What a COA is for
A Certificate of Analysis summarizes analytical results for a specific lot. For research peptides, it is the primary document linking the vial in hand to measured identity and purity claims. Reading it carefully is part of incoming quality control — not a substitute for your own method verification when a study requires it.
Annotated field guide
1.Product / compound name
Confirms the intended analyte. Cross-check spelling and any salt or acetate form notes against your purchase order.
2.Lot / batch number
Unique identifier for chain-of-custody. Record this on every aliquot label and notebook entry.
3.Purity (%)
Usually HPLC area-percent or a stated method. Know whether the number is chromatographic purity vs. content by a different assay.
4.Test method
Names the technique (e.g., HPLC-UV, LC-MS). Method identity matters when comparing lots or labs.
5.Appearance
Physical description of the received material (e.g., white lyophilized powder). Useful for visual incoming inspection.
6.Expiration / retest date
Manufacturer or lab-stated dating under defined storage. Treat as a quality planning input, not a use instruction.
HPLC purity — reading the peaks
Purity percentages often come from integrating chromatographic peak areas. A dominant peak near the expected retention time is typically assigned to the target; smaller peaks may be process-related impurities or degradants depending on the method.
- A — Target compound peak
- B — Retention time axis
- C — Minor impurity region
When reviewing a chromatogram attachment:
- Confirm the method wavelength or detector type matches the COA narrative.
- Note whether purity is reported as area % above a stated threshold.
- Flag lots where impurity peaks approach laboratory-defined review limits.
Mass identity confirmation
Many COAs include mass spectrometry results comparing an expected molecular mass to an observed value.
-0.02
Example peptide identity check: Within typical identity window
A small delta supports identity consistency under the stated ionization conditions. Large unexplained deltas warrant laboratory review before the lot is released into critical assays.
Independent verification
Third-party ISO 17025–oriented testing labs add an independent measurement trail. That does not remove your responsibility to align COA claims with your protocol’s acceptance criteria, but it strengthens lot documentation and chain-of-custody narratives.
Practical review checklist
- Match vial label lot ID to the COA lot ID exactly.
- Archive a PDF copy with the study records.
- Note method names, purity basis, and any unresolved impurities in your QC log.
- If appearance on receipt disagrees with the COA description, quarantine and investigate before use in analytical work.
Sources & references
- ISO/IEC 17025 overview materials on competence of testing and calibration laboratories.
- FDA guidance documents on analytical procedures and method validation (high-level reference).
- Pharmacopeial and analytical laboratory bulletins describing HPLC purity reporting conventions.