Understanding peptide purity discrepancies
Independent testing compares your submitted material with the supplier's documentation. A difference needs interpretation: it can reflect sample handling, analytical methods, integration, or a genuine quality issue. It is not automatically evidence of fraud.
Compare like with like
Confirm the batch or lot identifier, sample format and dates on both reports. HPLC purity depends on the method, detector wavelength and which peaks are integrated. Net peptide content, water and counterions are separate measurements. A chromatographic purity number is not a complete measure of the material in a vial.
What to check on a Certificate of Analysis
- The sample and lot identifiers match the material you have.
- The analytical method and measured result are stated with units.
- Supporting chromatograms or spectra correspond to the tests ordered.
- Specifications and reporting limits are stated.
- Any comparison accounts for method differences and uncertainty.
Purity and identity answer different questions
HPLC purity testing separates the main component from detected impurities under the selected chromatographic method. Mass spectrometry compares observed mass with the expected compound. Neither test alone establishes every structural feature, biological activity or clinical safety.
Truncated sequences, deletion sequences, oxidation and other degradation products are possible quality concerns. Endotoxin, residual solvents and heavy metals require separately selected panels. Their prevalence cannot be inferred from a purity result.
