How to read a peptide COA: what a testing report can and cannot tell you
AI-generated conceptual illustration. This is not an actual COA, measurement, or certification.
A certificate of analysis, usually shortened to COA, is a record of reported testing. Its value comes from connecting a clearly identified material to specific tests, results, and acceptance criteria. Start with that connection before judging a supplier by a large purity percentage. The pharmaceutical manufacturing guidance ICH Q7 describes these elements in its section on certificates of analysis. ICH Q7, section 11.4.
For a beginner, the most useful question is: What does this document actually establish about the material I am evaluating? Our approach is to separate three decisions: whether the record matches the material, whether the tests answer your questions, and whether the remaining uncertainty is acceptable for the proposed laboratory work.
First, match the report to the material
Read the compound name and batch number before the result. Q7 describes certificates containing the material name, batch identification, release information, tests, acceptance limits, and results. It also addresses authorization and identifying the manufacturer or testing laboratory when certificates pass through intermediaries. These are useful document-reading reference points, not proof that an individual research supplier complies with pharmaceutical manufacturing standards. ICH Q7, sections 11.40–11.44.
Our suggested worksheet has four separate entries: the lot offered by the supplier, the lot on the report, the report identifier, and how the connection was verified. If two lot numbers differ, write down the mismatch. Do not silently assume they refer to the same material.
Also record what remains unknown. Was the submitted sample finished material, bulk powder, or something else? Who selected it? Does the document explain how it represents the lot being offered? Treat unanswered questions as questions, rather than upgrading them to proof of quality or accusations of misconduct.
Identity, purity, and amount are different questions
| Question | What you are looking for | Interpretation to avoid |
|---|---|---|
| What substance is this? | An identification result supported by an appropriate method | Assuming a familiar label proves identity |
| What impurities were assessed? | The named analytical procedure and its impurity results | Reading one result as a search for every possible contaminant |
| How much substance is present? | A quantitative assay with units and a stated basis | Treating a purity percentage as a vial-content measurement |
ICH Q6A treats identification, assay, and impurity testing as distinct analytical questions. It also explains that a single chromatographic retention time is not sufficiently specific identification on its own. The same technique can support different questions when the procedure is designed appropriately; the instrument name alone does not tell you what was measured. ICH Q6A, section 3.2.
Our reading rule is simple: next to each number, write its test name, units, and meaning. If you cannot explain those three things, leave the interpretation open rather than turning the number into a purchasing conclusion.
A worked document-reading example
The following is fictional and describes no actual supplier or laboratory.
Imagine a listing labeled “Research Compound A, lot PX-104.” Its attached document names PX-103, reports “purity: 99%,” and contains no quantitative vial-content result.
The useful note is not “this supplier passed” or “this supplier is a scam.” Write:
- Lot connection: unresolved because the identifiers differ.
- Purity: a result is present, but its method and reporting basis need clarification.
- Vial content: not established by the supplied document.
- Next assessment step: obtain matching documentation and resolve the interpretation before assigning a recommendation.
This example demonstrates a way to organize uncertainty. It is not a universal pass/fail specification or a testing protocol.
Keep missing tests visible
Q7 discusses microbiological and endotoxin specifications separately from other impurity controls. A document-reading checklist should therefore keep those questions separate instead of treating a purity result as an answer to them. Which specifications matter depends on the material and the work being evaluated. ICH Q7, section 11.13.
Our recommendation is to use explicit worksheet labels: “result supplied,” “not supplied,” “verification pending,” and “not applicable, with reason.” Avoid a blank cell that another reader could mistake for a completed check.
Check the scope of the source, too
Analytical guidance must be read within its scope. ICH Q6B explicitly excludes synthetic peptides and does not apply to regulation of preclinical or clinical research material. It should not be presented as the governing checklist for an ordinary synthetic research-peptide vial. ICH Q6B, section 1.3.
The guidance cited here provides context for reading analytical documentation. It does not certify a vendor, authorize a product for human use, or replace a laboratory’s material-specific assessment.
Turn the report into an evidence record
Use the supplier evidence worksheet to keep the claim, document, verification, and unresolved issue together. Read the assessment methodology before interpreting a directory status. A recommendation should be supported by the complete record, not by the most impressive-looking number on the page.