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How to read a certificate of analysis

What a peptide COA shows, how to tell a real one from a template, how to verify it yourself, and what the numbers mean for lab work.

Updated 27 September 2026About 10 minutesApplies to any supplier, including this one
Vendor-agnostic. This page is about documents and analytical methods. Use it on any supplier's certificate. Research chemicals are not medicines and are not for human use; nothing here changes that.
On this page
  1. What a COA is
  2. The fields and what they mean
  3. Real versus template
  4. Red flags on the document
  5. Verify it yourself
  6. What the numbers mean for lab work
  7. How this catalogue handles it
  8. Questions to ask any supplier
  9. Red flags in how a supplier behaves
  10. If the material does not match
  11. The law in Australia, briefly

1. What a COA is

A certificate of analysis is a document issued by a laboratory that reports the tests run on one specific batch of material and their results. A real certificate ties one batch, identified by a batch or lot number that matches the vial label, to named analytical methods, a test date and an identifiable laboratory. It is evidence about that batch. A certificate without a batch number, or one reused across batches, is a claim, not evidence.

2. The fields and what they mean

FieldMethodWhat it tells you
Peptide purityHPLC, main peak area as a percentageThe share of peptide-related material that is the target sequence. Batches in this catalogue are typically 98% or above; the lab results page gives the exact figure per batch.
IdentityMass spectrometry (ESI or MALDI)The observed mass matches the expected mass of the target sequence. Without a spectrum or chromatogram the certificate is text, not a test.
Related substancesHPLC, individual peaksTruncated or modified sequences and synthesis by-products. Individual peaks above about 1% deserve a question.
Water contentKarl Fischer titrationMoisture in the lyophilised powder. It reduces how much of the label weight is peptide and affects storage.
CounterionReported as TFA or acetate, sometimes with a percentageTrifluoroacetate is heavier than acetate and can be a larger share of the weight. Some labs report TFA content directly.
Net peptide contentCalculated from purity, water and counterion, or measured by amino acid analysisThe mass of peptide actually in the vial, which is lower than the label weight. This is the figure to use for concentration arithmetic.
EndotoxinLAL assay, in EU per mgBacterial endotoxin. It matters for cell culture and animal work, where it confounds results.
Batch number and datesPrinted on the certificateThe batch must match the vial. The test date should be recent relative to the batch.
LaboratoryName, address, methods, a verify codeA lab you can find, and ideally a report you can check on the website of the lab itself.

3. Real versus template

Template or unreliable

  • No batch number, or the same number on every shipment
  • A lab name you cannot find anywhere
  • No chromatogram and no mass spectrum, just text
  • Purity written as "100%" or "99.99%"
  • The same test date on several "batches"
  • A phone screenshot rather than a PDF
  • Lab and supplier share an address

Legitimate third-party certificate

  • Batch number matches the label on the vial
  • Named lab with a public website and a verify page
  • Visible HPLC chromatogram and mass spectrum
  • Realistic purity with decimals (98.4%, 99.2%)
  • Dated and signed, within the material's shelf life
  • A PDF with document metadata
  • An independent lab, often in a different country from the supplier

4. Red flags on the document

5. Verify it yourself

6. What the numbers mean for lab work

The label weight is gross. Worked example: a vial labelled 10 mg with purity 98.5%, water content 5% and TFA content 10% contains roughly 10 × 0.985 × 0.95 × 0.90, which is about 8.4 mg of peptide. If a method depends on the concentration being right, use the net figure, not the label. The reconstitution calculator takes whatever mg you enter, so enter the measured figure where you have it. Where a lab reports net peptide content directly, use that instead of multiplying.

7. How this catalogue handles it

8. Questions to ask any supplier

  1. "Can I see the batch-specific certificate before I buy?" A "general certificate for this product" is not batch-specific.
  2. "Which lab tested this batch, and how do I verify the report?" A real answer names the lab and gives you a way to check.
  3. "What is the purity figure, with decimals?" You want 98.7%, not "over 99%".
  4. "Is net peptide content or counterion reported?" If not, you cannot know the actual peptide mass.
  5. "Has the batch been tested for endotoxin?" Relevant for any cell or animal work.
  6. "What happens if the material does not match the certificate?" A real supplier has a written policy.
  7. "Can I send a sample to an independent lab?" The correct answer is "yes, please do".

9. Red flags in how a supplier behaves

10. If the material does not match

  1. Set the batch aside. Do not use it in further work until the question is settled.
  2. Contact the supplier with the independent result, the batch number and photos of the vial. Ask for a replacement, a refund or a written explanation.
  3. Keep the vial, the packaging and all correspondence.
  4. If there is no resolution, dispute the payment with your bank where the method allows it, and tell the community so the next person can check.
  5. If a supplier is advertising the material with therapeutic claims, that can be reported to the TGA.

11. The law in Australia, briefly

Lab resultsHow we sourceReconstitution calculatorFAQ