Lot-specific peptide Certificates of Analysis

Understanding your Certificate of Analysis

A peptide Certificate of Analysis is the laboratory report behind one specific lot: what the material is, how pure it is, and when it was tested. The short guides below explain how to read each part of the certificate and how the underlying testing works.

Purity testing vs identity testing

Purity — usually by HPLC — measures what percentage of the vial is the target compound. Identity — usually by mass spectrometry — confirms the compound matches the label. A material can pass one and fail the other, which is why every certificate reports both. The distinction is unpacked in Purity vs Identity: What Is the Difference?

How HPLC purity testing works

High-performance liquid chromatography separates a sample into its components and quantifies each one against a ≥99% purity specification. For how the method works and what its numbers mean, see HPLC Testing Explained.

How mass spectrometry confirms identity

Mass spectrometry measures molecular weight and matches it to the theoretical mass of the labeled compound. See Interpreting Mass Spectrometry on Peptide COAs and why HPLC alone isn’t enough.

Why testing is lot-specific

Results describe one production run, so a certificate is only meaningful when its lot number matches the vial in hand. Background: Why Lot Numbers Matter for Traceability.

Comparing certificates across batches

Repeat buyers can line up purity results, test dates and methods across lots of the same compound. A practical walkthrough: How to Compare COA Results Across Batches.

Start with common terms found on a COA or the overview of independent third-party peptide testing. For compound-level background, browse the Peptide Research Database or the research peptide catalog. New to lab reports? Start with How to read an HPLC purity report and What research-use-only means.