How to Read a Peptide Certificate of Analysis (CoA)
A Certificate of Analysis is only as useful as the reader's ability to check it. Most buyers see a percentage next to the word "purity" and stop reading. The document usually contains four or five separate measurements, each answering a different question, and a batch number that either matches the vial in hand or does not.
What a CoA actually is
A Certificate of Analysis is a lab report tied to one specific production batch, not to a compound in general. A supplier can hold a valid CoA for one batch of a peptide while shipping a different, untested batch of the same compound. That distinction, batch-specific versus compound-general, is the single most important thing to check before trusting any purity number.
Independent testing means the laboratory issuing the report is not the same organization that manufactured the compound. This matters because a manufacturer grading its own output has an inherent conflict of interest; an independent lab has no stake in the result. As we outline on our Science page, this is why Helix works with a third-party laboratory (Janoshik) for its tested SKUs rather than publishing internal manufacturing figures as if they were verification.
The purity figure: what HPLC actually measures
High-Performance Liquid Chromatography separates a dissolved sample into its component molecules and measures the relative amount of each. The purity percentage on a CoA is the area of the target compound's peak divided by the total peak area across the chromatogram, expressed as a percentage. A result of 99% means the target peptide accounted for 99% of everything detected; the remaining 1% is typically synthesis-related impurities such as truncated or deletion sequences that share most of the target's structure (USP General Chapter <621>, Chromatography).
Purity is not the same measurement as concentration. Purity describes what fraction of the powder is the target compound. Concentration describes how much of that compound is actually in the vial. A CoA can report high purity on a sample that still under-delivers on labeled dose if the fill weight was inaccurate, which is why some CoAs report both figures separately.
Identity confirmation: the second, separate check
Purity alone does not confirm that the compound is what the label claims. Mass spectrometry answers that question by measuring the molecule's mass-to-charge ratio and comparing the result against the theoretical molecular weight of the intended sequence (International Council for Harmonisation, ICH Q6B, Specifications for Biotechnological Products). A CoA that reports purity without any identity confirmation has only answered half the question: how clean the sample is, not whether it is the right molecule at all.
What else can appear on a full-panel CoA
Depending on the format and the testing package ordered, a more complete CoA may also include endotoxin testing (relevant for injectable formats, since bacterial endotoxins can trigger an immune response even in trace amounts), sterility testing (checks for live microbial contamination), and heavy metal screening (arsenic, cadmium, lead, mercury). Not every CoA includes every panel; a report limited to HPLC purity and mass spectrometry identity is common and is not, by itself, a red flag.
Checking that a CoA actually matches what you received
Three checks separate a verifiable CoA from a decorative one:
- The batch number printed on the vial or pen label should match the batch number on the CoA exactly. A CoA with no batch number, or a generic one reused across multiple listings, cannot be tied to the specific unit purchased.
- The report should be hosted or verifiable on the testing laboratory's own platform, not only reproduced as an image or PDF on the seller's site, where it could have been edited.
- The testing date should be recent relative to the batch's production and reasonable shelf life, not years old relative to a current listing.
Helix publishes two SKUs with a batch-tied CoA hosted directly on Janoshik's verification platform: BPC-157 10mg Pen and Retatrutide 15mg Pen. Every other compound in the catalog is manufactured to the same research-grade specification and is described that way, without any mention of testing or a report, third-party or otherwise.
Bottom line
A purity percentage without a batch number is a claim, not a verification. A genuine CoA is dated, tied to a specific batch, issued by a lab independent of the manufacturer, and checkable against the actual unit in hand. Reading past the headline number to those four details is what separates a documented compound from a marketed one.
For a fuller walkthrough of how Helix sources, manufactures, and documents its research compounds, see our Science page.
Frequently asked questions
What does "99% purity" mean on a peptide CoA?
It means the target compound accounted for 99% of the total peak area when the batch was analyzed by HPLC. The remaining 1% is typically synthesis-related impurities, not a measure of concentration or dose accuracy.
Is purity the same as identity confirmation?
No. Purity (via HPLC) measures how clean the sample is. Identity (via mass spectrometry) confirms it is the intended molecule at all. A complete CoA reports both separately.
How do I know a CoA belongs to the batch I actually received?
Check that the batch number on the CoA matches the batch number printed on the product label exactly, and that the report is verifiable on the testing lab's own platform rather than only an image supplied by the seller.
Why do some peptides have a CoA and others don't?
Independent, batch-tied testing has a real cost per batch and is typically applied selectively rather than across an entire catalog. A supplier being specific about which SKUs are tested, rather than applying one purity claim to everything, is a more reliable signal than a blanket claim.
For research use only. Not for human or veterinary use. This article describes how to evaluate laboratory documentation; it does not describe or endorse any use of research compounds outside of qualified laboratory research settings.
Sources
- United States Pharmacopeia. General Chapter <621>, Chromatography. USP-NF.
- International Council for Harmonisation. ICH Q6B, Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products.