Explainer
How to read a peptide COA
What each line on a certificate measures, which tests appear by default, which are usually missing, and the two numbers people merge into one.
Read the explainerCertificates
Reading a certificate of analysis
Two pages sit here, and between them they answer one question: what has a certificate of analysis actually established. A certificate is a strong document within its own boundaries and a silent one outside them, and almost every argument about one comes from reading a number on it as an answer to a question it was never asked. These pages set out what is measured, what is inferred, and what is missing.
Short answer
What this section is: two pages on the document that arrives with a batch: what it reports, what each line measures, and the far longer list of things it does not cover.
What a certificate is: the results of named tests, run by named methods, against named acceptance criteria, for one batch. It records what was measured, and measurement is the whole of its authority.
The number everyone reads first: the HPLC purity percent, which is an area share of what eluted and was detected. It is not identity, not sequence, not sterility, and not how much peptide is in the vial.
Why the absences matter: sterility, bacterial endotoxin, elemental impurities and residual solvents each have their own compendial test and their own sample. A certificate that does not list them has not passed them, it has not run them.
On this page
What can a certificate actually prove?
That the tests it lists were run, by the methods it names, and returned the results it prints, for the one batch it identifies. That is a real claim, and it is a narrow one.
What it cannot reach: anything outside the sample tested. A certificate says nothing about a different batch, nothing about how the material was stored afterwards, and nothing about whether the vial in hand is the vial the document describes.
Which is why the header lines matter: the batch identifier, the test dates and the method names are the part that makes the numbers checkable. A certificate without them is a claim in the shape of a document.
Why is purity not the same as content?
Because they answer different questions and are produced by different tests, and merging them is the most common misreading of the whole document.
Purity is a share: the main peak expressed as a percentage of the total detected peak area. It describes the composition of what was detected, not the quantity of anything.
Peptide content is a quantity: how much of the powder in the vial is actually peptide, with the remainder being water and counterion. A batch can report a high purity figure and still contain less peptide than a label implies, and the two figures never substitute for one another.
How do the two pages relate?
One reads the whole document: the certificate page walks the lines that usually appear, appearance, identity by mass spectrometry, purity by reversed-phase chromatography, water and counterion content, and names what each one establishes.
The other takes one number apart: the purity page goes after the single most-quoted figure on any certificate, including the reporting threshold beneath which peaks are simply not counted.
Read together: the first tells you what a certificate covers, and the second tells you how much weight its headline number can carry. Neither is a verdict on any particular vial.
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The two pages
Both work from the compendial definitions: what a named test measures, and what it is defined to exclude.
Explainer
What an HPLC purity number does not cover
An area percent of what eluted and was detected, the reporting threshold beneath it, and everything the detector never sees.
Read the explainerThe disclaimer
Every page is reviewed by medical professionals before it ships, and written with longtime biohackers who were doing this before it was a trend. Reviewed still does not mean prescribed: nothing here is medical advice. It is research, trial data, and reported use, with the numbers intact so you can check them. For decisions about your body, see a doctor who can look at your labs.
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