For laboratory research use only. This article explains analytical documents and is not medical advice.
Most people glance at a Certificate of Analysis, spot “99%”, and move on. That number on its own tells you very little. A COA earns your trust only when the batch, the test methods and the lab all check out. And a surprising number of the reports passed around online fail at least one of those.
Here’s how to read one properly. We’ll use real numbers so you can follow the math, and finish with the questions worth asking any supplier before you order.
The 60-second check
- Does the lot number on the report match the one on your vial?
- Is there a mass spec result, and does it match the peptide’s molecular weight?
- Is there an actual HPLC chromatogram, not just a purity figure?
- Is the testing lab named, independent, and able to confirm the report ID?
Four yeses means the document is worth reading in detail. Any “no” means you’re looking at marketing, not data.
Start at the top: the header
Before any chemistry, the header tells you whether the report even belongs to your product. Look for the compound name and sequence, a lot or batch number, the test date, and the name of the lab that did the work.
The lot number matters most. Peptides are made in batches, and each batch can differ slightly. A report for lot 2405-A says nothing about lot 2409-C. If the number on the PDF doesn’t match your label, the rest of the page is irrelevant to the vial in your hand.
Reading the HPLC section
HPLC (high-performance liquid chromatography) separates a sample into its parts. The dissolved peptide is pushed through a packed column, and each compound exits at its own time. A UV detector, typically set around 214–220 nm where peptide bonds absorb, draws a peak for each one.
On the chart, time runs left to right and signal strength runs bottom to top. You want one tall, narrow peak that clearly dominates. The little bumps around it are impurities, usually shortened or incomplete sequences left over from synthesis.
A worked example
Below the chart, most labs print a peak table. Purity is simply the main peak’s share of the total area:
Try this yourself on any report. If the peak table doesn’t add up to the purity printed in the summary, ask why. This is exactly how a “BPC-157 HPLC” result is meant to be read.
The number most people misread
HPLC purity only counts what the UV detector sees. It ignores water, salts, and counter-ions such as acetate or TFA that stay bound to the peptide after synthesis. So a vial can be 99% pure and still be only around 70–90% peptide by weight. Labs call that second figure net peptide content.
This has a real effect in the lab. If a 10 mg vial shows 99% purity and 80% net peptide content, you’re working with roughly 7.9 mg of the target peptide, not 10. Concentration math done from the label weight alone will run high. Our reconstitution guide covers the rest of that calculation.
Reading the mass spec section
HPLC tells you how clean the sample is, but not what it is. A perfectly pure batch of the wrong molecule would still show a single neat peak. Mass spectrometry closes that gap by weighing the molecule.
Compare the observed mass on the report with the theoretical mass for the sequence. For small peptides they should agree within about 1 Da when both use the same convention. Don’t be thrown by several peaks on an ESI spectrum. The same molecule often appears more than once carrying different charges, and the lab usually converts these to a single “deconvoluted” value.
| Peptide | Length | Expected mass (approx.) |
|---|---|---|
| KPV | 3 residues (Lys-Pro-Val) | 342.4 g/mol |
| BPC-157 | 15 residues | 1,419.5 g/mol |
| MOTS-c | 16 residues | 2,174.6 g/mol |
Say a “KPV COA” reports an observed mass of 1,419. That isn’t a rounding issue. It’s a different peptide, and no purity figure can rescue the report.
Signs a COA can’t be trusted
- A purity number with no chart. Anyone can type “99.4%”. The chromatogram is the evidence.
- No identity test. Without mass spec, you only know the sample is pure, not what it is.
- One report for everything. The same PDF reused across products, sizes or years.
- An unnamed lab, or the seller testing itself. Independence is the whole point.
- Suspicious formatting. Cropped headers, mismatched fonts, or numbers that look pasted in.
- Too-perfect results. 100.00% purity is a warning sign, not a selling point.
Questions to ask a supplier before you order
A good supplier answers these quickly and without fuss. Hesitation is an answer too.
- Can I see the COA for the exact lot you’ll ship, not a sample report?
- Which lab tested it, and can I verify the report ID with them?
- Do you test both purity (HPLC) and identity (MS) on every batch?
- Do you report net peptide content or endotoxin levels?
- How often are new batches tested, and when was this one done?
How we handle testing at Project Amino
Every batch is sent to an independent lab for HPLC and mass spec analysis before release. Reports are posted on our certificates page as they’re finalized. If you’d like the report for a specific lot you’ve received, contact our team with the lot number and we’ll send it over.
FAQ
Why do two COAs for the same peptide show different purity?
They’re usually from different batches, and small batch-to-batch variation is normal. Labs also use different columns and gradients, so the same sample can read a few tenths of a percent apart. Large gaps are worth questioning.
Is a higher purity number always better?
Up to a point. The difference between 98.5% and 99.2% rarely matters as much as whether identity was confirmed by mass spec. A verified 98.5% beats an unverified 99.9%.
Is a COA from the manufacturer enough?
It’s a start, but an independent third-party report carries more weight because the lab has no stake in the result. Ideally you’d see both.
How long is a COA valid?
A COA describes a batch at the time it was tested. Lyophilized peptides are stable when stored correctly, but a report from years ago tells you little about how a vial has been handled since. Recent testing and proper cold storage go together.
What does “EU/mg” mean on some reports?
It’s the unit for bacterial endotoxin, measured with the LAL test. Not every research COA includes it, but it’s a useful extra when it does.
Check the data yourself
Browse our batch certificates or explore research peptides tested by independent labs.
All Project Amino products are sold strictly for laboratory research. They are not drugs, foods or cosmetics, have not been approved by the FDA, and are not intended to diagnose, treat, cure or prevent any disease. Not for human or veterinary use.
