A certificate of analysis (COA) is the sole document that transforms a vial of white powder into a verifiable research material. Without one, there is no way of knowing if the compound within a vial is what the label says, or how much of it is present. But many COAs within the research peptide market are incomplete, reused across batches or simply fabricated, and independent research has found that products labeled at 98% or higher purity are often tested far below in practice.
This guide will show you how to read a peptide COA line by line, what each test shows and which red flags should stop an order before your vial arrives at your bench.
What is a peptide COA?
A COA is a laboratory report tied to a specific production lot, which records which tests were run on that lot, which laboratory ran them, when they were run and what the results were. A good peptide COA answers two core questions: Is this the right molecule? and How pure is it? Good COAs also answer a third: Are there any other contaminants that would affect my experiment?
At Wolverine Peptide, every order ships with a COA that matches the batch in the box. It is never a generic purity claim reused for different lots.
Step 1: Match the lot number
Start here, before you look at any result. The lot or batch number printed onto the vial label must appear on the COA. If it doesn’t, the report says nothing about the vial in your hand, no matter how impressive the numbers are.
This is important because peptide synthesis is variable perbatch, and a COA from a previous lot, even from the same supplier, can’t confirm the quality of the lot you received. Keep record of lot numbers for every vial used in your study, so that results can be traced back in the event of questions.
Step 2: Check HPLC purity
High-performance liquid chromatography (HPLC) is the standard test on peptide purity. It pushes the sample through a column that separates its components and reports the target peptide as a percentage of everything detected.
What to look for:
A purity of 98-99% or above. This is the standard for research-grade material.
An actual chromatogram, not just a typed number. You should see one large, dominant peak for the peptide and only small minor peaks. Those smaller peaks are impurities, such as truncated or incomplete sequences left over from synthesis.
Method details. Column type, mobile phase and detection wavelength should be listed. UV detection around 214-220 nm is standard for peptides.
Consistent retention time. The time the peptide takes to pass through the column should be consistent for batches of the same compound.
Step 3: Confirm identity with mass spectrometry
HPLC tells you how pure a sample you have. It doesn’t tell you what the sample is. A sample could be 99% pure of the wrong molecule and an HPLC alone would never reveal it. A peptide missing a single amino acid can appear highly pure on HPLC and be a different compound altogether.
That’s why mass spectrometry (MS) is essential – it measures the molecular weight of what’s in the sample. What the COA should list are two figures:
Theoretical mass, calculated from the peptide’s known amino acid sequence
Observed mass, measured by the instrument
The two numbers should match closely, usually around about ±1 Dalton. If they don’t match, then the vial doesn’t contain the peptide on the label. A COA that shows HPLC purity but no mass spec is a half report.
Step 4: Look for endotoxin testing
Endotoxins are fragments of the outer membrane of certain bacteria. They can be introduced during manufacturing or handling, and they are invisible to both HPLC and mass spec.
This is important because endotoxins can trigger strong inflammatory responses in cell cultures and animal models. In tissue repair and inflammation research, this can directly skew results and give an appearance of function when there isn’t any. Endotoxin screening is one of the most commonly missing tests on commercial research peptide COAs. If your work is cell-based or in vivo, it’s essential instead of optional.
Step 5: Understand purity vs net peptide content
These two figures are often confused, even by suppliers:
| Term | What it measures | Typical range |
| HPLC purity | Target peptide vs. peptide-related impurities | 98–99%+ |
| Net peptide content | Peptide vs. everything in the vial, including water, salts, and counter-ions | Often 70–85% |
Lyophilized powder will always contain some bound water and counter-ions that are left over from purification. HPLC purity doesn’t measure these, and a vial can be 99% pure and still contain noticeably less than its label weight in actual peptide content. If precise concentration matters for your study, ask for the net peptide content figure.
Step 6: Check who tested it and when
A credible COA names an independent testing laboratory, not the seller’s own bench. Third-party testing is important because the lab has no vested interest in the result. The report should also include a recent analysis date that matches the batch, and ideally a way to verify the report directly with the lab (such as a verification code).
Red flags of a fake or weak COA
No lot number, or a lot number that doesn’t match the vial
A purity figure without a chromatogram or mass spectrum attached
An observed mass that doesn’t match the peptide’s theoretical weight
Numbers that look typed over the graph or edited
The same COA for every batch, or every product
Analysis dates that are old or don’t match the batch
No named laboratory, or only the seller’s in-house lab
Willingness to share a COA only after purchase
Quick COA checklist
Lot number on vial = lot number on COA
HPLC purity ≥98-99% with chromatogram shown
Mass spec observed mass matches theoretical mass
Endotoxin result reported
Independent lab named, with a recent date
How Wolverine Peptide handles COAs
Every vial of our BPC-157 and TB-500 comes from a single tested lot. The COA issued with your order includes HPLC purity, mass spec sequence confirmation and endotoxin screening for that exact batch. You can read more about our testing standards on the About page.
A good COA also assumes that the vial was handled correctly after testing. Heat and moisture can degrade a peptide long after the lab report was issued, so see our peptide storage guide for what to do once it arrives. New to these compounds? Start with the Wolverine stack explained, or read where to buy Wolverine peptides.
FAQ
What purity should a research peptide have?
Most suppliers and labs consider 98-99% HPLC purity the minimum for research use.
Can HPLC alone confirm a peptide?
No. HPLC measures purity, and mass spectrometry confirms identity. You need both.
Why is net peptide content lower than purity?
Lyophilized powder will also contain water, salts and counter-ions, which HPLC purity doesn’t measure.
Should I ask for a COA before ordering?
Yes. A reputable supplier will share the batch COA before or with your order.