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How to Read a Peptide Label and a Certificate of Analysis
A vial label and a certificate of analysis (COA) should tell the same story. Here is how to check that they do.
On the vial label
- Compound name and amount per vial (for example, 10 mg).
- Lot or batch number, the code that links the vial to its test results.
- Storage instructions and the statement that the product is for research use only.
On the certificate of analysis
- Lot number: it must match the one on your vial.
- Testing laboratory and date of analysis.
- HPLC result. High-performance liquid chromatography separates the sample into its components. The report shows a chromatogram and a purity figure, usually the share of the main peak.
- Mass spectrometry result. It measures the molecular weight of the compound, which confirms that the product is what the label says it is.
What a purity figure does and doesn't mean
HPLC purity describes how much of the detected peptide material is the target compound. It does not mean that 99% of the powder is peptide. A lyophilized powder also contains water and salts (counter-ions), so the peptide content by weight is lower. Some reports include a separate peptide-content figure.
Red flags
- No lot number, or a lot number that doesn't match your vial.
- No laboratory name or date.
- No chromatogram, just a purity number.
- A report that looks identical across different lots.
- No method listed (HPLC, mass spectrometry).
Before you order
Check that the product page offers a COA for the lot you will receive, and compare the lot number when your order arrives.