How to Read a COA

TL;DR

- A Certificate of Analysis (COA) is a lab document that reports two separate things about a batch of material: its identity (is this the molecule it claims to be?) and its purity (how much is the target versus impurities?). - Identity is usually confirmed by mass spectrometry (MS), which measures molecular weight in Daltons and compares it to the peptide's expected mass. Purity is usually measured by high-performance liquid chromatography (HPLC), reported as area percent of the main peak. - A figure like "98%+" only means something when it names the method and shows the actual chromatogram, and area percent is not the same as net peptide content by weight. - A third-party COA comes from an independent lab that ran the tests. A supplier's own "98% pure" line on a label is a marketing statement unless independent data backs it. - Research-grade peptides are not the regulated pharmaceutical products studied in trials such as STEP 1 (Wilding et al., 2021) or SURMOUNT-1 (Jastreboff et al., 2022), so a COA is one of the few objective checks a buyer has.

What is a Certificate of Analysis (COA)?

A COA is a document that reports the results of laboratory tests run on one specific batch of material.

It answers two core questions: what is this compound (identity), and how pure is it (purity and content). A useful COA is tied to a batch or lot number, names the tests and the methods used, and shows the underlying data, not just a summary line. For research peptides, the difference between a strong COA and a weak one is whether you can see the raw evidence: the chromatogram and the mass spectrum. Anything less is a claim, not a report.

What does a COA test on a research peptide?

A good COA reports identity, purity, and often quantity using named analytical methods, and may add endotoxin or moisture results depending on the material.

Here is how the common sections map to the tests behind them. These are standard analytical-chemistry methods, described here so you can recognize them on a report.

Not every COA includes every row. A basic report may show only identity and purity. A fuller report adds content, endotoxin, and moisture.

How does mass spectrometry confirm a peptide's identity?

Mass spectrometry measures the molecular weight of the compound and checks it against the mass the target peptide should have.

Every peptide has a theoretical mass set by its amino acid sequence. MS ionizes the sample and measures the mass-to-charge ratio, giving an observed mass in Daltons. If the observed mass matches the expected mass within a small tolerance, that supports the identity claim. If the mass is off, the material may be the wrong sequence, a truncated or incomplete peptide, or something else entirely. Keep in mind what MS does and does not do: it confirms what the molecule is, not how much of it is present and not how clean the sample is. Those are different questions answered by other tests.

What does an HPLC purity figure like 98%+ mean?

An HPLC purity of 98 percent means the target peptide accounts for about 98 percent of the detected material by peak area, leaving about 2 percent as related impurities.

Reverse-phase HPLC pushes the dissolved sample through a column so the components separate and come off at different times, each showing up as a peak. Purity is the area of the main peak divided by the total area of all peaks, written as a percent. Three points matter when you read that number:

- Area percent is a relative measure of what the detector saw at a chosen wavelength. A purity figure with no method and no chromatogram is hard to trust, because you cannot see what was actually separated. - Area percent is not the same as net peptide content. A vial can read "98 percent pure" by HPLC and still contain counterion salts (such as acetate or trifluoroacetate), water, and residual solvent, so the amount of actual peptide by weight can be lower than the label. Net peptide content is a separate figure. - "98%+" is an advertised convention in the research peptide market. It is meaningful only alongside the supporting data.

What is endotoxin testing, and when does it show up on a COA?

Endotoxin testing measures bacterial endotoxin, a contaminant from certain bacteria, and appears on COAs for materials where contamination could matter for the intended laboratory use.

The common test is the LAL assay (Limulus amebocyte lysate), with results in endotoxin units (EU), often given per milligram. Lower numbers mean less endotoxin was detected. Endotoxin testing is separate from identity and purity: a batch can be the right molecule at high purity and still be a topic worth checking for contamination. Simpler research COAs often leave endotoxin off entirely, so its absence on a report is not automatically a problem, but its presence tells you the lab looked.

How is a third-party COA different from a supplier's own claim?

A third-party COA is issued by an independent lab that ran the analysis, while a supplier's own claim is a statement from the seller that may or may not be backed by independent data.

The gap between the two is about who did the work and whether you can check it.

An independent report is not automatically perfect, and a supplier claim is not automatically wrong. The point is verifiability: a report you can trace to a lab, a date, a method, and a batch is far stronger evidence than a number printed on a label.

What should raise a red flag on a COA?

Treat a COA with caution when it lacks the data that would let you check the result yourself.

Watch for these:

- A purity percent with no chromatogram and no named method. - No batch or lot number, so the report is not tied to anything specific. - No test date and no lab identity. - Identity "confirmed" with no mass spectrum shown. - A compound name or mass that does not match the target peptide. - A "COA" that is really just the product label restated in a document.

Why does COA verification matter for research peptides specifically?

Because research-grade peptides are sold for laboratory use and are not the regulated pharmaceutical products studied in clinical trials, so their identity and purity are not guaranteed by any approval process.

Semaglutide and tirzepatide, the compounds behind results like about 15 percent mean weight loss in STEP 1 (Wilding et al., 2021) and up to about 22.5 percent in SURMOUNT-1 (Jastreboff et al., 2022), were tested as regulated pharmaceutical products made under controlled manufacturing, not as research-grade powder. Research-grade material carries no such guarantee. For many compounds, human data is limited: published human evidence for BPC-157, for example, is very limited and animal studies dominate. A COA does not make a research peptide safe or effective. It tells you what the material is and how pure the tested batch was. Those are two different questions, and a COA answers the first, not the second. Any question about personal use belongs with a qualified clinician.