How to read a peptide certificate of analysis

A certificate of analysis (COA) is a laboratory report on one batch of a product. For a peptide it normally states what the material is, how pure it is, which tests were run, by whom and when. It is the main evidence a buyer has that a vial contains what the label says, because nobody can tell one white powder from another by looking at it.

A COA is only as good as three things: who ran the test, which tests were run and whether it belongs to the vial in your hand. The rest of this guide takes each part of a typical certificate in turn, then lists the signs of a weak or fake one. If you want to see which suppliers publish certificates at all, start with the list of suppliers that publish COAs or the narrower list of third-party tested suppliers.

The top of a certificate identifies the laboratory, the client who sent the sample, the sample itself and the date. Check each of these before reading any result.

• Laboratory name and address. It should be a real, findable organisation with its own website. A certificate printed on the supplier’s own letterhead is an in-house test, not an independent one. That is not worthless, but it is the supplier marking its own homework. Our guide to third-party testing explains the difference.
• Sample name and declared amount. For example “BPC-157, 10 mg”. The name should match the product page exactly, including variants such as CJC-1295 with or without DAC.
• Batch or lot number. This is the single most important line. It should match the batch number printed on your vial or on the product page. A certificate without a batch number could belong to any batch, from any seller.
• Dates. Look for the date the sample was received and the date the report was issued. A report dated years before the batch could have been produced is a red flag.
• Report number or verification code. Some independent labs let anyone confirm a report on the lab’s own website using a code printed on the certificate. Where that exists, use it: it is the quickest way to catch an edited PDF.

Most peptide certificates lead with a purity figure such as “99.1% (HPLC)”. HPLC stands for high-performance liquid chromatography. The sample is dissolved and pushed through a column that separates its components; a detector (usually ultraviolet light at around 214–220 nm, where peptide bonds absorb) records each component as a peak on a chart called a chromatogram. The purity figure is the area of the main peak as a share of the area of all the peaks.

Three things follow from how the number is made:

• It is relative, not absolute. HPLC purity tells you how much of what the detector can see is the main compound. It does not see water, salts or counter-ions, so a vial can be “99% pure” by HPLC and still contain noticeably less peptide than the label says. That is what net peptide content is for.
• It does not prove identity. A clean single peak shows that one compound dominates. It does not show which compound. Identity comes from mass spectrometry, covered next.
• The chromatogram matters more than the number. A good certificate includes the chart itself, with the peaks labelled and their areas listed. A purity figure with no chromatogram is a claim, not evidence.

What is a good figure? Many research-grade peptides are sold at a stated 98% or higher. Figures around 95% are not unusual for longer or harder-to-make sequences. Be more wary of a supplier whose every product is exactly 99.9% than of one whose figures vary from batch to batch: real results vary.

Mass spectrometry (MS, often run together with HPLC as LC-MS, or as MALDI-TOF) measures the mass of the molecules in the sample. Every peptide has a theoretical molecular mass that follows from its sequence. BPC-157, for example, has a molecular weight of about 1,419.5 Da. The certificate should show the observed mass next to the theoretical one, and the two should agree closely.

This is the test that catches the wrong compound, a truncated sequence, or a vial of something cheaper. A certificate that reports purity but no identity test leaves the most important question open. When you compare suppliers, a certificate with both HPLC purity and a mass result is worth much more than one with purity alone.

On a mass spectrum you will often see several peaks for one peptide: the molecule can carry more than one charge, so the same mass shows up at different mass-to-charge values. The lab normally does this arithmetic for you and reports a single deconvoluted mass.

Freeze-dried peptide powder is never 100% peptide. It also contains water and counter-ions left over from purification, most often trifluoroacetate (TFA) or acetate. Net peptide content is the share of the powder’s weight that is actually peptide. For many synthetic peptides it sits somewhere between about 60% and 90%.

This is why two “10 mg” vials can differ. One supplier may put 10 mg of powder in the vial; another may put in enough powder to deliver 10 mg of peptide. Neither is necessarily dishonest, but they are not the same product and they should not cost the same. It also changes the arithmetic in our peptide calculator, which assumes the vial holds the amount on the label.

Some labs test quantity directly: they measure how many milligrams of peptide a vial actually contains against a reference standard. A quantity result that is close to the label is one of the strongest things a certificate can show. Our guide to peptide prices explains why this matters when you compare price per mg.

Purity and identity say nothing about contamination. Fuller certificates add some of these:

• Endotoxin (LAL test). Endotoxins are fragments of bacterial cell walls. The Limulus amebocyte lysate (LAL) test measures them, usually in endotoxin units per mg (EU/mg). A low result is reassuring; a missing result simply means nobody checked.
• Sterility. Tests whether live microorganisms grow from the sample. It is slower and more expensive, so it is rarely included on research-grade certificates.
• Heavy metals. Usually measured by ICP-MS. Relevant because metals can enter during manufacture.
• Residual solvents and TFA content. Solvents and acids used in synthesis and purification can remain in the final powder.

You will not find all of these on most certificates. The point is to know what was not tested, so that a single impressive purity figure is not read as a clean bill of health.

Some certificates are simply thin. Others are edited or borrowed. These are the patterns worth checking for:

1. No batch number, or a batch number that does not match the vial or the product page.
2. The same certificate for every batch, sometimes for years. Real batches get real, separate reports.
3. A laboratory you cannot find, or one whose website does not mention peptide testing.
4. A purity figure without a chromatogram, or a chromatogram with no axes, peak table or sample name.
5. No identity test. Purity alone does not show the vial contains the named peptide.
6. Signs of editing: mismatched fonts, misaligned numbers, a date in a different typeface, or a report the lab’s own verification page does not recognise.
7. Identical results across different peptides, such as 99.9% everywhere.
8. A certificate you can only get by asking, with no public copy. Suppliers that are confident in their testing tend to publish it.

None of these proves fraud on its own, and a clean certificate does not prove a product is safe. Our broader checklist on spotting an unreliable supplier puts certificates alongside the other signals.

The strongest check you can make takes a couple of minutes. Find the laboratory’s own website independently, by searching for it rather than following a link in the PDF. If it offers an online report lookup, enter the report number or code from the certificate and compare what the lab shows with the document you were given: sample name, batch, date and results should all match. If the lab has no lookup, many will confirm by email whether they issued a report with that number.

A mismatch, or a lab that has never heard of the report, is about as clear a warning as this market gives. A match proves the report is genuine; it still does not prove your vial came from that batch, which is why the batch number on the vial matters.

• Whether your vial came from the tested batch, unless the batch numbers match.
• Whether the product was kept cold and dry between testing and delivery. See how to store peptides.
• Anything about sterility or contamination the lab did not test for.
• Whether the product is safe or suitable for any use. A certificate describes material, not an approval.

We record the certificates suppliers publish, with the laboratory, batch, test date, methods and stated purity as printed. We do not test products ourselves, and a stated purity is shown as the supplier’s or the lab’s figure, not ours. Each certificate is marked by its source: stated by the supplier, found in public, or checked by our team.

Certificates feed the transparency score on each profile, which rewards suppliers for publishing batch-matched, independent results. They do not feed the PepFinder rating, which is about the buying experience. You can see a supplier’s record in the testing and transparency section of its profile, and compare two suppliers side by side on the comparison page.