The journal
How to read a certificate of analysis
A certificate of analysis is the only document standing between a claim and a measurement. It is also, in this industry, the document most often faked, borrowed, or quietly detached from the material it is supposed to describe. Here is what a real one contains, and what each part is actually for.
1. A named laboratory you can look up
The single most important field, and the one most often missing. A certificate should name the laboratory that ran the analysis, and that name should belong to a real analytical chemistry business you can find, telephone, and ask whether they tested a given lot.
“Third-party tested” with no third party named is not a claim about testing. It is a claim about marketing.
2. A lot number that matches your vial
A certificate is evidence about a specific batch of material. The lot number is the only thing tying the document to the glass in your hand. If the number on the certificate appears nowhere on your vial or your packaging, the certificate is evidence about somebody else's material.
This is the check that takes five seconds and is skipped most often. Do it anyway. It is also why the certificates here are searchable by lot rather than filed under a product name — a product name is shared by every batch ever made; a lot number is not.
3. The chromatogram, not just the percentage
High-performance liquid chromatography separates everything in a sample and measures how much of each thing there is. The output is a trace: a large peak where the target compound comes off the column, and smaller peaks wherever anything else did. Purity is the area of the main peak as a fraction of the total.
A typed percentage throws away everything except that one number, and the shape is where the information lives. Two lots can both report 99.1% and look nothing alike:
- One shows a single narrow peak on a flat baseline. That is what you want.
- The other shows the same peak with a shoulder on one side — a closely related impurity co-eluting, so close that the integration has partly counted it as product.
- A third shows a cluster of small peaks near the solvent front that a shallow integration window has quietly excluded from the total altogether.
All three can be made to print 99.1%. Only one of them is a clean lot. Ask for the trace.
4. A mass spectrum with observed versus theoretical mass
HPLC tells you how much of the sample is one substance. It does not tell you which substance. A sample can be 99.8% pure and be 99.8% pure something else.
Mass spectrometry is the identity check. It weighs the molecule, and a certificate should show the observed mass beside the theoretical mass calculated from the molecular formula. Those two figures should agree. Discrepancies are informative rather than merely bad:
- +16 Da is one oxygen — typically an oxidised methionine.
- +18 Da on a cyclic peptide suggests a chain that never closed its ring, since forming the bond expels a molecule of water.
- −71, −97, −113 Da and similar are the residue masses of alanine, proline and leucine or isoleucine — the signature of a deletion sequence, one residue short.
A certificate showing only a purity number and no mass at all has verified homogeneity and nothing else.
5. A date
Peptides degrade. A certificate dated eighteen months before your order raises a fair question about what has happened to the material since, and whether the number still holds. A dated certificate is a measurement with a timestamp; an undated one is an assertion.
What we do with all of this
Every lot is tested by an independent third-party laboratory before it reaches us, then tested again in our own laboratory when it arrives, and only then does it ship. The order is deliberate. A supplier that tests its own material first and sends it out for confirmation afterwards has already decided what the answer should be.
The certificate filed against your order belongs to the vials you were sent. You can find it by lot number in the COA lookup, and the method behind it is set out on the quality page.
All products supplied by Alpha Aminos are for laboratory research use only and are not for human or animal consumption. Nothing on this page describes or is intended to describe an effect of any compound. No statement here has been evaluated by the Food and Drug Administration, and nothing here is intended to diagnose, treat, cure, or prevent any disease.