A Certificate of Analysis (COA) is the single most important trust document accompanying any research compound. It is an independent, third-party report that verifies what a vial actually contains. Learning to read one carefully is an essential skill for any research setting.
What a COA Documents
A complete COA typically includes:
- Product identity — the compound name and, where applicable, its CAS number or sequence.
- Batch / lot number — ties the document to a specific production run.
- Test date — when the analysis was performed.
- Purity result — usually expressed as a percentage.
- Analytical method — the technique used to determine purity and identity.
Purity by HPLC
The purity figure on most peptide COAs is determined by High-Performance Liquid Chromatography (HPLC). HPLC separates the components of a sample as they pass through a column, producing a chromatogram — a graph of detector response over time.
On the chromatogram:
- The main peak represents the target compound.
- Smaller peaks represent impurities or related substances.
- Purity is calculated as the area of the main peak relative to the total area of all peaks.
A result of "≥99% by HPLC" means the main peak accounts for at least 99% of the total measured area.
Mass Confirmation
Many COAs also include Mass Spectrometry (MS) data. Where HPLC tells you how much of the sample is the target compound, MS confirms the identity by measuring molecular weight. A reported mass that matches the theoretical molecular weight of the compound is strong evidence the correct molecule was synthesized.
Reading the Chromatogram
When a chromatogram is included, check:
- Is there a single dominant peak? A clean profile with one tall, sharp peak is ideal.
- Are impurity peaks small and few? Numerous or large secondary peaks warrant scrutiny.
- Does the retention time look consistent with the expected compound?
Matching the COA to Your Vial
A COA only means something if it corresponds to the material you received. Always confirm the lot number on the COA matches the lot number on the vial label. A COA for a different batch does not certify your specific product.
Summary
A COA is not a formality — it is verifiable evidence of identity and purity. Read the purity percentage, confirm the analytical method, check for mass confirmation, and always match the lot number to your vial. Every NorthLabs product page links to its third-party COA for exactly this reason.