How to verify a peptide vendor: COA and HPLC checklist
Before buying a research peptide, the useful question is not "is the vendor good?" but "does the vendor give me verifiable data?". A serious vendor does not ask for trust; it hands over documents you can review on your own: a per-batch Certificate of Analysis, an HPLC chromatogram, and a mass-based identity confirmation. This article is the concrete list you can use to separate a verifiable vendor from one that only makes claims. It does not cover human use, dosing, protocols, or effects.
What a real COA must contain
The Certificate of Analysis is the document that summarizes the characterization of the specific batch you bought. A verifiable COA carries, at minimum, these eight fields:
- Product name and theoretical molecular weight
- Batch number that matches the vial you received
- Reasonable analysis date and expiration date
- Analytical method used, not only a result
- HPLC purity percentage (the market standard is ≥99%)
- Molecular weight measured by mass spectrometry (MS)
- HPLC chromatogram attached or available on request
- Name of the lab that ran the analyses
A document that states "99% purity" without a chromatogram is a claim, not a verification. The guide to reading a peptide COA breaks each field down in more detail.
How to read an HPLC chromatogram
The chromatogram is the graph produced by high-performance liquid chromatography. It looks like a flat line with one or more peaks. In a pure peptide:
- The main peak should be tall, symmetrical, and well separated from the rest
- Small secondary peaks are impurities
- The purity percentage is the area of the main peak divided by the total area of all peaks
A chromatogram with several tall peaks, or with a broad and asymmetrical main peak, points to a molecule different from the one declared, or to a contaminated sample. The page on what HPLC purity is explains the method in depth.
How identity is verified by mass
Mass spectrometry (MS) confirms that the molecule in the vial weighs what it should weigh. Each peptide has a theoretical molecular weight calculated from its amino acid sequence. Tirzepatide weighs ~4,813 Da; retatrutide weighs ~4,731 Da; BPC-157 weighs ~1,419 Da. A verifiable COA reports the measured mass, and that value must match the theoretical one within a narrow tolerance.
If the COA does not mention MS, or only says "identity confirmed" without giving the numeric value, that is not an identity verification. It is a statement.
Red flags
An unverifiable vendor typically shows one or more of these patterns:
- Generic COA that does not mention the batch number, or the same COA for every vial
- Certificate with no chromatogram, only the percentage
- No lab named, or a lab that does not exist or cannot be reached
- Analysis dates that fall before the batch was produced, or after the sale date
- Product description that talks about "results", "benefits", or "protocols" in people (crossing the line from reagent to promotion as a medicine)
- Price far below the market range with no technical explanation
- Product photos but zero technical documents available on request
The Égida catalog and the RUO framework
The public Égida catalog is limited to the chemical identity of each compound. There are no human-use indications, no doses, no protocols. That profile is the operational criterion of a research reagent: describing the molecule without crossing into the medicines pathway. The explainer on the RUO and COFEPRIS framework develops that point.
Quick buyer checklist
Before you buy, check that you can answer "yes" to these six questions:
- Does the vendor deliver a COA specific to the batch I am going to receive?
- Does the COA report HPLC purity with a chromatogram?
- Does the COA report identity by mass with a numeric value?
- Does the batch number on the COA match the vial I received?
- Is the lab named on the COA a real, contactable entity?
- Is the material offered as a research reagent (RUO), with no human-use indications?
Question 4 is answered with the vial in hand and before reconstituting it: once the powder is dissolved there is no way to confirm what it was. What to check at that moment and how to calculate the concentration afterward is in the peptide reconstitution guide.
If any answer is "no", it is a red flag. It is worth pausing the purchase and asking for the missing document rather than assuming it exists. The comparator lays the catalog molecules side by side, and you can buy tirzepatide on its product page.
What a COA does not say (and why)
A COA describes the chemical identity and purity of the material. It does not say whether the compound works in people, it does not say what dose to use, and it does not say what effects it produces. That information belongs to the approved-drug label and to peer-reviewed clinical literature, not to a research reagent. A vendor that blurs those two layers (batch verification and clinical claims) is moving the product outside the RUO framework and outside the territory where the COA serves as evidence. The difference between a reagent and a medicine, with a side-by-side table, is covered in what research peptides are.