How to Read a Certificate of Analysis for Research Peptides

Quick answer: To read a Certificate of Analysis (COA) for research peptides, examine the HPLC purity percentage, confirm identity with mass spectrometry, verify the lot number matches your product, and ensure the report is from a named, independent third-party lab like Janoshik Analytical.

A vendor sends you a Certificate of Analysis, you open the PDF, and you are looking at a wall of numbers, a chromatogram, and a few lab stamps. Most researchers glance at the purity figure at the top and close the file. That is a mistake, because the parts people skip are exactly where a weak vendor hides.

A Certificate of Analysis, or COA, is the lab report on what is actually in the vial. Once you know how to read one, you can tell a real document from a decorative one in under a minute. You can see a live COA on our COA page while you read this. Here is what each part means and what good looks like.

Start with the HPLC purity percentage

High performance liquid chromatography, or HPLC, is the test that measures how pure the compound is. On the COA it shows up as a percentage, and as a chromatogram, which is the graph with one tall peak and, ideally, very little else.

The tall peak is your compound. The small peaks around it are impurities. A high purity figure means the tall peak accounts for almost all of the sample. A transparent vendor documents this per lot, not as a slogan. A figure like 99.579% on a specific Retatrutide lot, or 99.505% on a specific Tirzepatide lot, is evidence. The phrase "high purity" with no number behind it is not.

Confirm identity with mass spectrometry

Purity tells you how clean the sample is. It does not tell you what the sample is. That is the job of mass spectrometry.

Mass spec measures the molecular weight of the compound and confirms it matches the peptide you ordered. A sample can be ninety nine percent pure and still be the wrong molecule. A complete COA shows both the purity from HPLC and the identity from mass spec. If a report shows one and not the other, it is only telling you half the story.

Find the lot number tied to your vial

This is the part most people skip, and it is the one that ties the whole document to reality. Every real COA carries a lot or batch number. That number should match the batch of the product you are actually buying.

Without a lot number, a COA is just a nice looking picture. It could belong to any batch, or to none. The lot number is what stops a vendor from testing one good batch once and then attaching that same report to everything they ship for the next two years.

Check for the third-party lab

A vendor grading its own homework is not proof of anything. The signature that matters is an independent lab. In the research peptide space, that lab is most often Janoshik Analytical, which has no commercial stake in the result. We break down what it tests in our Janoshik testing guide.

An independent report carries a unique report number you can verify with the lab directly, rather than trusting a PDF at face value. That verification step is your protection against the altered documents that circulate in the space. Our full third-party testing guide walks through how to confirm one.

The red flags, in one place

Now that you know the parts, the warning signs are easy to spot. Walk away when a COA has no lot number. Be skeptical when the documentation is "available on request" instead of visible before you buy. Treat the absence of a named third-party lab as a missing signature. And never accept a generic sample document when you asked for the report on your lot.

A transparent vendor gives you exactly what this article describes without being pushed. Documentation is per batch, independent, and easy to see before any money changes hands. If verifying a whole vendor is your next question, our vendor verification checklist runs the full list.

Learn to read one COA properly and you will never again take a purity claim on faith. See a live COA and read it for yourself.

All products are for laboratory research only. Not for human or veterinary use.