Quick answer
Identity tells you what the material is. The result figure tells you how much of what the method detected is that compound. They're different measurements, and a complete record reports both for the same lot.
A COA can look like a single verdict, but it's really answering two questions. What is this material? And how much of it is the stated compound?
Those two questions are identity and purity. They're easy to mix up when you're reading a record. This guide walks through each one, and why a record that has only one of them is incomplete.
If COAs are new to you, How to Read a Peptide COA is a good place to start.
Two separate questions on one COA
A complete COA has to answer two separate questions:
- Identity: Is this material the compound the label names?
- Purity: Of the components the method detects, what share is that compound?
A record can answer one of these well and leave the other open. That's easy to miss, because a percentage tends to catch the eye.
But a result figure describes how much of something is present, not what that something is. If identity was never confirmed, a high result figure means nothing on its own. Treating the two fields as one number is where reading a COA goes wrong.
Identity: what the material is
The identity result is the COA's answer to a plain question: is this the compound named on the label?
On a well-made record, identity has its own section. It's usually tied to a lab method that can tell one compound from another. The result is typically given as a confirmation (the identity check is consistent with the stated compound), not as a percentage.
So identity is a yes-or-no kind of answer, not a measurement of amount. It says whether this is, or is not, the material the label claims.
That difference matters. The result figure only means something once identity is established, because the figure is measured against an identified compound.
Purity: what the result figure covers, and what it leaves out
The purity figure (sometimes called the main result) is the part of the COA that measures an amount. It answers this question: of the material analyzed, what share is the stated compound? It's reported as a percentage that comes from a lab method.
On peptide COAs, this figure often comes from a method such as HPLC. What HPLC and Mass Spec Mean on a COA explains that method in more detail.
Put simply, the percentage compares the target compound with the related substances the method can detect, under that method's conditions.
There are also a few things it doesn't tell you:
- It doesn't confirm identity on its own.
- It doesn't cover every possible substance other than the target. It only covers what the chosen method can separate and detect.
- It isn't a statement about quality, safety, or whether the material is fit for any purpose. It's a record of a measurement, nothing more.
A result figure always depends on the method used. Without the method behind it, a percentage is an incomplete figure.
Net peptide content vs. the result figure (a common mix-up)
People often confuse the result figure with net peptide content. That's understandable, since both sound like they describe how much peptide is there. They actually measure different things.
| Figure | What it describes |
|---|---|
| Result figure (purity) | The share of the analyzed material that is the target compound, compared with related substances the method detects |
| Net peptide content | How much of the total mass in the container is actual peptide, rather than other mass such as water, counter-ions or leftover salts |
So a record can show a high result figure and a lower net content, and both can be correct. They answer different questions. One is about the makeup of the peptide portion. The other is about how much of the mass in the container is peptide at all.
Where a COA lists both, read them side by side. Neither one tells the whole story alone.
It also helps to look closely at how a record labels these figures. The BPC-157 record, for example, lists a net content of 11.91 mg for the tested sample; the record doesn't say how that figure was determined, so read it as the laboratory's stated quantity rather than as a net peptide content result.
Why one without the other falls short
A complete record needs identity and a result figure. Each one covers a gap the other leaves open.
- Identity without a result figure tells you the material is the right compound, but not how much of it is that compound.
- A result figure without identity gives you a precise measurement of a substance that hasn't been confirmed. It's a number attached to a question mark.
Together, the two describe the material fully: what it is, and how much of it is that thing.
When a record is missing one of them, it isn't just less detailed. It's missing a basic piece, and any conclusion drawn from it carries the same gap.
Reading both on a real record
Here are the published fields for this lot: BPC-157, lot PL-BPC10-0826-01, net content 11.91 mg, published test result 99.62%, test date September 2, 2026, certificate ID POLA2608310062, tested by Freedom Diagnostics.
Purity and identity are still two separate questions here, and it helps to read them together:
- The published test result of 99.62% answers how much. It's the figure the laboratory reported for this lot. The on-page summary doesn't name the method, so the laboratory's full report is where to check what it measures.
- Identity answers what the material is. When a record includes identity testing, that result is what shows the material is the compound named on the label. And identity confirmation, when published, helps confirm that the result figure is describing the right compound in the first place.
The published BPC-157 summary shows the test result, but not a separate identity line. So this worked example is limited to the published fields above.
The laboratory's full report, reached through the Verification Center, is where the identity test and the method behind the figure are listed. A result figure on its own is an incomplete picture. It tells you how much, while a complete record also answers what, through an identity result where one is reported.
Neither figure is a claim about quality, safety, or whether the material is fit for any purpose. Both simply record measurements made on one specific lot.
The limits of a purity number on its own
This part can be confusing, because one tall peak on an HPLC trace looks like a clear answer. But a single large peak doesn't, by itself, show that the peak is the intended peptide. Confirming that takes an identity method, such as mass spectrometry.
EU regulator guidance (EMA, 2025) recommends at least two independent identity methods for synthetic peptides. So a purity figure with no identity result, no lot number and no method behind it tells you very little.
Sources
- Journal articleHoofnagle AN, et al. Recommendations for the generation, quantification, storage, and handling of peptides used for mass spectrometry-based assays
- EMA guidelineGuideline on the Development and Manufacture of Synthetic Peptides
- ICH guidelineICH Q6B Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products
We cite these sources for the general ideas behind identity and purity. They aren't evidence about any PolarLabs material, and citing drug-quality guidance doesn't mean our products are made under it.