A Certificate of Analysis, or COA, is the single most important document a research peptide buyer can read. It is the difference between a compound you can trust and one you cannot. This guide explains every field on a COA in plain English, so a qualified researcher can verify exactly what they are sourcing.
Why The COA Matters More Than The Label
Any vendor can print a label. A COA is the independent evidence behind that label. A genuine COA is issued by a third-party laboratory, not the seller, and it ties a specific test result to a specific production lot. If a vendor cannot produce a lot-matched COA from an independent lab, the claimed purity is unverifiable.
The Fields That Matter
Purity Percentage
This is the proportion of the sample that matches the target compound, usually measured by HPLC. A figure such as 98.7 percent means the sample is overwhelmingly the intended sequence with a small remainder of related compounds or process residues. Always check that the purity figure is tied to your specific lot number.
Identity Confirmation
Purity tells you how clean the sample is. Identity tells you whether it is the right compound at all. Identity is typically confirmed by mass spectrometry, which measures the molecular weight of the sample and compares it to the known weight of the target. A COA without identity confirmation tells you the sample is clean but not necessarily correct.
Lot Number
The lot number is what ties everything together. The number on your vial must match the number on the COA. If they do not match, the certificate does not describe what you are holding. Lot-matching is the most commonly skipped verification step and the most important one.
Test Method
The two methods you will see most often are HPLC and mass spectrometry. HPLC, high-performance liquid chromatography, separates the components of a sample to measure purity. Mass spectrometry confirms identity by molecular weight. A strong COA uses both: HPLC for purity, mass spec for identity.
HPLC vs Mass Spec In One Line
HPLC answers the question “how much of this is the right thing?” Mass spectrometry answers the question “is this the right thing at all?” You want both questions answered.
How To Verify Independently
The strongest position a buyer can be in is verifying a COA against a public library. SYNGEN publishes every batch certificate in the COA Library, searchable by compound and lot number, with no login required. That means a researcher can independently confirm a certificate rather than relying on a document handed over privately.
Red Flags
- No lot number, or a lot number that does not match the vial.
- Purity claimed but no test method stated.
- A certificate issued by the seller rather than an independent laboratory.
- No identity confirmation, only a purity figure.
- A COA that cannot be located in any public or verifiable library.