Guide
How to read a peptide certificate of analysis
A certificate of analysis reports what a named laboratory measured on one specific batch. A usable one names the batch, states each method, gives a result against a specification, and is traceable to the laboratory that issued it. A purity figure with no batch number and no issuing laboratory is a marketing claim, not a result.
Match the sample before comparing numbers
Start with the lot number, compound, formulation, issuing laboratory and report date. A product name alone does not identify the sample you are holding. A laboratory report applies to the submitted sample; it does not by itself verify every vial in a batch or a supplier’s complete production process.
The fields to read together
Identity depends on the method
A mass-spectrometry result and an HPLC retention-time comparison are different forms of evidence. Retention-time matching compares a chromatographic result with a reference under stated conditions. Mass spectrometry measures mass-to-charge information. Neither should be substituted for the other in a summary, and mass alone does not prove every aspect of a peptide sequence.
HPLC purity is not peptide mass
A purity percentage calculated from chromatographic peak areas describes the peaks included in that calculation under the stated method. It is not the percentage of the vial’s total mass that is peptide. Check the wavelength, integration rules and any exclusions in the laboratory notes.
Net peptide content and label amount are different fields
Read the amount reported for the tested sample in its stated units. Do not derive it by multiplying a label amount by an HPLC purity percentage. For a blend, a total does not establish each component amount unless those component results and their method are separately reported.
Read contaminant results literally
Not detected means the analyte was not detected under the method and its applicable detection limits; it does not mean mathematically zero. A blank field does not mean a pass. A Reported status is not a Pass status. An unlisted test must not be described as completed.
Compare the website with the original
Use the laboratory verification link and the issued PDF where available. Compare the report identifier, sample and important results. If versions disagree, preserve both and request clarification. Do not silently pick the more favorable result.
Separate analytical evidence from other decisions
An analytical report does not establish delivery reliability, manufacturing origin, clinical effectiveness or suitability for human or veterinary use. These are distinct questions requiring different evidence.
Common questions
What should a peptide COA include?
Look for the sample and lot, issuing laboratory, report date, methods, results with units, and applicable specifications. Verify the original rather than relying only on a seller’s summary.
Does 99% HPLC purity mean 99% of the vial is peptide?
No. HPLC peak-area purity and net peptide content are different measurements. Read the method and the separate content result.
What should I do when the PDF and verification portal disagree?
Save both versions and ask the issuing laboratory to identify the applicable record. Treat the discrepancy as unresolved until the source is clarified.
References
- ICH Q6B: Specifications — Test Procedures and Acceptance Criteria for Biotechnological/Biological Products — International Council for Harmonisation (ICH)
- ICH Q2(R2): Validation of Analytical Procedures — International Council for Harmonisation (ICH), 2023
- Related impurities in peptide medicines — D'Hondt M et al., Journal of Pharmaceutical and Biomedical Analysis, 2014
- Pyrogen and Endotoxins Testing: Questions and Answers — U.S. Food and Drug Administration, guidance for industry
From the catalog
Compounds referenced on this page
For laboratory research use only. Not for human or veterinary consumption.