Buying

How to read a peptide COA (certificate of analysis)

Reviewed by the amino101 editorial team. Last updated October 12, 2026.

A peptide COA, or certificate of analysis, is a lab report for one batch of product, and a useful one has five things: an HPLC purity figure, a mass spectrometry identity check, a lot number that matches your vial, the name of an independent lab, and a date. Quantity and endotoxin results make it better. Most grey market certificates have the first item and little else, which is why a 99 percent purity figure on its own is close to meaningless.

This guide goes line by line through what each test measures, what it cannot tell you, how to confirm a certificate with the lab that issued it, and the red flags that mark a certificate as decoration. It is the companion to how to buy peptides and to the six checks on the vendor page, where published, verifiable COAs are the first two criteria.

Key points

•HPLC purity is a ratio of peptide to impurities; it says nothing about how much peptide is in the vial or whether it is the right one.
•Mass spectrometry confirms identity by molecular weight; a COA without it could be a pure sample of the wrong compound.
•A 99 percent pure vial can hold 6 mg instead of 10; only a quantity or net content result catches that.
•Endotoxin (LAL) and sterility are separate tests that most research COAs skip, so those risks are unknown unless reported.
•A COA needs a lot number, a named lab and a date; check it with the lab, not the vendor.

What a peptide COA is and what it should contain

A certificate of analysis is a report from a testing lab describing the results of specific tests on a specific sample. For a peptide, the sample is a vial from one manufacturing lot, and the certificate speaks only for that lot. It is not a general statement about the vendor, the product line or any vial from a different batch. That is the first thing to internalize, because the most common misuse of a COA is treating a single good result as a permanent credential.

The elements that make a certificate worth reading are listed below. A certificate missing the first four is not evidence of anything; a certificate with all seven is as good as the grey market gets.

•Product name and expected sequence or molecular weight, so you can check the identity result against it.
•Lot or batch number, printed on both the certificate and the vial label.
•Name and location of the testing lab, with a way to contact it.
•HPLC purity, as a percentage, with the chromatogram or at least the method stated.
•Mass spectrometry result, the observed mass against the expected mass.
•Quantity or net content per vial, in mg, if the vendor paid for it.
•Endotoxin (LAL) and sterility results, if the vendor paid for them.
•Date of analysis and a signature or report number.

HPLC purity on a peptide COA: what the number means and does not mean

HPLC, high performance liquid chromatography, pushes the dissolved sample through a column that separates components by their chemistry. Each component comes out at a different time and registers as a peak. The purity figure is the area of the main peak divided by the area of all peaks, which means it answers one question: of the peptide-like material in this sample, what share is the main compound rather than fragments, deletion sequences and synthesis byproducts? Reputable research peptides typically show 98 percent or higher.

It does not answer three other questions. It does not tell you how much material is in the vial, because the ratio is the same whether the vial holds 3 mg or 10. It does not tell you the main peak is the right peptide, because a different compound with similar chemistry produces a similarly clean peak. And it does not see things that are not peptides: water, salt, residual solvents and endotoxin are invisible to a standard HPLC purity run. A vendor who leads with 99.4 percent purity is reporting the easiest and least informative number on the certificate.

A good certificate shows the chromatogram itself, not just the figure. A single sharp peak with small satellites is what a clean peptide looks like. Several large peaks, or a broad smeared main peak, mean trouble even when the arithmetic still comes out above 95.

Mass spectrometry identity: the second half of the COA

Mass spectrometry measures the molecular weight of what is in the sample. A peptide has a known mass from its sequence; BPC-157, for example, is 1419.5 daltons. The certificate should show an observed mass and the expected mass, and they should match within a small tolerance. That is the test that says the clean peak on the HPLC trace is the compound on the label and not something else.

Paired, HPLC and mass spec form the core of a credible certificate: one says it is pure, the other says it is the right thing. A certificate with HPLC alone could be describing a very pure sample of the wrong peptide, and this is not hypothetical; mislabeled vials where one compound was sold as another are documented across the research market. Mass spec is the cheaper of the two tests in most labs, so its absence is a choice.

Quantity vs purity: the 6 mg in a 10 mg vial problem

Here is the gap most buyers never think about. A vial labeled 10 mg at 99 percent purity can contain 6 mg of peptide, and both numbers are true: the 6 mg is 99 percent pure. Purity is a ratio. Quantity is a weight. Lyophilized peptide also carries water and counter ions, acetate or trifluoroacetate from synthesis, that can account for 10 to 30 percent of the powder's mass even in a well made product, so a vial that was filled by weight of crude powder may hold noticeably less active peptide than the label suggests.

The test that catches this is a quantity or net content assay, often done by quantitative HPLC against a reference standard or by amino acid analysis, and reported as mg per vial. It costs more and most grey market vendors do not pay for it. When a vendor does, it is the strongest single signal on the certificate, because underfilling is the cheapest way to cut costs and the hardest for a buyer to detect without a lab. A vial that seems to work less well than the last one is often this, not degradation.

If the certificate shows only purity, assume you do not know how much is in the vial. The compound pages' dose ranges and the calculator treat the label as true because there is no alternative, but the uncertainty is real.

Purity tells you the quality of what is there. Quantity tells you how much is there. A vendor quoting only purity has answered the question that was not asked.

