Quick answer: a Certificate of Analysis (COA) is the document that states what is actually in the vial. A useful research COA confirms identity by mass spectrometry, purity by HPLC, and carries the batch number that ties the report to the vial on your bench.
What a COA is for
A COA is a lab report issued for one specific batch of material. Its job is simple: prove that the compound is what the label says, and state how pure it is. In research that matters because an unverified material introduces a variable you cannot control. If the peptide is 90% pure instead of 99%, every downstream measurement is off by an unknown amount.
The four sections that matter
1. Identity
Identity is confirmed by mass spectrometry (MS). The lab measures the molecular mass of the sample and compares it with the theoretical mass of the sequence. A match within instrument tolerance means the right molecule is present. Look for the observed mass, the expected mass, and a pass or fail statement.
2. Purity
Purity is measured by high-performance liquid chromatography (HPLC). The sample is separated into its components and the area under the main peak is reported as a percentage of the total. A 99.2% figure means 99.2% of detected material was the target peptide. Ask for the chromatogram, not just the number, so you can see whether secondary peaks exist.
3. Batch and lot number
The batch number on the COA must match the number on the vial. A COA without a batch number, or one reused across products, tells you nothing about the material in your hand.
4. The testing lab
A COA should name the laboratory that ran the test and give you a way to verify it. Third-party means the vendor did not run the test themselves. If the vendor is also the lab, treat the report as a claim rather than evidence.
Red flags
- No batch number, or one that does not match the vial.
- A purity figure with no chromatogram.
- A generic report with the product name typed in but no instrument data.
- A lab you cannot find or contact.
- A report dated years before the product listing.
How Browse Peptides publishes COAs
Every batch we list is tested by an independent laboratory before it goes on sale. The report is published on our COAs page with the batch number, and a printed copy ships with the order so the vial and the document travel together.
Sources
- International Council for Harmonisation, ICH Q6B: Specifications for Biotechnological/Biological Products.
- United States Pharmacopeia, General Chapter 621, Chromatography.