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Testing

What each lab test measures, what a certificate of analysis can and cannot tell you, and how to check one with the issuing lab. Method explainers only: no product or vendor endorsements.

Hub reviewed by Amino Wire Editorial Team · October 19, 2026

In short

A peptide certificate of analysis usually reports two things: HPLC purity (how clean the sample is) and mass spectrometry identity (whether it is the right molecule). Amount, endotoxin and sterility are separate tests. Every report covers only the sample tested, and should be verified on the issuing lab's own site.

Explainers

7 pages

  1. Testing literacy

    How third-party peptide testing works, from vial to certificate

    What happens when a peptide goes to a third-party lab: who sends samples, which tests exist (HPLC, LC-MS, endotoxin, sterility), and what a report can't show.

  2. Method explainer

    HPLC purity: what the percentage on a peptide COA means

    How HPLC measures peptide purity, what area-percent really reports, why 99% purity can still mean the wrong amount or peptide, and how to read a trace.

  3. Method explainer

    Mass spectrometry: how labs confirm a peptide is what the label says

    How LC-MS confirms peptide identity by molecular mass, what charge states and adducts look like on a report, and the limits of mass-only identity checks.

  4. Method explainer

    Net peptide content: why a ‘10 mg’ vial may not hold 10 mg of peptide

    The difference between purity, gross weight and net peptide content; counter-ions like TFA and acetate; and how labs measure what's actually in a vial.

  5. Method explainer

    Endotoxin testing: the test a purity number can’t replace

    What bacterial endotoxins are, how LAL and recombinant tests measure them in EU, why injectables need them, and why most peptide COAs don't include them.

  6. Method explainer

    Sterility testing: what it detects and what a ‘pass’ means

    How sterility testing works (compendial culture vs rapid PCR methods), what a pass does and doesn't prove, and how it differs from endotoxin testing.

  7. Checklist

    How to verify a peptide COA in seven checks

    A seven-step check for any peptide certificate of analysis: lab verification codes, lot matching, tests actually run, dates and red flags.

Testing FAQ

What does HPLC purity on a peptide COA mean?

It is usually the main peak's share of all UV-detected peak area at one wavelength. It shows how clean the sample is relative to other UV-absorbing material. It does not confirm identity or measure milligrams.

How is peptide identity confirmed?

With mass spectrometry, usually LC-MS. It shows whether the main component has the expected molecular mass for the labeled peptide, which catches substituted peptides that can look pure on HPLC.

Does a purity test show a vial is free of endotoxin or sterile?

No. Endotoxin (LAL or recombinant factor C) and sterility testing are separate tests that must be ordered. A purity or identity report says nothing about them.

How do I verify a certificate of analysis?

On the issuing lab's own website, using the report number or key printed on the COA, never through a link on the seller's site. Then check the lot number, compound, amount, tests run, and test date.