A certificate of analysis is only useful if you can tell which parts of it are evidence and which parts are decoration. Here is what each field means and what it does not.
Most people never read the certificate of analysis. They see that one exists, take that as the answer, and move on. That is reasonable, because the document is written for analysts rather than for buyers, and almost nothing on it explains itself.
It is worth learning to read anyway. A certificate is the only part of a research peptide purchase that can be independently checked. Everything else is a claim.
A certificate of analysis records what a laboratory measured when it tested a specific batch of material. It is not a guarantee about a product line, and it is not a statement about the compound in general. It describes one batch, on one date, by one method.
That scope matters more than anything else on the page. A certificate from a batch produced eighteen months ago says nothing about the batch you are being sent. This is the single most common way certificates get used to imply something they do not support.
Lot or batch identifier. This is the field that makes the rest of the document meaningful. It should appear on the certificate and on the physical item, and the two should match. Without it you have a laboratory report about an unspecified quantity of material somewhere in the world.
Test date. Tells you how old the analysis is, and whether it precedes or follows the production of the batch you hold.
Analytical method. Usually high performance liquid chromatography for purity, and mass spectrometry for identity. The method should be named. A purity figure with no stated method is a number without units.
Purity. Typically expressed as a percentage of total peak area from the chromatogram. This is the number everyone quotes and the number most often misread. See below.
Identity confirmation. Mass spectrometry compares the observed molecular mass against the expected mass for the sequence. This answers a different question from purity: it asks whether the material is the compound it claims to be at all, rather than how much of it is that compound.
Laboratory identification. A name, and ideally contact details. A certificate you cannot trace back to a laboratory that will confirm it is a design element.
This is the distinction worth carrying away.
Purity answers: of the peptide-related material present, what fraction is the target compound? A 99% purity result means that in the chromatogram, 99% of the total peak area belongs to the peak of interest and 1% is distributed across other peaks.
Content, sometimes called potency or assay, answers: how much target compound is physically present in this container?
These come apart constantly. Lyophilised peptide is mixed with residual water, counterions and salts left over from synthesis and purification. None of that shows up as an impurity peak, because it is not peptide. So a vial can report excellent purity while containing meaningfully less peptide than the label claims, and the certificate is not lying. It is answering the question it was asked.
If a certificate reports only purity, it has told you the material is clean. It has not told you how much of it there is.
The trace is more informative than the summary figure, and it takes about ten seconds to get value from it.
The target compound is the large peak, usually annotated with its retention time. Impurities appear as smaller peaks elsewhere on the baseline. What you are looking for is the shape of the story: one dominant, symmetrical peak with a flat baseline is a clean result. A dominant peak with a cluster of small peaks immediately beside it usually indicates closely related synthesis by-products, such as sequences missing a single residue.
A baseline that wanders, or a peak that trails off asymmetrically on one side, suggests the separation itself was not clean. That does not necessarily mean the material is bad, but it does mean the purity number resting on it deserves less confidence.
A certificate with no batch identifier, no test date, or no laboratory name cannot be connected to anything.
A purity figure quoted without a chromatogram is a claim rather than evidence. The trace is what makes the number checkable.
A certificate for a different batch than the one you are being sent is the most common substitution, and it is easy to miss because the document is otherwise entirely genuine.
An image of a certificate with a resolution too low to read the axis labels is worth treating as absent.
Every ReadyPep lot is tested by an independent laboratory, and the certificate for that specific lot is published rather than summarised. The lot number on the pen matches the lot number on the certificate, which is what makes the document verifiable rather than reassuring.
You can read the certificates without an account and without asking us, because a certificate nobody can open corroborates nothing.
ReadyPep supplies materials for laboratory research use only. Nothing here describes use in humans, and nothing on a certificate of analysis speaks to that question either.