1.
Purity
Proportion of target peptide vs impurities, by area under the curve
Quality & documentation
How to Read a Peptide COA
What each field on a peptide Certificate of Analysis means, and how to check one against the vial it describes.
Written and reviewed by Peptide.Express Editorial TeamLast reviewed
Quick Answer
Start with the lot or batch number on the vial label. If it does not match the CoA, stop — the rest of the document does not describe that vial. Then read HPLC purity with the chromatogram, LC-MS/MS mass vs theoretical weight, appearance, endotoxin if reported, test date, and the named lab. A CoA is a batch record, not a product brochure. For laboratory research use only. Not for human or veterinary use.
2.
Identity
Molecular weight matches the published value for the compound
3.
Batch certificate
The number printed on your vial label should appear on the certificate verbatim. Match the compound and lot to the original report.
HPLC Sourcing Specification
Lots are sourced against a ≥99% HPLC purchasing specification. Measured purity is the HPLC area-percent recorded on that lot's Certificate of Analysis. Certificates of Analysis are published where documents are on file, including lot-specific, historical and product-level records.
Endotoxin and sterility lines
When a laboratory reports them, a Certificate of Analysis can include an LAL (Limulus Amebocyte Lysate) endotoxin result and microbial screening. Endotoxin is heat-stable and survives sterile filtration, so a sterility result does not imply an endotoxin result. A missing line is not evidence the test was never run, and it is not a pass.
What we can show you the numbers for
- 25 Certificates of Analysis published.Verify with the issuing laboratory: BPC-157 · CJC-1295 + Ipamorelin (No DAC) · Epithalon · GHK-Cu · HCG · HGH · Ipamorelin · Kisspeptin-10 · KLOW Blend · KPV · Melanotan II · Mitochondrial Fuel Stack · MOTS-c · NAD+ · PT-141 · Retatrutide · Retatrutide Pen · Semax · Semax Nasal Spray · Sermorelin · SS-31 · TB-500 · Tesamorelin · Tirzepatide · Wolverine Blend.
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Testing Methodology
A complete batch record can include the checks below. Each answers a different question, and none of them substitutes for another. The page shows the results the laboratory reported for that lot. A purchasing specification is not a measured result, and a missing line is not proof a test never happened.
| Test | Method | What It Confirms | How to Read It |
|---|---|---|---|
| Purity | HPLC (reverse-phase C18) | Proportion of target peptide vs impurities, by area under the curve | ≥99% sourcing specification |
| Identity | LC-MS/MS | Molecular weight matches the published value for the compound | Theoretical mass, where reported |
| Endotoxin | LAL (Limulus Amebocyte Lysate) | Gram-negative bacterial endotoxin content | Where the laboratory reports it |
| Appearance | Visual QC | Physical form, colour, particulate matter | Where recorded: white to off-white powder (GHK-Cu and blends are deep blue) |
| Solubility | Reconstitution test | Complete dissolution in standard diluents | Where recorded: full dissolution, no visible cake |
What HPLC Tells You — And What It Doesn't
Reverse-phase HPLC separates a peptide sample by hydrophobicity. The sample is driven through a C18 column under pressure with a water/acetonitrile gradient, and a detector records absorbance as each species elutes. The output is a chromatogram: peaks against a time axis. Purity is the area of the target peak divided by the total area of every peak on the trace, expressed as a percentage.
That definition carries two limits worth stating plainly.
HPLC does not identify the impurities. A batch reported at ≥99% has a remaining fraction of under 1%, and the chromatogram says nothing about what is in it. Truncated sequences from incomplete coupling steps, deletion sequences missing a residue, residual trifluoroacetate from purification, solvent traces — these all appear as small peaks with retention times, not as identified compounds. Characterising them takes a separate analysis.
HPLC does not confirm the main peak is the right molecule. A chromatogram showing a single sharp peak at 99.4% is evidence of a clean, homogeneous sample. It is not evidence that the sample is the peptide named on the label. Retention time is characteristic but not diagnostic — two peptides of similar hydrophobicity can co-elute or elute within seconds of each other. Purity by HPLC is a statement about homogeneity. Nothing more.
An HPLC percentage on its own reports one of the two properties; identity needs a separate measurement. Peptide characterisation practice, and the reason mass spectrometry is run alongside chromatography rather than instead of it, is documented across the analytical literature: FDA guidance: Analytical Procedures and Methods Validation for Drugs and Biologics.
What LC-MS/MS Adds
Liquid chromatography coupled to tandem mass spectrometry closes the gap HPLC leaves open. The chromatography stage separates the sample; the mass spectrometer then measures the mass-to-charge ratio of what elutes and compares it against the theoretical molecular weight for the named compound. Purity says how much. Mass says what.
TB-500 is the clearest illustration of why this matters. The name is applied across the research market to at least two different molecules. One is full-length synthetic Thymosin β-4, a 43-residue peptide with a molecular weight of 4,963.4 Da. The other is a short fragment built around the LKKTET actin-binding motif, weighing in around 890 Da depending on the exact fragment and any N-terminal acetylation. Both ship under the label "TB-500". They are not the same compound, they do not behave the same way in an assay, and a researcher who assumes one and receives the other has a protocol built on the wrong molecule.
No purity figure distinguishes them. Both can be 99% pure. The mass on the Certificate of Analysis is the only reliable way to know which one is in the vial — roughly 4,963 Da or roughly 890 Da, and the difference is not subtle. Read the mass field before you read the purity field.
Third-Party Testing
A laboratory that tests material it produced has an interest in the outcome. That is not an accusation of misconduct — it is a structural problem with self-verification that exists regardless of anyone's intentions. When the party running the assay is the party that loses money if the assay fails, the result is not an independent check.
