What Is a Certificate of Analysis?
A Certificate of Analysis — usually just called a COA — is a document from a laboratory that reports the results of testing performed on a specific batch of a substance. In the context of research peptides, it tells you two fundamental things: what the peptide is (identity) and how pure it is (purity).
If you’re purchasing peptides for research, the COA is the single most important document you should be reviewing. It’s the difference between knowing what’s in your vial and just hoping. And yet, most people either skip it entirely or glance at the number on top without understanding what they’re actually looking at.
This guide breaks down every section of a peptide COA so you can evaluate quality for yourself — no chemistry degree required.
Why COAs Matter for Research
Research results are only as reliable as the materials used to produce them. A peptide with 85% purity contains 15% of something else — truncated sequences, deletion peptides, salts, residual solvents, or other synthesis byproducts. Those impurities can introduce confounding variables, alter binding affinity, or produce inconsistent results between experiments.
Published studies routinely specify the purity of compounds used, and for good reason. If you can’t verify what you’re working with, your results aren’t reproducible. A COA is how you verify.
Third-Party vs. In-House Testing
This is the first thing to check, and it’s the most important distinction most people overlook.
In-house testing means the company that manufactured or sells the peptide also tested it. That’s like grading your own homework. It doesn’t mean the results are wrong — but there’s an obvious conflict of interest. Equipment calibration, methodology, and reporting standards vary wildly between in-house labs.
Third-party testing means an independent laboratory with no financial interest in the outcome performed the analysis. The gold standard is an ISO 17025 accredited lab — this is an international standard that certifies the lab’s testing competence, equipment calibration, quality management systems, and reporting accuracy.
At Chameleon Peptides, every batch is tested by Janoshik Analytical, an ISO 17025 accredited laboratory based in the Czech Republic. We don’t test in-house. We send samples to the same independent lab that the broader research community trusts, and we publish the results.
What to look for
- Lab name and logo — Is there an identifiable third-party lab on the document?
- Accreditation — Does the lab hold ISO 17025 or similar certification?
- Sample ID / batch number — Does the COA reference a specific batch, not just a generic product?
- Date of analysis — When was the test actually performed?
If a COA doesn’t clearly identify the testing laboratory, or if the lab is the same company selling you the product, weigh that accordingly.
HPLC Purity: The Core Number
HPLC stands for High-Performance Liquid Chromatography. It’s the primary method used to determine peptide purity, and the purity percentage on a COA almost always comes from this test.
How it works (simplified)
A dissolved sample of the peptide is pushed through a column packed with tiny particles. Different molecules travel through the column at different speeds depending on their chemical properties — size, charge, and how they interact with the column material. As each molecule exits the column, a detector measures it.
The result is a chromatogram — a graph with time on the x-axis and signal intensity on the y-axis. Each compound in the sample produces a peak. The target peptide should appear as one dominant peak, and the area under that peak relative to all other peaks gives you the purity percentage.
Reading the chromatogram
A clean chromatogram has:
- One large, sharp main peak — this is your peptide
- Minimal smaller peaks — these are impurities (synthesis byproducts, truncated sequences)
- A flat baseline — indicates low background noise and clean separation
When a COA reports “99.2% purity by HPLC,” it means that 99.2% of the total peak area on the chromatogram belongs to the target peptide. The remaining 0.8% is everything else.
What the method details tell you
A thorough COA will include HPLC method parameters. You don’t need to memorize these, but knowing what they mean helps you evaluate quality:
- Column type — usually a C18 reversed-phase column for peptides
- Mobile phase — the solvents used (typically water and acetonitrile with a small amount of trifluoroacetic acid)
- Flow rate — how fast the solvent moves through the column (usually 1.0 mL/min)
- Detection wavelength — typically 220 nm for peptides, which detects the peptide bond
- Gradient — how the solvent ratio changes over time to separate different compounds
The presence of these details is itself a quality signal. A COA that just says “99% pure” without any method information gives you less to verify.
Mass Spectrometry: Identity Confirmation
HPLC tells you how pure something is. Mass spectrometry (MS) tells you what it is.
Here’s why both matter: a peptide missing one amino acid could appear as a single clean peak on HPLC and report as 99% pure. But it’s the wrong peptide — or at least, it’s not the one you ordered. Mass spectrometry catches this.
