A Certificate of Analysis (COA) is the document that records the quality-control test results for a specific batch of material. In research, it is the foundation of an experiment's reproducibility.
What a COA should contain
- Material identification: name, sequence, CAS number where one exists, formula and molecular weight.
- Batch number and manufacturing and analysis dates. The COA applies to that batch — not to the product in general.
- Purity by HPLC, with the chromatogram attached and the analytical conditions (column, gradient, wavelength).
- Identity by mass spectrometry (MS), comparing observed mass with theoretical mass.
- Responsible laboratory, signature and, ideally, a way to verify it independently.
Red flags
- A COA with no batch number, or the same document reused for different batches.
- Purity stated without a chromatogram.
- No mass spectrometry data — HPLC purity alone does not prove the molecule is the right one.
- A laboratory that cannot be identified or contacted.
Purity is not everything
A material that is “99% pure” by HPLC can still contain contaminants the method does not detect, such as endotoxins, residual solvents or counter-ions (for example TFA). For cell-culture work, these parameters can matter as much as the headline purity.
To understand the techniques behind these numbers, read our article on HPLC and mass spectrometry.