Where a certificate is on file, the laboratory named on it is a separate business from Peptide.Express. The document names that facility, and the lot or accession it prints.
Peptide.Express does not conduct in-house purity testing. Purity and identity figures published from a certificate come from the independent laboratory named on that certificate. A supplier certificate is a starting point for reading a lot, not a measured result by itself. Batch certificates are published in the lab results library where documents are on file.
How to Read Your Certificate of Analysis
Each field answers something specific, and the fields are not interchangeable in importance. Start with the lot number and work down.
1.
Compound name
The full chemical or accepted scientific name, not the marketing name. If your vial says "Wolverine Blend" and the CoA says "BPC-157" and "TB-500" as separate line items, that is correct — the document reports on the molecules, not the SKU.
2.
Batch / lot number
The single most important field. It ties this document to one specific synthesis run. The number printed on your vial label should appear here verbatim.
3.
HPLC purity result and chromatogram
A percentage plus the trace it was calculated from. The chromatogram matters as much as the number: you are looking for one dominant peak with a clean baseline, not a headline figure sitting on its own.
4.
LC-MS/MS mass data
The observed molecular weight against the theoretical value for the named compound. Agreement here is what turns a purity figure into a purity figure for the right molecule.
5.
Appearance
Physical form and colour as observed at QC. White to off-white lyophilized cake for most compounds. GHK-Cu is the exception — the copper complex is deep blue, as are blends containing it such as KLOW, and a pale or colourless GHK-Cu solution is the abnormal result.
6.
Endotoxin result
When the laboratory reports an LAL result, it is the endotoxin figure for that batch, in endotoxin units. A missing line is not a pass, and it is not proof the assay never ran. The figure matters in cell-culture work, where endotoxin at low concentrations shifts cytokine readouts.
7.
Test date
When the analysis was run. A CoA dated well before the synthesis date on the vial is a document that belongs to a different lot.
8.
Testing laboratory
The named facility that performed the analysis. On Peptide.Express certificates this is a third-party laboratory, not Peptide.Express. Verify the certificate against the issuing laboratory's own records.
One CoA, one batch. Certificates are not shared across a product line. Reorder the same compound three months later and it will very likely come from a different synthesis run with its own document and its own numbers. The lot number on the vial maps to exactly one record — that mapping is the whole point of the system. Reconstitution handling for the compound you received is covered in the peptide reconstitution protocol guide, and the hazard classification, personal protective equipment, storage incompatibilities and disposal route for it are in that compound’s Safety Data Sheet.
Walkthrough: reading a real Peptide.Express CoA
The example is the Ipamorelin 10mg certificate listed in the lab results library. Each value below is read from that card and its public certificate record, in the order the Quick Answer gives.
1. Lot
The certificate prints lot PXIPA10829. Compare it with the lot on the vial label. If the two differ, this certificate does not describe that vial.
2. Purity and method
Purity is 99.27% by HPLC. That is the area-percent of the main peak: how much of the sample is one species, not which species it is.
3. Mass confirmation
The public record marks identity (LC-MS mass) as not recorded. A missing line is not a pass. Look for an observed-versus-theoretical mass line on the certificate itself; if it has none, the certificate does not confirm identity by mass.
4. Laboratory and accession
The issuing laboratory is Mistral Diagnostics. The accession number on the lab results card is 62503: the laboratory's own identifier for this analysis, separate from the lot. No test date is recorded.
5. Other lines
The record also lists endotoxin: pass (LAL) and heavy metals: pass, as reported by the laboratory.
6. Verify with the laboratory
Open the laboratory's verification page on mistraldiagnostics.com for accession 62503 and check that the compound, lot and figures match the copy published here.
Quality & Purity Testing FAQ
What if the lot number on my vial doesn’t match the CoA?
Then the CoA does not describe that vial, and its results do not apply to the material in it. Do not use the material for research until the mismatch is resolved. Email info@peptide.express with the lot number printed on the vial label, and Peptide.Express will check which certificate, if any, is on record for that lot. A certificate for a different lot, or a product-level PDF, is not a substitute. Research use only.
What is the difference between a lot number and a lab accession number?
A lot or batch number is the supplier’s identifier for one synthesis and release run. It must match the number printed on the vial. A lab accession or report number is the testing laboratory’s own identifier for that analysis job. Both can appear on a complete certificate. Matching the vial to the CoA uses the lot number. Authenticating the document at the laboratory, when the lab offers a lookup, uses the lab’s report or accession identifier, not the product SKU. Research use only.
How do I verify a CoA with the laboratory that issued it?
A certificate published on a seller’s site, including this one, is a copy hosted by the seller. To verify it, retrieve the same report from the issuing laboratory: through the laboratory’s portal, a QR code on the document, or a lookup by report or accession number. Then check that the compound, lot and figures on the laboratory’s copy match the published copy. Research use only.
What if the Lot field on a CoA says N/A?
Then the certificate prints no lot, so there is no lot to match and none should be assumed. Match the document by its accession number in the laboratory’s portal, or retrieve the certificate that belongs to the vial you hold. A product-level PDF is not a substitute for a lot match. Research use only.
Original documentation
Open the certificate index to review available batch records. Peptide.Express does not perform in-house purity testing.
Research Use Disclaimer
All products listed on Peptide.Express are supplied for in-vitro laboratory research and educational purposes only. Nothing on this page is medical advice, and no compound described here is intended for human consumption, clinical use, or veterinary use.
Endotoxin methodology background: USP General Chapter <85> Bacterial Endotoxins Test.