How it works (simplified)
The peptide is ionized (given an electrical charge) and sent through a mass analyzer that separates molecules by their mass-to-charge ratio. The result is a mass spectrum — a graph showing the masses of molecules detected in the sample.
What to look for
- Observed mass vs. theoretical mass — the COA should list both. The observed mass should match the theoretical (expected) molecular weight of the peptide within ±1-2 Daltons. A Dalton (Da) is the unit of molecular mass.
- Dominant peak at the correct mass — the mass spectrum should show a clear, dominant signal at the expected molecular weight
- Charge states — peptides often appear at multiple charge states (e.g., [M+H]⁺, [M+2H]²⁺). This is normal and expected.
If the observed mass is off by more than a couple of Daltons, that’s a red flag — it could indicate a deletion peptide (missing amino acid), an oxidized form, or an entirely different compound.
Other Tests You Might See
Beyond HPLC and MS, some COAs include additional quality metrics:
Appearance
A physical description of the product — typically “white to off-white lyophilized powder” for research peptides. This is basic but useful: if a peptide that should be a white powder arrives as a yellow clump, that’s worth noting.
Peptide content
This is different from purity. Peptide content (sometimes called “net peptide content”) accounts for the presence of counter-ions (like acetate or TFA salts) and moisture. A peptide can be 99% pure by HPLC but have only 80% peptide content — the other 20% being salts and water that co-lyophilize with the peptide. This matters for accurate weighing in research.
Amino acid analysis
The peptide is broken down into its individual amino acids and each one is quantified. This confirms the amino acid composition matches what’s expected. It’s a more expensive test and not always included, but it provides another layer of identity verification.
Endotoxin testing
Measures bacterial endotoxin levels, important for certain types of cell culture and in vivo research. Usually reported in EU/mg (endotoxin units per milligram).
Water content (Karl Fischer)
Measures residual moisture in the lyophilized product. Lower moisture content generally correlates with better long-term stability.
Red Flags: When a COA Doesn’t Add Up
Not all COAs are created equal. Here are warning signs that should make you look more closely:
- No lab identified — if you can’t tell who performed the testing, the document is essentially meaningless
- Round numbers across all products — if every single product from a vendor is exactly 99.0% pure, that’s suspiciously uniform. Real analytical results have variation (99.2%, 98.7%, 99.5%)
- No chromatogram — the purity number without the chromatogram is a claim without evidence
- No mass spectrum or molecular weight data — purity without identity confirmation means you know something is pure, but you don’t know what it is
- Missing batch/lot number — a COA should be tied to a specific batch. A generic COA for a product suggests it might not represent what you’re actually receiving
- Outdated dates — if the test date is years old but the product is listed as new stock, the COA may not reflect the current batch
- Template inconsistencies — differences in formatting, fonts, or logos between COAs from the same “lab” can indicate document fabrication
How Chameleon Peptides Handles Testing
We send every batch to Janoshik Analytical before it goes on sale. The COAs on our site are the actual reports from Janoshik — not edited, not summarized, not reinterpreted. Each one includes:
- HPLC purity with full chromatogram
- Mass spectrometry data with observed and theoretical molecular weights
- Batch-specific identification
- Date of analysis
- Janoshik’s laboratory identification and accreditation
We publish them because transparency shouldn’t be optional. If a vendor won’t show you the actual lab report — chromatogram included — ask yourself why.
A Quick Checklist
Next time you’re reviewing a COA, run through these questions:
- Who tested it? — Independent lab or in-house?
- Is the lab accredited? — ISO 17025 or equivalent?
- What’s the purity? — ≥98% is the general benchmark for research-grade peptides
- Is there a chromatogram? — Can you see the actual HPLC trace?
- Is identity confirmed? — Mass spec data showing the correct molecular weight?
- Is it batch-specific? — Does it reference the specific lot you’re receiving?
- When was it tested? — Recent enough to be relevant?
If you can answer yes to all seven, you’re working with a vendor that takes quality seriously.
The Bottom Line
A COA isn’t a marketing document — it’s a quality control record. Learning to read one takes about ten minutes. That small investment protects every experiment you run with the material.
All of our certificates of analysis are available on our testing page. If you have questions about a specific COA or want to understand a result in more detail, reach out to us — we’re happy to walk through it.