How to Read a Certificate of Analysis for a Recombinant Protein
Lot number, methods and reported results: what each part of a recombinant protein Certificate of Analysis tells a laboratory buyer.
What a Certificate of Analysis Covers
A Certificate of Analysis (CoA) is a lot-specific document recording how one batch of material was tested and what was observed. It should identify the product name, catalogue number, lot number, date of manufacture and date of analysis. Each reported parameter is paired with the method used to obtain it. A CoA describes the lot in hand, not the catalogue item in general, so a buyer should match the lot number on the document to the label on the vial. Without that match, the data has no standing. Where a specification is stated, a lot passes when the measured result is ≥ the criterion for that parameter.
Methods Matter More Than Results
Two CoAs may report the same parameter through different techniques, and the figures are meaningful only alongside the method. Purity measured by SDS-PAGE and purity measured by HPLC answer different questions and are not interchangeable. The same applies to identity, which may be confirmed by mass spectrometry, peptide mapping or western blot. Read the method column before the result column. If a method is not stated, ask the supplier how the value was obtained and under what conditions, so the figure can be interpreted correctly rather than assumed.
What the CoA Does Not Tell You
A CoA is a record of testing, not a regulatory certificate. It does not by itself establish that a material is suitable for a particular application, nor does it replace an in-house qualification. It also says nothing about how the material will behave after reconstitution, freeze—thaw cycling or extended storage under your own conditions. Treat the CoA as the starting point of your incoming-goods check: confirm identity, review the lot data against your specification, and run the assay that matters for your workflow. Where a value is absent, ask.
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