, no chromatogram, suspiciously round figures with no supporting graphs, a copied laboratory logo, or a laboratory that cannot be contacted to confirm the report.
"Lab tested" is not the same as "third-party tested"
| Phrase | What it can mean | What to ask |
|---|---|---|
| Lab tested | Anything, including testing by the manufacturer on itself | Which laboratory, and who paid for the result? |
| Third-party tested | Tested by a laboratory with no commercial stake in the outcome | Can the laboratory confirm the report directly? |
| Batch tested | Each production run is tested, not one representative sample once | Does the certificate match my batch number? |
These three phrases are often used interchangeably in marketing. They are not interchangeable. A supplier can honestly say "lab tested" having tested one batch, once, years ago, in its own facility.
What a COA does not tell you
A certificate confirms what was in the tested sample. It says nothing about whether a substance is safe, whether it is legal to supply or possess in your jurisdiction, or whether it has been evaluated by any regulator. Those are separate questions, and a purity figure — however high — does not answer any of them.
Related reading
For the analytical documentation associated with individual compounds, see our lab testing page. For background on compound classes, see What Are SARMs? The 2026 Research Guide and Do Oral Peptides Actually Work?
References
- McCarthy D., Han Y., Carrick K., Schmidt D., Workman W., Matejtschuk P., Duru C., Atouf F. Reference Standards to Support Quality of Synthetic Peptide Therapeutics. Pharmaceutical Research, 2023, 40:1317–1328. DOI: 10.1007/s11095-023-03493-1
- Streuli A., Erckes V., Nardone B., Bedard V., Beland F., Steuer C. Improvement of Analysis and Transferability in Peptide Purification: From HPLC to FPLC and Back Again. Journal of Peptide Science, 2026, 32(3):e70090. DOI: 10.1002/psc.70090
Research use statement: This article is provided for educational and informational purposes only. Research compounds referenced here are intended solely for laboratory and educational use and are not for human consumption. They are not authorised medicines and have not been evaluated by the MHRA, EMA or FDA. Nothing here constitutes medical advice, diagnosis or treatment, and nothing here encourages use, dosing or administration.