What a certificate of analysis is
A certificate of analysis (COA) is the report an analytical laboratory issues for one production lot of a material. It records what was measured, how, on what date, and what the result was. It is not a general statement about a product. A certificate for lot RT20260602 says nothing about lot RT20260710, and a certificate for a 20mg vial says nothing about a 10mg vial filled from a different lot.
For research peptides there are two common kinds. The manufacturer's COA is produced by the synthesis facility's own QC lab as part of releasing the batch. A third-party COA is produced by an independent laboratory that was sent a sample of the finished vial. Neither is automatically better, but they answer different questions: the first asks "did the batch meet the maker's specification", the second asks "what is in the vial a customer receives".
The lines that matter
Lot or batch number
The single most important field. It must match the number printed on the vial label. A certificate with no lot number cannot be tied to anything and should be treated as marketing rather than analysis.
Purity by HPLC
High-performance liquid chromatography separates the sample into its components and measures how much of the UV-absorbing material is the main peak. A result of 99.2% means the main peak was 99.2% of the total peak area at the wavelength used, usually 214 or 220 nm. The remaining 0.8% is mostly related peptide impurities: deletion sequences, oxidised or deamidated forms, and incompletely deprotected species.
What HPLC purity does not measure is anything that does not absorb at that wavelength: water, salts and counter-ions. A 99% HPLC-pure powder is therefore not 99% peptide by weight.
Identity by mass spectrometry
Mass spectrometry confirms that the main peak is the intended molecule by measuring its mass. The certificate should list the theoretical mass and the observed mass, and they should agree to within about a dalton. Retatrutide, for example, has a monoisotopic formula mass near 4731 g/mol. Purity without identity is meaningless: a sample can be 99% pure and be the wrong compound.
Net peptide content
Lyophilised peptide powder contains bound water and counter-ions (usually trifluoroacetate or acetate from purification) as well as the peptide itself. Net peptide content is the fraction of the gross powder mass that is actually peptide, and for TFA salts of peptides it is routinely well below 100%. Many research certificates omit this figure. When it is present, it is the number that determines how much peptide is really in a vial labelled "10mg".
Appearance, water content, endotoxin
Appearance ("white lyophilised powder") is a visual check. Water content by Karl Fischer titration and bacterial endotoxin by LAL assay appear on some certificates and not others. Their absence is normal for a research-grade certificate, but their presence should be read as an extra measurement, not as a sterility claim.
Red flags
- The same purity figure on every product a vendor sells. Real lots vary.
- No lot number, no test date, or no laboratory name.
- A "Pass / Pass / Pass" table with no numeric results and no method listed.
- A test date later than the date the vial shipped.
- A purity figure quoted on a product page with no document behind it.
- A blend reporting a single purity figure. Each component is assayed separately; a blend has a purity per component, not one number.
How Zyrna handles certificates
We are a supplier, not a testing laboratory, and we do not run assays ourselves. Every lot we stock arrives with the manufacturer's certificate, which we forward on request. Where an independent test of a lot we hold exists, it is shown on the product page with its lot number and a link to the document. A purity figure appears on this site only when such a document backs it; otherwise the page says "certificate on request" and nothing more. The full policy is on the quality and handling page.
Every certificate we show carries the laboratory's verification key, and the product page links to the laboratory's own verify page so the document can be checked without taking our word for it. Product pages that currently carry a linked certificate: Retatrutide, Tirzepatide, BPC-157, CJC-1295 with DAC, Tesamorelin, Semax, NAD+, Melanotan II, GHK-Cu and GHK-Cu + BPC-157 + TB-500 + KPV.
Verifying a third-party report yourself
Every third-party certificate on this site carries a verification key printed at the bottom of the report. Take the key from the product page, open the laboratory's verify page (linked beside the key), enter the key, and the laboratory returns its own copy of the report: sample name, batch, results and analysis date. If what the laboratory shows does not match what we show, the laboratory is right and we want to know. This takes about a minute and it is the single strongest check available to a buyer, because it removes the seller from the chain entirely.