A Certificate of Analysis, or COA, is the laboratory's record of what was measured on one specific lot of a compound. For research peptides it is the main document that links the vial in your freezer to its test results. This guide walks through the parts of a typical COA and what each part does and does not tell you.
1. Identification
Look for the product name, the lot (batch) number and, often, the sequence, molecular formula and molecular weight. The lot number on the COA must match the lot number on your vial. If it does not, the COA does not describe your material.
2. Purity by HPLC
High-performance liquid chromatography (HPLC) separates a sample into its components. The COA reports purity as the area of the main peak as a percentage of the area of all peaks, usually read at a UV wavelength near 214 nm, where the peptide bond absorbs. A result of 98% means the main peak makes up 98% of the peak area. It does not mean the vial is 98% peptide by weight, because water and counter-ions such as acetate or TFA are not counted in this measurement.
3. Identity by mass spectrometry
Mass spectrometry measures the mass of the molecules in a sample. The COA lists the expected mass and the observed mass. A close match indicates that the main component is the intended molecule. It speaks to identity, not to quantity.
4. Dates, laboratory and method
Check the test date, the name of the laboratory and the method details, such as the column, the gradient and the detection wavelength. A COA from an independent third-party laboratory adds a layer of verification that an in-house report does not.
5. What a COA does not tell you
Net peptide content (how much of the powder, by weight, is peptide), water content, counter-ion content, endotoxin and sterility are separate tests. If your assay depends on one of them, ask whether it was measured and request the result.
- The lot number matches your vial.
- The purity method is stated.
- The observed mass matches the expected mass.
- The laboratory and the test date are shown.
- The results are specific to your lot.
Questions readers ask
Does a high HPLC purity prove it is the right molecule?
No. Purity and identity are separate questions. Mass spectrometry answers the identity question.
Is purity the same as the amount of peptide in the vial?
No. Purity is a ratio of peak areas. The amount of peptide by weight also depends on water and counter-ions, and is measured by a separate method.
Can I use a COA from a different lot?
No. A COA describes one lot only.
Where is the COA for a product from Alchemy Gold Research?
Open the product page and look under Specifications. If you have a question about the COA for your lot, contact us and include the lot number.
For laboratory research use only. Not for human consumption. Not approved by the FDA for human or veterinary use. This article describes laboratory documents and methods in general terms and is not medical advice.