How to Read a COA Without a Science Degree

For laboratory and research use only. Not for human consumption.

What Is a COA?

A Certificate of Analysis — COA for short — is basically a report card for a peptide. It is a document that tells you what was tested, what the results were, and whether the product passed.

Every legitimate peptide vendor should provide a COA for every batch they sell. If a vendor cannot give you one, that is your first warning sign. Walk away.

But having a COA is only step one. You also need to know how to read it. The good news: you do not need a chemistry degree. You just need to know which numbers matter and what they should look like.

The Key Numbers to Look At

1. Purity Percentage

This is the most important number on the entire document. It tells you what percentage of the product is actually the peptide you ordered.

What to look for:

• 98% or above is considered research-grade quality
• 99% or above is what you get from the best vendors (including us)
• Below 95% means a significant portion of what is in the vial is not the peptide — it is impurities, fragments, or other unwanted substances

The purity number comes from a test called HPLC (High-Performance Liquid Chromatography). In simple terms, HPLC separates the peptide from everything else in the sample and measures how much of the total is actually the target molecule.

2. Molecular Weight

Every peptide has a specific molecular weight — think of it like a fingerprint. BPC-157 weighs 1419.53 Daltons. Semaglutide weighs 4113.58 Daltons. If the molecular weight on the COA matches the known weight for that peptide, you can be confident the product is actually what the label says.

This number comes from mass spectrometry — a test that weighs individual molecules. A review of peptide quality standards confirmed that molecular weight verification through mass spectrometry is the primary method for confirming peptide identity (PMC10338602).

What to look for: The measured molecular weight should be within 1-2 Daltons of the theoretical weight. Exact matches are ideal, but small variations are normal due to instrument precision.

3. Appearance

This section describes what the product looks like — usually something like “white to off-white lyophilized powder” or “clear, colorless solution.”

What to look for: The description should match what you actually received. If the COA says “white powder” but you got a yellow or brown powder, something is wrong. Discoloration can indicate degradation, contamination, or a completely different product.

4. HPLC Chromatogram

Many COAs include the actual HPLC graph (called a chromatogram). This is the visual proof of purity, and it is easier to read than you might think.

What a good chromatogram looks like:

• One tall, sharp peak — this is your peptide. The taller and sharper the peak, the purer the product.
• Flat baseline — the line should be relatively flat on either side of the main peak, meaning there is very little else in the sample.

What a bad chromatogram looks like:

• Multiple peaks — extra peaks mean extra substances. Some small peaks are normal (no synthesis is perfect), but many peaks or large secondary peaks indicate significant impurities.
• Noisy, wavy baseline — suggests the sample is messy or the testing was poorly done.

5. Mass Spectrum Data

If the COA includes mass spec data, it will show a peak at the molecular weight of the peptide. This is your identity confirmation — proof that the molecule in the vial is the molecule on the label.

What to look for: A clear peak at the expected molecular weight. Some COAs show multiple peaks due to the way mass spec works (the molecule can carry different charges), but the dominant peak should correspond to the correct weight.

Red Flags on a COA

Not all COAs are trustworthy. Here are the warning signs that a COA might be fake, recycled, or unreliable:

• No lab name — A real COA identifies the laboratory that performed the testing. If there is no lab name, there is no way to verify the results.
• No date — Testing results should be dated. An undated COA could be years old or copied from a different batch.
• No batch or lot number — Without a batch number, you cannot confirm that the COA corresponds to the specific product you received. The vendor might be reusing one good COA for every batch they sell.
• Suspiciously perfect numbers — A purity of exactly 100.00% should raise an eyebrow. Even the best synthesis and purification processes produce some trace impurities. Real results have decimal places and minor imperfections.
• No chromatogram or spectrum — A COA that lists numbers but does not include the actual graphs is harder to verify. The raw data is what proves the numbers are real.
• Generic or templated appearance — If the COA looks like it was made in Microsoft Word with no lab branding, it probably was.

How to Verify a COA Is Real

If you want to go the extra mile, here is how to check that a COA is legitimate:

1. Look up the lab — Search for the laboratory name online. Does it have a website? Does it look like a real analytical lab? Does it list peptide testing among its services?
2. Contact the lab — Call or email the lab listed on the COA. Ask them to confirm that they tested a batch with that specific batch number on that date. A legitimate lab will confirm or deny.
3. Compare batch numbers — The batch number on the COA should match the batch number on your product label. If they do not match, the COA was not generated for your product.
4. Ask the vendor for the raw data file — HPLC instruments generate digital data files. A vendor who can provide the original data file (not just a PDF or screenshot) has nothing to hide.

What NorthPeptide COAs Include

Every COA we provide includes the lab name, testing date, batch number, HPLC purity percentage, HPLC chromatogram, mass spectrometry confirmation, and product appearance verification. Our testing is performed by independent third-party laboratories — not our own in-house lab.

For more on our testing process, read: How We Test Our Peptides: Our Quality Process Explained.

For details on our purity guarantee, visit our guarantees page.

Summary of Key Research References

Topic	Reference	PMC ID
Reference standards for peptide therapeutics	Bak et al., Journal of Pharmaceutical Sciences, 2023	PMC10338602
HPLC analysis and purification of peptides	Mant & Hodges, Methods in Molecular Biology, 2008	PMC7119934
Peptide impurities in commercial products	Currier et al., Clinical and Vaccine Immunology, 2008	PMC2238048
Regulatory guidelines for peptide analysis	Various, Pharmaceuticals, 2025	PMC11806371

Written by NorthPeptide Research Team

For laboratory and research use only. Not for human consumption.