How to Read a Certificate of Analysis

A Certificate of Analysis (COA) is a document from an analytical testing laboratory certifying the composition of a specific batch of material. For research peptides, a COA should confirm identity, purity, and the absence of specified contaminants. Knowing how to read one is essential for any serious researcher.

What a COA Should Contain

1. Testing laboratory name and accreditation

The COA should originate from an independent third-party laboratory, not the supplier's internal QC team. Look for ISO 17025 accreditation or equivalent. The lab name, address, and ideally an accreditation number should be present.

2. Lot number

This is the most important field to verify. The lot number on the COA must match the lot number printed on your vial label exactly. A COA without a matching lot number is essentially worthless — it may belong to a different batch entirely.

3. HPLC purity

Expressed as a percentage (e.g., ≥98% by HPLC). This value represents the proportion of the target compound relative to all UV-absorbing material in the sample. See our HPLC article for a detailed explanation of how this is calculated.

4. Mass spectrometry (MS) identity confirmation

Mass spec confirms the molecular weight of the compound, verifying that you have the correct compound — not just any high-purity material. For peptides, this is a meaningful additional test beyond purity alone.

5. Heavy metals panel (optional but preferred)

Testing for arsenic, lead, cadmium, and mercury. Standard thresholds follow USP or ICH Q3D guidelines. Not all COAs include this — it's a premium test that adds credibility.

Red Flags to Watch For

• No lab name, or only the supplier's own internal testing listed
• Lot number missing or not matching the product label
• Purity listed without specifying the analytical method used
• No date on the analysis — COAs should be from the current production year
• A single generic COA used across multiple products or lots

Verifying Your Lot

Always verify the lot number against the supplier's documentation before using a compound in research. You can verify any lot we ship using our Verify page — enter the lot number from your vial label to pull the COA for that exact batch.