The sheetThe four lines that matter
Read them in this order. A sheet missing any of them isn't a certificate — it's a highlight reel.
Identity
Usually mass spec. Is this the compound on the label at all? Purity without identity is just a percentage of a mystery.
Purity
Usually HPLC. Of the material that's there, how much is the target versus related impurities? 99% pure of the wrong molecule is still the wrong molecule.
Net content
How much is actually in the vial versus what the label claims. A spotless 99% vial that's 30% short is still 30% short.
Endotoxin
The bacterial-breakdown load sterile filtration is meant to catch. For anything headed into a research model, it's the one you don't skip.
ProcessOne sheet, two stages
Done right, identity / purity / net content / endotoxin run on the raw material, then identity / purity / net content again on the finished vial.
Two stages — because a clean input can still fail on the way out. If a certificate only shows one stage, you're seeing half the story: the material may have tested clean in bulk and still drifted during fill and finish.
DiligenceRed flags vs green flags
- A batch-specific lot number that matches the vial in your hand
- Identity by mass spec and purity by HPLC, with the chromatogram shown
- Net content and endotoxin both reported
- A test date and a signature
- A way for you to verify it yourself
- No lot number, or a generic PDF that could front any batch
- A purity number and nothing else — no identity method
- No endotoxin line at all
- A file you were emailed that you can't tie to your vial
- "Trust us" instead of "here's how to check"
VerificationA COA proves nothing you can't tie to the vial
A PDF is a photograph of a single moment — and on its own, nothing ties it to the vial in your hand. The same file can front a hundred lots, including the ones that were never tested. Reuse costs nothing.
So the question isn't "is there a COA" — it's "can I verify this lot's COA, myself, right now." The gap between those two questions is where every bad batch lives. Work out the numbers with the reconstitution & dosing calculator once you trust the material.
GlossaryKey terms, defined
The vocabulary on a peptide COA, in plain English.
- Certificate of Analysis (COA) — a batch-specific document reporting a material's lab test results for one production lot.
- Identity — confirmation that a material is the compound named on the label, usually by mass spectrometry.
- Purity — the proportion of a sample that is the target compound versus related impurities, usually by HPLC.
- HPLC — High-Performance Liquid Chromatography; the standard method for measuring target versus impurities.
- Mass spectrometry — an analytical method that measures a molecule's mass to confirm its identity.
- Net content — how much material is actually in the vial, compared with the label's claim.
- Endotoxin — bacterial-breakdown residue that sterile filtration is meant to remove; measured because it can confound a result.
- LAL test — Limulus Amebocyte Lysate assay; the standard test for measuring endotoxin.
- Lot / batch number — a code identifying one production run, used to tie a certificate to the exact vial.
- Lyophilized — freeze-dried into a stable powder; how most research peptides ship before reconstitution.
- Reconstitution — dissolving a lyophilized peptide in a diluent (usually bacteriostatic water) to make a usable solution.
Research-grade peptides, third-party tested
Every batch ships with a Certificate of Analysis you can verify — the whole point of this guide.
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