What Peptide Purity Means on a COA
Last updated: August 2026 · Research-use information only
How purity is expressed
On most peptide COAs, purity is reported as a percentage derived from a chromatographic method such as HPLC. The figure generally represents the area of the main peak as a proportion of all detected peaks. A higher percentage indicates that fewer other detectable substances were present in the tested sample.
Purity is not the same as amount
Purity and amount answer different questions. Purity asks “of what was detected, how much is the target compound?” Amount (or content) asks “how much target compound is actually in the vial compared to the label?” A sample can be high in purity but low in amount, or vice versa. Reviewing both, where available, gives a fuller picture.
What the method can detect
The reported purity depends on what the method can see. A chromatographic method detects substances that respond under its conditions; it may not capture every possible impurity. That is why some records pair chromatography with additional screens, such as mass spectrometry for identity or separate heavy-metals and sterility testing.
Reading purity claims critically
- Look for the method that produced the number.
- Check whether a chromatogram supports the figure.
- Confirm the batch number and date tie the result to a specific run.
- Be cautious of round-number claims with no supporting data.
Purity does not describe use
A purity value is an analytical measurement. It does not indicate that a compound is appropriate for any particular purpose, and it does not describe handling or human use. Push for Peptides presents purity information only where it is publicly listed and only in a research-use context.
Frequently asked questions
What does 99% purity on a COA mean?
It generally means that, of the substances detected by the testing method, about 99% corresponded to the target compound in that specific sample. It does not describe amount, other batches, or suitability for any use.
Is higher purity always better data?
A higher figure is only as reliable as the method and supporting data behind it. A purity number without a stated method, chromatogram, batch, or date is difficult to interpret.
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