Medical Disclaimer: All content on this website is compiled from public user discussions for informational purposes only. This is NOT medical advice. Peptides and GLP-1 agonists are prescription compounds. Do not start, adjust or stop any treatment without consulting a licensed healthcare provider. We do not endorse any peptide vendor or medical treatment.
What a COA Is Supposed to Be
A Certificate of Analysis is the document connecting a specific batch of product to specific analytical results. A proper COA has: a batch or lot number that matches what is physically printed on your vial; the test methods used; the results - at minimum analytical HPLC purity with an actual chromatogram, and mass spectrometry confirming the molecule’s identity; and the date and signature or identity of the testing entity.
The three questions a COA exists to answer are simple: is it the right molecule (mass spec), is it clean (HPLC purity), and does this paper actually belong to my vial (batch match). Every red flag below is a way of dodging one of those three questions.
Purity vs. Net Peptide Content - The Classic Confusion
This distinction is the most-abused concept in peptide sales. Purity is the fraction of peptide material that is your target compound, measured among peptide substances by HPLC. Net peptide content is the fraction of the vial’s total weight that is peptide at all - the rest is typically counter-ions, salts and residual water from lyophilization.
A vial can honestly claim “99% pure” while containing, say, 60–80% actual peptide by weight. Both numbers can be true simultaneously. Reputable certificates report both; marketing pages report only the bigger-sounding one. If a vendor quotes purity but cannot tell you net content, you do not know your dose - and in a dose-dependent drug class like GLP-1 agonists, not knowing your dose is the whole ballgame.
Red Flags on Vendor COAs
Learn these patterns and you can filter most of the market in minutes: no chromatogram - a purity number without the trace is a claim, not a measurement; no mass spec - without MS, identity is unverified and substitution is undetectable; no batch number, or batch numbers that never change - the same certificate “proving” every vial for years is recycled, not per-batch; template COAs - identical layout and results across different compounds and vendors, a signature of document laundering; impossible uniformity - real HPLC purity varies batch to batch (97.3%, 98.8%, 99.1%); a vendor reporting exactly “99%” on every batch is rounding fiction.
Also verify the testing entity. A COA from the vendor itself is weaker than one from an independent lab; the strongest signal in this market is a named third-party laboratory whose result you can confirm by contacting them. See our guide to third-party testing.
Putting It Into Practice
When evaluating any vendor - the one this site covers or any competitor - ask for the COA before purchase, check the batch logic, and compare against previous certificates the vendor has published. Consistent format with varying, plausible results and matching batch numbers is what real documentation looks like. For the broader vendor-evaluation framework, see Is Nexaph Legit, and for the compound science, What Is Retatrutide.
The Analytical Methods Behind a COA: A Comparison
A COA is only as meaningful as the methods it reports, so the method table comes first. These are the standard techniques, what each actually measures, and what it cannot tell you:
| Method | What it measures | Typical output | What it does NOT prove |
|---|---|---|---|
| Analytical HPLC (UV) | Chromatographic purity - what fraction of UV-absorbing material is the target peak | Main peak area %, impurity peak list | Identity of any peak; non-UV-absorbing contaminants like salts |
| Mass spectrometry (LC-MS / MALDI) | Molecular mass of the main species | Observed m/z vs calculated mass | Purity; a mass match can coexist with significant impurities |
| Amino acid analysis | Composition and net peptide content | Residue ratios; % peptide vs counter-ion/water | Sequence order |
| Endotoxin test (LAL) | Bacterial endotoxin load | EU per mg | Sterility |
| Quantitative NMR (where present) | Independent content and purity check | Weight % | Full impurity identification |
The HPLC/MS combination explains why credible COAs carry both: HPLC says “mostly one thing,” MS says “the thing has the right mass” - and the two together still say nothing about endotoxin, which is exactly why the LAL row exists and why its absence on a vial destined for injection is a meaningful gap. This division of labor is the core literacy skill: no single line on a COA is sufficient, and every line answers a different question.
Reading a Chromatogram: Worked Parameters
The chromatogram is the heart of the document, and four parameters carry the information:
| Chromatogram parameter | What to look for | Red flag |
|---|---|---|
| Main peak retention time | Consistent with the compound’s method and the claimed purity claim across batches | Retention time jumping between COAs of the same compound |
| Main peak area % | ≥98% is the research-grade convention; ≥99% claims should show equally clean traces | 99% claimed with visible shoulder peaks |
| Impurity peaks | Small, labeled, and consistent batch to batch | Unlabeled shoulders or truncation hiding the baseline |
| Batch linkage | The chromatogram header carries your vial’s batch number | “Representative” data; batch numbers that do not match |
A note on the arithmetic that COAs invite readers to skip: purity and net content are different numbers with different meanings. A vial labeled 10 mg at 99% HPLC purity may contain only ~8 mg of actual peptide once an 80% net content is accounted for - the counter-ion and residual water account for the rest. Vendors who quote purity prominently and net content obscurely are not lying, but they are choosing which truth to make easy. The full parameter-by-parameter breakdown of what a complete COA contains is on our peptides overview, and the testing ecosystem that produces these documents is covered in the third-party testing explainer.
Frequently Asked Questions
What purity should a peptide COA show?
Research-grade peptides typically spec at 95-99%+ purity by analytical HPLC. But the number matters less than the evidence: a chromatogram and mass-spec data behind it. "99%" with no trace attached is marketing.
What is the difference between purity and net peptide content?
Purity is the fraction of peptide material that is the target compound; net content is the fraction of total vial weight that is peptide at all (the rest is salts and water). A 99% pure vial can still be mostly non-peptide by weight. Both numbers are needed to know the dose.
Can COAs be faked?
Yes. Recycled certificates, template documents shared across vendors, edited PDFs and borrowed third-party lab results are all common. Cross-check batch numbers, look for batch-to-batch variation, and confirm third-party results directly with the lab where possible.
What is the single most important line on a COA?
The batch number linkage - a COA that does not match the batch printed on your vial is not evidence about your vial at all, whatever its purity claim. After that, the HPLC chromatogram and MS mass confirmation together form the core.
Can a COA be faked?
Yes - screenshots circulate stripped of provenance, and template documents get reused across “batches.” The only structural defense is a named third-party lab that can confirm the report when contacted; vendor-side documents are inherently medium-tier evidence.
What does “99% purity” miss?
Purity by HPLC does not cover net peptide content (counter-ion and water), endotoxin load, or sterility - all separate parameters with separate tests. A high purity number alone is not a safety or dosing guarantee.
Important Safety Disclaimer
Disclaimer: All content on this website is compiled from public user discussions for informational purposes only. This is NOT medical advice. Peptides and GLP-1 agonists are prescription compounds. Do not start, adjust or stop any treatment without consulting a licensed healthcare provider. We do not endorse any peptide vendor or medical treatment.