The FDA spent two days in July arguing that these compounds cannot be reliably identified or compared across sources. That is not a regulatory abstraction — it is a description of the vial on your desk. A certificate of analysis is the only tool a buyer has, and most people read them wrong.
This is a framework for evaluating documents. We do not lab-test products, we do not publish purity rankings, and we will never present a score we did not generate through a documented process. What follows is how to interrogate a COA yourself — which is more durable than any list we could publish.
The four questions, in order
1. Does the lot number match?
Start here, because it invalidates everything else. A COA is a report on one batch. If the document is headed with a lot number and your vial is labeled with a different one, you are reading a report about someone else's material.
The common failure mode is not fraud — it is a vendor posting a single PDF on a product page and leaving it there through two years of restocks. Ask for the COA for your lot specifically. A supplier with real testing discipline sends it. A supplier without one changes the subject.
2. Who ran the test?
An in-house COA on the vendor's own letterhead is a self-report. It may be perfectly accurate. It is not independent. Look for a named third-party laboratory with its own contact details on the document — and be aware that a vendor logo pasted on top of lab output is not the same as a lab-issued report.
3. What methods were run?
| Method | What it answers | What it does not |
|---|---|---|
| HPLC | Purity — what fraction is the main peak | Whether that peak is the right molecule |
| Mass spectrometry | Identity — molecular weight confirmation | How much of the vial is peptide |
| Peptide content | How much of the mass is actually peptide | Purity or identity |
| Endotoxin / sterility | Contamination screening | Anything about the peptide itself |
The pattern worth internalizing: purity, identity, and content are three separate questions. A COA showing 99% HPLC purity with no mass spec is telling you the material is consistent without telling you what it is. Given the FDA's own stated objection about chemical characterization across this whole category, identity confirmation is not a nice-to-have.
4. What is the peptide content number?
This is the most commonly omitted figure and often the one that matters most economically. A lyophilized vial contains peptide plus counterions, residual solvent, and water. Peptide content — sometimes reported as net peptide content — tells you what fraction of the labeled mass is the actual compound.
Two vials both reporting 99% purity can differ substantially in how much peptide they contain. If a COA reports purity but not content, you know less about what you paid for than you think.
Red flags that should end the transaction
- No lot number anywhere on the document. A COA without a lot identifier is not a COA.
- An undated report. Analysis has a date. Its absence is a choice.
- Image-only PDFs with no lab letterhead. Trivially fabricated, and everyone knows it.
- Purity figures with no method stated. 99% by what measurement?
- A single COA covering multiple products. Batch testing does not work that way.
- Refusal to provide a lot-specific document on request. This is the answer.
FDA career reviewers recommended against adding all seven nominated peptides to the 503A bulks list, and their lead objection was chemical characterization — the argument that without accepted definitions, identity, quality, and lot-to-lot comparability cannot be established. The advisory committee voted against staff on six of seven anyway. Whatever you think of the vote, the underlying technical objection was correct and it applies with full force to research-channel material.
What a good supplier relationship looks like
You ask for the COA for lot number X. You receive a dated third-party report bearing that lot number, showing HPLC purity, mass spec identity confirmation, and peptide content, on the laboratory's own letterhead with contact details. It takes them under a day because they already have it filed.
That is the whole standard. It is not exotic and it is not rare among suppliers who take the category seriously. It is simply absent among those who do not, which makes it an efficient filter.
Suppliers that publish batch documentation
Frequently Asked
A document from an analytical laboratory reporting what testing was performed on a specific batch of material and what the results were. At minimum it should identify the compound, the lot, the methods used, and the measured purity.
Whether the lot number on the COA matches the lot number on the vial you received. A generic product-line COA tells you what some batch looked like at some point. It tells you nothing about yours.
No. HPLC tells you about purity — what fraction of the material is the main peak. It does not confirm identity. Mass spectrometry is what establishes that the main peak is actually the molecule on the label. A COA with purity data and no identity confirmation is answering half the question.
It means roughly 99% of what the detector saw at the chosen wavelength was one peak. It does not speak to peptide content (how much of the vial mass is actually peptide versus salts and residual water), and it does not confirm what that peak is. Peptide content is frequently the larger real-world variable and is frequently omitted.
Yes, unambiguously. Publishing third-party analysis is the lowest bar in this category and it costs the supplier real money per lot, which is exactly why it is a meaningful signal.