Reader’s guide · First edition · September 2026 · Revised September 15, 2026
Reading a Certificate of Analysis
What a real one contains, line by line, and the six ways a bad one gives itself away
Every guide the Society publishes ends with the same advice: ask for the certificate of analysis. This one explains what you are looking at when it arrives. A certificate is a lab's report on one batch of one product. Read properly, it tells you whether the vial contains what the label says, how much, and whether it is fit to inject. Read casually, it is a page of reassuring numbers, which is what most sellers count on.
Who this is for
Written for adults who have been handed a certificate of analysis for a peptide, compounded or otherwise, and want to know whether it means anything. It covers what the standard tests measure and what a complete certificate includes. It is not a substitute for a licensed pharmacy or an FDA-approved product, which come with these assurances built in.
A certificate of analysis (CoA) is a laboratory's report on tests run on a specific lot of a product. For an approved drug, the manufacturer generates one for every batch and the FDA can audit it. For a compounded preparation, the pharmacy either tests the batch or relies on its ingredient supplier's certificate plus its own process controls. For a research chemical, the seller may post a certificate, may post someone else's, or may post nothing.
- It is
- A snapshot of one sample from one lot, on one date, by one lab
- It is not
- A guarantee about a different lot, a different vial, or the same vial after months on a shelf
- Who runs them
- Manufacturers, pharmacies, and independent contract labs. The independence of the lab is the first thing to check.
- What it cannot show
- Whether the product works, whether it is safe for you, or whether it is legal to sell
The certificate is not the product
A seller who tests one vial from a batch and ships you another has told you about the one they tested. Ask whether the sample went to the lab from the sealed batch, whether the lab reports the lot number, and whether that number is on your vial.
| Test | The question it answers | What good looks like |
|---|---|---|
| Identity (mass spectrometry) | Is this molecule the one on the label? | Observed mass matches the expected mass of the peptide within a fraction of a dalton, with the method named |
| Purity (HPLC) | Of the peptide material present, how much is the intact peptide rather than fragments and by-products? | Percentage by chromatogram area, with the chromatogram shown, typically above 95% for research grade and above 98% for pharmaceutical |
| Quantity (assay) | How many milligrams are actually in the vial? | A measured amount compared with the label claim, usually within 90 to 110% |
| Net peptide content | Of the powder's weight, how much is peptide rather than water and salt? | Typically 70 to 90%; the rest is bound water and counter-ion |
| Counter-ion | Which salt form is it: acetate or trifluoroacetate (TFA)? | Acetate for anything injected; TFA is a synthesis leftover with tissue toxicity |
| Endotoxin (LAL) | Is it contaminated with bacterial toxins that cause fever and shock when injected? | Below the USP limit for the dose, reported in endotoxin units per milligram |
| Sterility | Is it free of living microbes? | USP <71> sterility test passed, for anything labeled sterile |
| Water and residual solvents | How much of the weight is moisture or synthesis solvent? | Reported, with limits |
Purity and quantity are different questions. A vial can be 99% pure and contain half the labeled milligrams. Quantity is the test that governs your dose, and it is the one most often missing.
- Who ran the tests? An independent, accredited lab (look for ISO 17025 accreditation and a real address) or the seller's own bench?
- Is there a lot number, a test date, and a sample description? Does the lot number match your vial?
- Is the identity confirmed by mass spectrometry, with the expected and observed masses printed?
- Is purity stated as a percentage with the HPLC chromatogram attached, or just typed?
- Is the quantity per vial measured, or only claimed? A purity number without a quantity number tells you nothing about your dose.
- Is net peptide content stated? If not, the milligrams on the label may include water and salt.
- Is the counter-ion named, and is it acetate?
- For anything injectable: are endotoxin and sterility results present, with limits?
- Does the certificate name the seller's product, or is it a supplier's certificate for raw material that has since been reconstituted, split, and re-vialed?
The one question that settles most cases
Ask the seller for the lab's contact details and permission to confirm the certificate directly. A real certificate can be verified with the lab that issued it. A fabricated one cannot, and the seller's reaction to the request is itself an answer.
- A purity of 99.9% or higher with no chromatogram. Real peptides carry synthesis impurities, and real labs show the trace.
- No lot number, or a certificate reused across products and dates. Search the image; recycled certificates turn up on several sites.
- A lab that is the seller under another name, or a lab with no accreditation, no address, and no way to verify a report.
- Purity without quantity. The seller wants you to read "99%" as "the full 10 mg."
- No endotoxin or sterility line on a product sold for injection. Chemical suppliers test purity, not fitness for injection, because their product is not meant to be injected.
- Trifluoroacetate listed as the salt, or no salt listed at all. TFA is the default output of synthesis; converting to acetate costs money and is the step a cut-rate seller skips.
None of these proves a product is bad. Each one means the certificate has not shown that it is good, which for something you are about to inject amounts to the same thing.
| Source | Who tests | What you can rely on |
|---|---|---|
| FDA-approved product | The manufacturer, under FDA inspection, every batch | Identity, purity, quantity, sterility, and stability, by law. You never see the certificate because you do not need to. |
| Licensed compounding pharmacy (503A) | The pharmacy's ingredient supplier certifies the raw material; the pharmacy controls the process under USP <797>; some pharmacies test finished batches | A regulated chain from ingredient to vial, a pharmacist to call, and a state board to complain to |
| Outsourcing facility (503B) | Facility-level batch testing under FDA's manufacturing rules | Closer to manufacturer standards; batch certificates available on request |
| Research-chemical seller | Whoever the seller chooses, if anyone | Only what an independent, verifiable certificate for your exact lot shows. Nothing else. |
A certificate does not make a research chemical a medicine
A perfect certificate proves that one sample was pure, correctly labeled, and clean on the day it was tested. It does not create a prescriber, a pharmacist, a beyond-use date, an adverse-event system, or a legal basis for sale. Those are what an approved product or a licensed pharmacy provides, and no document from a seller substitutes for them.
References
- 1.United States Pharmacopeia. General Chapter <1225> Validation of Compendial Procedures; General Chapter <621> Chromatography; General Chapter <85> Bacterial Endotoxins Test; General Chapter <71> Sterility Tests. Current editions.
- 2.U.S. Food and Drug Administration. Human drug compounding: sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act; Current Good Manufacturing Practice (21 CFR 210 and 211). https://www.fda.gov/drugs/guidance-compliance-regulatory-information/human-drug-compounding
- 3.Vergote V, et al. Quality specifications for peptide drugs: a regulatory-pharmaceutical approach. J Pept Sci. 2009;15(11):697-710.
- 4.Cornish J, et al. Trifluoroacetate, a contaminant in purified proteins, inhibits proliferation of osteoblasts and chondrocytes. Am J Physiol. 1999;277(5):E779-E783.
- 5.United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding — Sterile Preparations. 2023 revision.