Decoding a Certificate of Analysis: Quality Indicators
The certificate of analysis (CoA) is the reference document for evaluating peptide quality. Here is how to read it:
HPLC PURITY High-performance liquid chromatography separates the components of a sample. The percentage indicates the proportion of the target peptide relative to impurities.
- Excellent: >98%
- Acceptable: 95-98%
- To avoid: <95%
Impurities are usually truncated peptides (incomplete synthesis) or degradation products.
MASS SPECTROMETRY (MS) The observed molecular mass must match the theoretical mass calculated from the sequence.
- Acceptable deviation: ±0.1%
- A larger deviation may indicate chemical modification or synthesis error
APPEARANCE The description of appearance (white powder, lyophilisate) verifies consistency with the product received.
NET PEPTIDE CONTENT Note: a vial labeled "5mg" rarely contains 5mg of pure peptide. Net content is typically 70-85%, the rest being salts (TFA, acetate) and residual water.
The CoA must specify this ratio to allow accurate dosage calculation. Serious suppliers always indicate this information.
Beware of generic CoAs or those without a specific batch number: they may not correspond to the product actually delivered.
