Guide

COA red-flag checklist

Work through these checks when you evaluate a certificate of analysis. Each one separates a defensible analytical record from a marketing document.

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A purity percentage with no stated method
A purity figure is only meaningful with a named method (e.g. reverse-phase HPLC/UPLC at a stated wavelength).
No chromatogram image
Without a chromatogram you cannot see the main-peak integration or the impurity profile behind the number.
No LC-MS identity confirmation
Purity without identity does not establish what the material actually is; expect an observed-vs-expected mass.
Lot number does not match the vial label
The COA, vial label, and catalog lot must agree, or the document cannot be tied to the material in hand.
No issuing laboratory or accreditation named
Independent third-party testing under ISO/IEC 17025 carries more evidentiary weight than an anonymous or supplier-only document.
No water-content (Karl Fischer) result for a lyophilized peptide
Residual water affects net peptide content and stability; a complete COA reports it.