How to Read a Peptide Certificate of Analysis (COA)
A certificate of analysis is how you check what you actually received instead of taking a supplier’s word for it. This guide walks through every part of a peptide COA — purity, identity, the chromatogram, accreditation — plus the red flags of a fake, and how to verify a batch for yourself. Written for research-use buyers; nothing here concerns human use.
What a peptide COA is
What is a peptide certificate of analysis? A COA is the analytical record for a specific production batch. It states what the material is (identity), how pure it is (purity), and the lot number that ties those results to the vials produced from that batch. Every research batch should have one.
The document is only as strong as who issued it. An independent, accredited laboratory — ideally one operating to ISO/IEC 17025 — carries more weight than an unverifiable in-house claim, because the lab’s competence and methods have themselves been assessed. A COA is a batch-level document: it describes the batch your vial came from, not peptides in general.
The parts of a COA — a section-by-section walkthrough
A complete peptide COA has a handful of distinct sections. Read them together — no single number tells the whole story.
Product name, lot/batch number and dates
The top of the certificate should name the product, give a unique lot or batch number, and show the dates the sample was received and reported. The lot number is the thread that connects the paper to the physical vial in your hand — without it, a COA can’t be matched to anything.
HPLC purity (%) — what “≥98%” means
High-performance liquid chromatography separates the components of a sample and measures each as a fraction of the total. A purity of “≥98%” means the main component accounts for at least 98% of the integrated UV peak area at the stated wavelength. Note what this is and isn’t: the percentage is an assertion; the chromatogram behind it is the evidence. A number with no chromatogram is a claim you can’t check.
Mass spectrometry identity — observed vs theoretical mass
Mass spectrometry (MS) confirms the sample is the right peptide by comparing the observed molecular weight against the theoretical weight calculated from the sequence. HPLC purity alone cannot do this — a sample can be 99% pure and still be 99% the wrong molecule. A trustworthy COA reports the observed mass and shows it matching the expected value within the tolerance appropriate for the peptide’s size.
The chromatogram
The chromatogram is the graph of the HPLC run. What you want to see is a single dominant peak sitting on a low, flat baseline. Multiple peaks, or a large secondary peak next to the main one, indicate impurities or related substances. The shape of the trace tells you more than the headline percentage does.
Lab name and accreditation
Look for the testing laboratory’s name and any accreditation. A third-party result outranks an in-house one, and ISO/IEC 17025 accreditation is a strong signal that the lab’s methods and competence have been independently assessed. “Tested” with no lab named is not verifiable.
How to verify peptide purity
How do you verify peptide purity? With two pillars, read together: HPLC purity (how much of the sample is the main component) and MS identity (that the main component is the correct molecule). One without the other is incomplete — high purity of an unconfirmed compound, or a confirmed identity with no purity figure, each leaves a gap. A complete picture needs both, plus the chromatogram as the underlying evidence.
Red flags of a fake or incomplete COA
How do you spot a fake peptide COA? Watch for any of these:
- No chromatogram image — only a stated percentage with nothing to back it.
- MS section shows only the theoretical mass, never an observed one (identity was never actually measured).
- An implausibly tight mass tolerance (e.g. ±0.1%) quoted on a large peptide.
- Missing lot or batch number — the certificate can’t be tied to any specific vial.
- No testing laboratory named, or an unverifiable one.
- No received/reported dates.
- Purity reported but identity never confirmed.
A minimum COA checklist
At a glance, a usable COA should include:
- Accession / sample number
- Product name and lot/batch number
- Received and reported dates
- Identity confirmation (mass spectrometry)
- Purity (%) with supporting chromatogram
- Testing laboratory name (ideally accredited)
How to verify a Cellworks batch
Every Cellworks vial is labelled with a lot number in the format CW-YYYY-NNN and a QR code. Scan the QR, or enter the lot number on our verify tool, and you’ll see the Certificate of Analysis for that exact batch — the identity and measured purity for the vial in your hand, not a generic sample. It’s the self-serve version of everything above. For the reasoning behind our documentation, see our quality standards; for an example, look up the batch on any product page such as BPC-157. Everything we test is supplied for research use only.
Verify a batch
Every order ships with a per-batch Certificate of Analysis. Have a vial in hand? Enter its lot number to look up the COA for that exact batch.
FAQ
What purity should a research peptide be?
Does HPLC prove identity?
What is a chromatogram?
How do I check a Cellworks COA?
What is ISO 17025?
RESEARCH USE ONLY — NOT FOR HUMAN CONSUMPTION. All products are sold strictly for in-vitro laboratory research and are not intended for human or veterinary use, ingestion, or administration. Nothing on this page is a medical or efficacy claim. You must be 21 or older to browse this catalog.