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How to read a COA for research peptides

A certificate of analysis tells you what a lab found in one batch of material. This guide walks through each part of the report, what the numbers mean, and how to confirm the report is real.

Main peak: the target compound Its area as a share of all peaks is the purity figure Impurity Impurity Retention time Detector response
An HPLC chromatogram. Most COAs include one, and the purity percentage is calculated from it.

What a COA is

A certificate of analysis is a report from an analytical laboratory. A sample from a batch of material is sent to the lab, the lab runs a defined set of tests, and the COA records the results.

Three questions matter most for a research peptide. Is it the compound named on the label? How much of the material is that compound? How much is in the vial? A complete COA answers all three, and it names the batch the answers apply to.

A COA is only as good as its source. A report from a third-party lab that you can look up on the lab’s own website carries far more weight than a document the seller produced in-house.

The parts of a report

Layouts differ from lab to lab, but the same fields appear on nearly every report. The numbers below match the notes that follow.

Certificate of analysisExample Analytical Lab
1
Client
Example Vendor
2
Sample and batch
Peptide X, 10 mg vial, lot AB1234
3
Dates
Received 02 Mar, reported 06 Mar
4
Purity (HPLC)
99.1%
5
Identity (MS)
Observed mass matches theoretical
6
Content
10.4 mg per vial
7
Verification key
EX-000000

Illustrative layout with made-up values. It is not a real report.

  1. 1

    Client

    Who submitted the sample. Check whose material the report describes. A report issued to a different company tells you about that company’s material.

  2. 2

    Sample and batch

    The compound, the stated amount, and the batch or lot number. The lot number is the link between the report and the vial. Ask whether it matches the lot being supplied.

  3. 3

    Dates

    When the lab received the sample and issued the report. The dates should make sense for the batch. A report from years ago attached to current stock deserves a question.

  4. 4

    Purity

    The percentage of the detected material that is the target compound, usually measured by HPLC. More on this below.

  5. 5

    Identity

    Confirmation that the compound is what the label says, usually by mass spectrometry.

  6. 6

    Content

    The measured mass of the compound in the vial, in milligrams. This is a separate result from purity.

  7. 7

    Verification key

    A report number, key, or QR code you can use on the lab’s website to pull up the original record.

Purity and the chromatogram

High-performance liquid chromatography separates a sample into its components. Each component leaves the instrument at a different time and shows up as a peak. The chart of those peaks is the chromatogram at the top of this page.

The purity figure is the area under the main peak divided by the total area under all peaks. A result of 99.1% means the target compound accounts for 99.1% of what the detector saw, and the remaining 0.9% is other material such as truncated sequences or synthesis by-products.

When a report includes the chromatogram, look for one dominant, sharp peak and a flat baseline. Several sizeable secondary peaks, or a main peak with a pronounced shoulder, are worth comparing against the stated percentage.

Identity by mass spectrometry

Purity says how clean a sample is. It does not say what the sample is. Mass spectrometry measures the molecular mass of the compound, and the lab compares the observed mass with the theoretical mass for the named peptide.

Every peptide has a known theoretical mass. Tesamorelin, for example, is approximately 5,136 Da. An observed mass that agrees with the theoretical value confirms identity. A report that shows purity alone, with no identity test, leaves that question open.

Content per vial

Content is the measured amount of compound in the vial. A vial labelled 10 mg might measure 10.4 mg or 9.6 mg. Some variation is normal in filling, and labs report the figure they measured.

Purity and content are easy to confuse, and they answer different questions. A vial can test at 99% purity and still hold noticeably less than the label states. For laboratory work where concentration matters, the measured content is the number to work from.

Verifying with the lab

A PDF or a screenshot can be edited. A record on the lab’s own website cannot be changed by the vendor. Verification takes about a minute:

  • Go to the lab’s website by typing the address yourself or scanning the QR code on the report.
  • Enter the report number or verification key.
  • Check that the compound, batch number, and results match the document you were given.

Here is a live example: a Quantis Labs verification record for a Tesamorelin batch. Open it and compare each field against the list above.

Red flags

  • No batch or lot number on the report.
  • No way to look the report up on the lab’s website.
  • The seller will not say whether the report covers the lot being supplied or a representative sample.
  • One report is presented as proof for many different products.
  • Purity is given with no identity test and no content figure.
  • Blurry text, mismatched fonts, or numbers that look pasted in.
  • Dates that are old relative to the stock being sold.

What a COA cannot tell you

A COA describes the sample the lab received. A batch-specific report applies to that batch. A representative sample report shows what was found in the sample tested and does not establish the results for every other batch. Neither says anything about how a vial was stored or shipped afterwards.

A report also covers only the tests that were run. If a test is not listed, the material was not checked for it. Read the list of methods as carefully as the results.

Ask for the report with your quote

Selected Cryonix materials are independently tested, and Premium US inventory offers tested batches with QR-linked COAs. Tell us the material and specification, and we will confirm which report applies and how it relates to the lot being supplied.

Request a quote Testing & COAs

Common questions

What is the difference between purity and content?

Purity is the share of the detected material that is the target compound, given as a percentage. Content is the measured mass of the compound in the vial, given in milligrams. A complete report shows both.

Can a COA be faked?

A document can be edited. The record on the testing lab’s website cannot be edited by the vendor. Look the report up there and check that the details match.

Does one COA cover every batch of a product?

No. A COA describes the sample or batch named in the report. Ask whether the report is batch-specific or a representative sample, and whether the supplied lot matches it.

Does a COA mean a product is approved for human use?

No. A COA reports analytical results for a material. It is not a clinical or regulatory approval of any kind.

More guides

Cryonix materials are supplied for laboratory research only. They are not for human or animal use. This guide is general information about analytical documentation.