How to Read a Peptide Certificate of Analysis
A certificate of analysis (COA) records results for a submitted sample. Reading it starts with identifying what was tested, which lot it represents, and which methods were used. A percentage alone cannot answer all three questions. This guide is for evaluating laboratory documentation; it does not provide instructions for human use.
Start with identity and traceability
Compare the sample name, supplier, product identifier, and lot or batch number with the material in your records. A familiar product name is not enough: two lots can have different results. If a report uses an abbreviated sample name, request documentation connecting that name to the supplied material rather than assuming they are interchangeable.
Separate the dates
A received date, analysis date, report issue date, and manufacturing date describe different events. Preserve the labels used by the laboratory. A recently issued report does not by itself establish when the material was manufactured, and an analysis date is not an expiration date.
Read each measurement on its own terms
Identity, chromatographic purity, and quantity answer different questions. A purity percentage does not establish the milligrams in a vial. Check whether quantity is reported per vial, per tablet, or per milliliter. Do not convert between these without the additional information the calculation requires.
Look for scope and limitations
Check the analytical method, units, number of samples, and any qualifying notes. A mean across several vials is not the measured result of every vial. A blank field, pending result, or test that is not listed should not be treated as a pass. Purity and mass analysis alone do not establish sterility, clinical safety, or suitability for human use.
Verify the original record
Keep the complete, unchanged report, including laboratory identity and all pages. Where the laboratory provides a verification service, compare the report number and details with that record. Ask the issuer about conflicting units, missing pages, or an unclear sample description before relying on the results.
A short review checklist
Before using a COA in a research record, confirm: matching sample and batch; clearly labeled dates; method and units; all pages; any pending or missing tests; and a traceable original report. Record unresolved questions explicitly. A COA supports evaluation of a tested sample—it is not a blanket certification of a supplier's entire catalog.
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