How to read a COA

What a COA is, and what it is not

A certificate of analysis (COA) is a report from a laboratory describing the results of specific tests run on a specific sample. The important word is specific. A COA describes one sample, drawn from one lot, tested by named methods on a stated date. It is not a general statement about a compound, a brand, or every vial a seller has ever shipped.

Read a COA as evidence for a narrow claim: this sample, from this lot, gave these results by these methods. Everything else is inference.

Start with the header

Before looking at any number, check that the document identifies itself properly. A usable header normally shows:

• Laboratory name and physical address.
• Report ID or certificate number, unique to this report.
• Date the sample was received and date of analysis or report.
• Sample name as submitted, and the lot or batch number.
• Client or submitter name.
• Signature or name of the reviewing analyst, when the lab provides one.

Identity: is it the expected molecule?

Identity is usually shown by mass spectrometry, often written as LC-MS, ESI-MS, or MALDI-TOF. The report compares the observed mass to the theoretical mass of the expected molecule. A match within the lab's stated tolerance supports identity.

Mass spectrometry answers "is the expected molecule present". It does not by itself answer "how much" or "what else is in the vial".

Purity: how clean is the peptide fraction?

Purity is usually measured by HPLC with UV detection. The instrument separates the components of the sample, and the report gives the area of the main peak as a percentage of the total peak area at a stated wavelength.

This is a relative measure among the things the detector can see. Water, many salts, and other components that do not absorb at that wavelength are not counted. That is why purity and net peptide content are different numbers, covered in a separate guide.

A purity figure is much more credible when the chromatogram itself is attached, with the peak table, the method, and the wavelength. A bare percentage with no trace behind it is a weak document.

Other tests you may see

Some COAs include additional tests, such as net peptide content, water content, endotoxin, residual solvents, or heavy metals. Only treat a property as tested if the report names the test, the method, and the result. If a test is not on the report, it was not reported, regardless of what a product page says.

A quick checklist

• The lot number on the COA matches the lot number on the vial label.
• The lab is named and can be contacted independently of the seller.
• The report ID can be verified with the lab. See the guide on checking a lab report ID.
• Dates make sense: the analysis is not dated before the lot existed.
• Raw data is attached: chromatogram and mass spectrum, not just a summary number.
• The same report is not reused across different lots or products.

M Bio documentation status

M Bio publishes original supplier references in its Lab Results library. These documents retain the issuing laboratory, original client, tested sample, and lot. They are not confirmed M Bio lot certificates. Matching reports are marked pending where no suitable reference is available. Verify each document and its scope before drawing a conclusion about a received material.