Testing & Quality
How to Read a Peptide Certificate of Analysis (COA)
Healthy Aminos Research Team · · 6 min read
Why COAs Matter
A Certificate of Analysis (COA) is a document issued by an analytical laboratory that reports the results of testing performed on a specific batch of material. For research-grade peptides, the COA provides objective evidence of identity, purity, and quality.
Key Sections of a Peptide COA
Identity (HPLC)
This section confirms that the compound is what it claims to be. The HPLC retention time of the sample is compared against a reference standard. A match within an acceptable window (typically ±0.5 minutes) confirms identity.
Purity (HPLC)
Purity is expressed as the percentage of the total chromatographic area corresponding to the target peptide peak. Research-grade peptides typically range from 95-99%+ purity. Higher purity means fewer synthesis-related impurities.
Mass Spectrometry (MS)
Mass spectrometry confirms the molecular weight of the compound. The observed mass should match the theoretical molecular weight within the instrument's accuracy (typically ±1 Da for ESI-MS). This provides orthogonal confirmation of identity beyond HPLC retention time.
Endotoxin Testing
Endotoxins are lipopolysaccharide components of gram-negative bacterial cell walls. They can interfere with biological assays. The Limulus Amebocyte Lysate (LAL) assay is the standard method. Results should be below the specified threshold (typically <0.5 EU/mg).
Sterility Testing
Confirms the absence of viable microorganisms. Important for any compound used in cell culture or sensitive research applications.
Peptide Content
Reports the actual peptide mass as a percentage of the total vial weight (which includes counter-ions, moisture, and residual solvents). Typical values range from 60-85%. This is NOT the same as purity — a 98% pure peptide might have 75% peptide content.
Red Flags
- Missing batch number (a COA should be traceable to a specific batch)
- No laboratory name or accreditation information
- Purity reported without a chromatogram image
- Mass spec data showing multiple peaks of similar intensity
- No date of analysis