What Is a Certificate of Analysis (COA)?
A Certificate of Analysis is the document that tells you what is actually in a peptide vial. Here is what a real COA must contain and how to tell a batch-specific certificate from a marketing flyer.
A Certificate of Analysis is the single document that, if it is real, tells you exactly what is in the vial in front of you. If it is generic or fabricated, it tells you nothing.
This is the short, definitional version of what a COA is, what it should contain, and how to recognize the difference between a batch-specific certificate and a marketing flyer dressed up to look like one. Once you have the definition down, the next step is learning how to read a peptide COA — the full guide with worked examples, verification steps, and supplier comparisons.
For laboratory research use only.
What a COA is
A Certificate of Analysis is a document issued by a chemist — either an in-house analytical team at the supplier or an independent third-party lab — that reports the test results for a specific batch of a product. For a research peptide, the test panel typically includes HPLC purity, retention time, peak area data, and often a mass spectrometry confirmation that the molecular weight matches the labeled compound.
The COA is, in effect, a signed claim. A specific analyst, on a specific date, tested a specific batch using a specific method, and reports a specific result. The signature at the bottom is what turns a printed number into a certificate.
A document that reports a purity number without any of the underlying elements — no batch number, no method, no chromatogram, no analyst — is not a Certificate of Analysis. It is a marketing claim formatted to resemble one.
What a real COA should contain
A legitimate batch-specific peptide COA carries eight elements at minimum: the supplier or lab name, a batch/lot number that matches the vial label, a recent test date, the test method (HPLC, LC-MS, or both), the retention time of the main peak, the peak area data behind the percentage, the calculated purity (typically 95-99%), and the analyst's signature. Missing more than one of them is a signal that the document is generic rather than batch-specific.
The chromatogram — the actual HPLC trace — should also be attached or available on request. The purity percentage is just a calculation derived from the chromatogram; the chromatogram is the source data. A COA that reports a number without the underlying chromatogram is unverifiable.
For the element-by-element checklist with what each line looks like and why it matters, see the full guide on how to read a peptide COA. For a plain-English walkthrough of what HPLC is and how to interpret a chromatogram, see what is HPLC.
Generic vs batch-specific COAs
The most common form of low-quality COA in the research peptide market is the generic product-line COA. It is a real document, often with a real chromatogram, that was produced from one analysis at one point in time — and is then attached to every order of that product regardless of which batch actually shipped.
A generic COA fails the basic test of certifying what is in the specific vial in front of you. The batch number on the document does not match the batch number on the vial. The test date may be a year or more old. The result is statistically plausible but not evidence about the current product.
A batch-specific COA is generated from analysis of the same batch that produced the vial you received. The batch number on the document matches the batch number on the vial. The test date is within the manufacturing window of the current batch. The chromatogram is the actual trace from the lot you are holding.
Three quick checks separate the two forms:
- Does the batch number on the COA match the batch number printed on the vial?
- Is the test date within the last 12 months?
- Is the chromatogram included, and does it show a single dominant peak at the expected retention time?
If the answer to all three is yes, the document is doing its job. If the answer to any of them is no, the document is decorative.
For research use only. Not for human consumption.
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