What does peptide purity mean on a COA?

Purity is usually reported as a percentage from HPLC analysis, describing how much of the sample is the target peptide versus other peaks. A common research benchmark is 98 percent or higher, though the meaningful figure is the one measured for that specific batch.

What is HPLC and mass spec on a COA?

HPLC (high-performance liquid chromatography) separates the sample to measure purity as a percentage. Mass spectrometry confirms the molecular weight, verifying that the compound is the peptide it claims to be. Seen together, they answer is it the right peptide and how pure is it.

Quality & Testing · Research Use Only

How to read a Certificate of Analysis

Q: What is a Certificate of Analysis?

A Certificate of Analysis, or COA, is a lab document that reports the test results for a specific batch of a research compound. For peptides it typically lists identity, purity by HPLC, molecular weight confirmation by mass spectrometry, and the batch or lot number the tests apply to.

Q: Why does third-party testing matter?

A third-party COA is produced by an independent lab rather than the seller, which reduces the conflict of interest in self-reported numbers. Independent verification of identity and purity is a core part of due diligence in research material sourcing.

A Certificate of Analysis, or COA, is the single most useful document for judging a batch of research peptide. It reports what an independent test found for that specific lot. This guide explains the sections a COA contains, what purity and mass-spec figures mean, and why third-party testing is worth checking for.

Research use only. This page explains how to read laboratory testing documents for research material sourcing. It is not medical advice or human-use guidance. All products are sold strictly for research use and are not for human consumption.

What a COA is

A Certificate of Analysis is a lab report tied to a specific batch, or lot, of a compound. Rather than describing the product line in general, it states what testing found for the exact material in front of you. For peptides, a COA is the primary way to verify that a vial contains the compound it claims to, at the purity claimed.

The sections to look for

Product identity - the peptide name, sequence, and molecular formula the batch was tested against.
Batch or lot number - the code the results apply to. A COA is only meaningful if its lot number matches the vial you received.
Purity (HPLC) - a percentage from high-performance liquid chromatography, describing how much of the sample is the target peptide.
Molecular weight (mass spec) - a mass-spectrometry result confirming the compound weighs what the target peptide should, verifying identity.
Test date and lab - when the analysis was run and which lab ran it.

Reading purity and mass spec together

These two results answer two different questions. Mass spectrometry answers "is it the right peptide?" by confirming the molecular weight. HPLC purity answers "how pure is it?" by reporting the target peptide as a percentage of the whole sample. A common research benchmark is 98 percent or higher, but the number that matters is the one measured for that batch, not a general marketing claim. A high purity figure means little if the mass-spec identity does not match, so the two are read side by side.

Why third-party testing matters

A COA produced by an independent lab, rather than by the seller, reduces the conflict of interest in self-reported numbers. Independent verification of identity and purity is a standard part of due diligence when sourcing research materials. When comparing suppliers, checking whether a current, batch-matched, third-party COA is available is a practical first filter.

A quick checklist. Does the lot number on the COA match the vial? Is the test date recent? Was the lab independent of the seller? Does mass spec confirm identity, and does HPLC report a purity figure you are comfortable with? If all five line up, the batch has been meaningfully verified.

Frequently asked questions

What is a Certificate of Analysis?

A lab document reporting test results for a specific batch of a compound, typically identity, HPLC purity, mass-spec molecular weight, and the lot number the results apply to.

What purity should I look for?

A common research benchmark is 98 percent or higher by HPLC, but the meaningful figure is the one measured for that specific batch.

Why does third-party testing matter?

An independent lab has no stake in the numbers, so a third-party COA is a stronger check on identity and purity than a self-reported figure.

What do HPLC and mass spec tell me?

HPLC measures purity as a percentage; mass spec confirms the molecular weight and therefore identity. Together they answer whether it is the right peptide and how pure it is.

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