A COA can look like one verdict on the page, but it’s really answering two questions. What is this material? And how much of it is the stated compound? Those two are identity and purity — and mixing them up is one of the most common mistakes when reading a record. This guide explains what each one means, and why a complete record needs both. New to the format? Start with How to Read a Peptide COA.
Two different questions a COA answers
Think of a COA as a document that has to satisfy two independent claims before it is complete:
- Identity: Is this material the compound the label names?
- Purity: Of the material present, what fraction is that compound?
A record can answer one question well and leave the other unaddressed. A high result figure means nothing if the identity was never confirmed, because a result figure describes how much of something is present, not what that something is. Reading the two fields as one number is where interpretation goes wrong.
Identity: confirming the compound is what the label says
The identity result is the COA’s answer to “is this the compound named on the label?” On a well-formed record you will find a dedicated identity section, usually tied to an analytical method that can distinguish one compound from another. The result is typically reported as a confirmation — the identity check is consistent with the stated compound — rather than as a percentage.
Where the COA lists the identity result, it is making a categorical statement, not a quantitative one. It is not saying “99 percent”; it is saying “this is, or is not, the material the label claims.” That distinction matters because everything the result figure tells you is only meaningful once identity is established. A result figure is measured against an identified compound.
Purity: what the result figure does and does not include
The purity or main-result figure is the quantitative attribute. It answers “of the material analyzed, what proportion is the stated compound?” and is reported as a percentage derived from an analytical method. On peptide COAs this figure is often produced by a method such as HPLC — covered in detail in What HPLC and Mass Spec Mean on a COA.
What a result percentage does: it expresses how much of the analyzed material corresponds to the target compound relative to detectable related substances, under that method’s conditions.
What it does not do:
- It does not, on its own, confirm identity.
- It does not describe every possible non-target substance — only what the chosen method can separate and detect.
- It is not a statement about quality, safety, or suitability for any purpose. It is a documentation attribute describing a measurement, nothing more.
A result figure is always method-dependent. A percentage read without the method behind it is an incomplete figure.
Net peptide content vs. the result figure (a common mix-up)
The result figure and net peptide content are frequently conflated, but they measure different things.
| Attribute | What it describes |
|---|---|
| Result figure (purity) | The proportion of the analyzed material that is the target compound, relative to related substances the method detects |
| Net peptide content | How much of the total mass in the container is actual peptide, versus other associated mass such as water, counter-ions, or residual salts |
A record can report a high result figure and a lower net content, and both can be correct — they are answering different questions. One is about the composition of the peptide fraction; the other is about how much of the vial’s mass is peptide at all. On the BPC-157 record, for example, the net content is stated as 11.91 mg. Where a COA lists both, read them side by side rather than treating either as the whole story.
Why both must be present for a record to be complete
A complete record needs identity and a result figure because each 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 an unconfirmed substance — a number attached to a question mark.
Only together do the two attributes describe the material fully: what it is, and how much of it is that thing. When a record is missing one, it is not simply less detailed — it is structurally incomplete, and any conclusion drawn from it inherits that gap.
Reading identity and the result together on a real record
For this lot, the verified public fields are: 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. The published test result answers how much — it is the batch-specific result figure the laboratory reported.
Purity and identity remain two separate questions, read together:
- The published test result of 99.62% speaks to how much of the analyzed material is the stated compound, as reported for this lot.
- Identity answers what the material is. When a record includes identity testing, that result is what establishes the material is the compound named on the label; identity confirmation, when published, helps confirm the result figure is describing the right compound in the first place.
The published BPC-157 record shows the test result but does not display a separate identity line, so the worked example is limited to the verified fields above — any identity result, or the analytical method behind the 99.62% figure, should be added only once it is confirmed on the certificate itself. 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 suitability — both are documentation attributes describing measurements on a specific lot.