Endotoxin, sterility and what a research COA usually skips

Endotoxins are fragments of bacterial cell walls that remain after bacteria are dead and even after a solution is sterile filtered. Injected, they cause fever, chills and inflammation, and at high enough levels worse. The pharmaceutical test is the LAL assay, using an extract of horseshoe crab blood that clots in the presence of endotoxin, and it is reported in endotoxin units per mL or per mg. Every approved injectable is tested for it. Most research peptide certificates are not, which means the endotoxin level of most grey market vials is simply unknown.

Sterility is a separate question again, tested by culturing the product and looking for growth. Lyophilized powder that was made under reasonable conditions and reconstituted with bacteriostatic water is usually fine in practice, which is why the research market has not produced more disasters than it has. But usually fine is a statement about odds, not about your vial. A vendor who publishes LAL results is spending money on your behalf that most competitors do not, and that is worth noticing.

Lot numbers, lab names and verifying a COA with the lab

The lot number ties the certificate to the vial. It should appear on the certificate and on the vial label, and they should match. A certificate without a lot number cannot be tied to anything, and a vendor who posts one certificate per product rather than per lot is showing you a sample result from some batch at some point in the past. The second element is the lab. It needs a name, a location and a way to contact it, and it needs to exist. Cropping the lab name off a certificate is a hard no on the vendor page for a reason.

Verification is a short process. Find the lab's own website, not a link from the vendor. Contact them with the report number or lot number from the certificate and ask whether they issued it and whether the results match. Independent labs serving this market generally confirm reports, and some run lookup pages by report number. A lab that does not respond, has no public presence, or shares an address with the vendor is not independent. The certificate is then the vendor's word in a different font.

Dates matter too. A certificate from two years ago for a lot that is still shipping means either very slow sales or a certificate being reused across lots. Either way, ask.

Peptide COA red flags

Each of these on its own is a reason to ask the vendor a question. Two or more together are a reason to buy elsewhere.

•No lot number, or a lot number that does not match the vial.
•The same certificate on every product, or the same purity figure across every lot.
•No lab named, the lab name cropped or blurred, or a lab that cannot be found outside the vendor's site.
•In-house testing presented as third party.
•An image-only certificate with no report number, no method, and no chromatogram, which could have been made in any graphics program.
•HPLC only, with no mass spectrometry identity result.
•Suspiciously round or suspiciously perfect purity, such as 100 percent or 99.99 percent, with no trace shown.
•Available on request rather than published, followed by a certificate that arrives without any of the above.

A worked example: reading a sample peptide COA

The table shows the kind of result block a good certificate carries for a 10 mg vial of BPC-157, and how to read each line. The numbers are illustrative.

Line on the COA	Example result	How to read it
Product	BPC-157 acetate, lot 24-0917	Lot must match the vial
Expected mass	1419.5 Da	From the sequence; the reference for identity
Observed mass (MS)	1419.7 Da	Within tolerance; identity confirmed
HPLC purity	98.9 percent	Share of peptide material that is the main peak
Net content	9.6 mg per vial	The actual amount; close to label
Endotoxin (LAL)	Under 1 EU per mg	Low; suitable for the intended research use
Lab	Named lab, city, report number	Contact the lab to confirm the report
Date	Within the last year	Recent enough to belong to this lot

Nothing on a COA tells you a compound is safe or effective in people. It tells you what is in the vial. Are peptides safe covers the other half.

Frequently asked

What is a COA for peptides?

A certificate of analysis is a lab report on one batch of product showing purity by HPLC, identity by mass spectrometry, and ideally quantity and endotoxin. It should carry a lot number matching your vial and the name of an independent lab.

What does 99 percent purity mean on a peptide COA?

That 99 percent of the peptide-like material in the sample is the main compound, measured by HPLC peak area. It does not mean the vial holds the labeled amount, that the main peak is the right peptide, or that the product is free of endotoxin.

How do I verify a peptide COA is real?

Find the lab's own website independently, contact them with the report or lot number, and ask whether they issued it. A lab that cannot be found, does not answer, or shares an address with the vendor is not independent.

What is the difference between purity and quantity on a COA?

Purity is a ratio of peptide to impurities. Quantity is the weight of peptide in the vial. A 99 percent pure vial can hold 6 mg when the label says 10; only a net content result reveals that.

Do peptide COAs test for endotoxin?

Most grey market certificates do not. The LAL test is standard for pharmaceutical injectables and reported in endotoxin units. A vendor who publishes LAL results is paying for a test most competitors skip.

Is a COA from the vendor's own lab acceptable?

Not as third party testing. In-house results are the vendor checking its own work. The vendor page's first criterion is testing by an independent, named lab that you could contact, and the same standard applies to any vendor you vet yourself.

Sources

Bacterial Endotoxins Test, General Chapter 85. United States Pharmacopeia, 2023
ANDAs for Certain Highly Purified Synthetic Peptide Drug Products That Refer to Listed Drugs of rDNA Origin (guidance). US Food and Drug Administration, 2021
Validation of Analytical Procedures: Text and Methodology Q2(R1). International Council for Harmonisation, 2005
Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products Q6B. International Council for Harmonisation, 1999

Educational only. Dose ranges describe what appears in published research and community protocols. This is not medical advice and most of these compounds are not approved for human use. Talk to a clinician who knows your history.