A Certificate of Analysis, or COA, is the single most important document that accompanies any research compound. It is the lab's signed statement of what is actually inside the vial — not what the label claims, but what independent testing measured. For any researcher, learning to read a COA properly is the difference between trusting a marketing number and verifying a result.
What a Certificate of Analysis actually is
A COA is a document produced by an analytical laboratory after testing a specific batch of a compound. The key word is batch. A COA is not a general claim about a product line — it applies only to the exact batch identified by the batch number printed on it. A reputable supplier issues a fresh COA for every production batch, because purity and identity can vary from one synthesis run to the next.
When you receive a research compound, the batch number on your vial should match the batch number on the COA. If it doesn't, the certificate tells you nothing about what you actually received.
The identity test
Before purity even matters, a lab confirms that the compound is what it claims to be. This is the identity test, usually performed by mass spectrometry (MS) or nuclear magnetic resonance (NMR). Mass spectrometry measures the molecular weight of the compound and compares it to the known theoretical weight of the target molecule. If the measured mass matches, the identity is confirmed.
On a COA you will typically see this listed as "Identity: Confirmed" alongside the analytical method used. A confirmed identity means the molecule present is structurally the one named on the label.
The purity result
Purity is usually the headline figure, expressed as a percentage and measured by high-performance liquid chromatography (HPLC). A result of 99.2% purity means that 99.2% of the material in the sample is the target compound, and the remaining 0.8% consists of related impurities, synthesis byproducts, or residual solvents.
For research applications, purity above 98% is generally considered acceptable, and many suppliers target 99% or higher. What matters is not just the number but the chromatogram behind it — the visual trace showing each detected peak. A clean chromatogram shows one dominant peak with minimal smaller peaks beside it.
Heavy metals and microbial screening
Beyond identity and purity, a thorough COA includes safety screening. Heavy metals testing measures contamination from elements like lead, arsenic, and mercury, typically reported in parts per million (ppm). A result such as "<0.5 ppm" indicates contamination below the detection threshold.
Microbial testing screens for bacterial and fungal contamination. A "Pass" result indicates the sample meets the laboratory's microbial limits. These tests matter because even a high-purity compound can carry contaminants introduced during handling or storage.
Verifying a COA is genuine
A COA is only as trustworthy as the lab that issued it — and the ability to verify it independently. The strongest standard is a publicly searchable result. When a third-party lab such as Janoshik Analytical publishes results to a public database, anyone can enter the batch number and pull the original report directly from the lab, bypassing the supplier entirely.
This is the gold standard: you are not trusting the supplier's word, and you are not trusting a PDF that could be edited. You are reading the lab's own published result. If a supplier cannot point you to an independently hosted, verifiable COA, treat their purity claims with caution.
A quick checklist
When you next read a Certificate of Analysis, work through these questions: Does the batch number match your vial? Is the identity confirmed by mass spec or NMR? Is the purity figure backed by a clean chromatogram? Are heavy metals and microbial results within limits? And critically — can you verify the result independently on the testing lab's own public portal? If all five check out, you are holding a document worth trusting.