A Certificate of Analysis (COA) is the single most important document accompanying any research peptide. It is the manufacturer’s signed statement of what is actually in the vial — and for research use, “what is actually in the vial” is everything. This guide walks through each section of a typical COA so you can evaluate batches with confidence.
1. Identity: confirming you have the right compound
The top of every COA states the product name, molecular formula, molecular weight, and CAS number where one exists. Cross-check these against your order. Mass spectrometry (MS) data confirms the molecular weight matches the theoretical value — a deviation of more than a fraction of a percent is a red flag that the wrong sequence, or a truncated sequence, may be present.
2. Purity: the HPLC chromatogram
Purity is reported as a percentage derived from High-Performance Liquid Chromatography (HPLC). A reputable COA shows the actual chromatogram, not just a number. Look for a single dominant peak; the integrated area of that peak relative to all peaks gives the purity figure. Every batch we release is verified at ≥ 99% purity, and the chromatogram is included so you can see the baseline separation for yourself.
3. Net peptide content vs. gross weight
This distinction trips up many newcomers. The mass on the label is the gross fill weight, which includes counter-ions (typically acetate or TFA salts) and residual water. Net peptide content — often 70–90% of gross weight — is the actual mass of peptide. For accurate reconstitution math, always use net content where reported.
4. Residual solvents and water content
Synthesis and lyophilization leave trace solvents. A complete COA reports residual solvent levels and Karl Fischer water content. These should fall within established limits; unusually high water content can indicate poor lyophilization and reduced shelf stability.
5. Batch number and dates
Every COA is batch-specific. Record the batch number alongside your experimental data — reproducibility depends on it. The manufacture and retest dates tell you how fresh the material is and when re-analysis is recommended.
What a good COA looks like in practice
A trustworthy COA is batch-specific, shows the raw analytical traces, reports both gross and net mass, and is signed and dated. A “COA” that is a generic PDF with a round purity number and no chromatogram tells you very little. When every batch ships with an independent, third-party-verified COA, you remove a major source of variability before your experiment even begins.
For research use only. Not for human or veterinary use.