What a certificate of analysis is, and is not
A certificate of analysis (COA) is a report issued by a laboratory that tested a specific sample. It states what was submitted, which methods were run, and what those methods measured. It describes one sample from one lot on one date. It is not a general product specification, not a statement about every vial ever sold under that name, and not evidence of any property the report does not list.
The most useful habit when reading a COA is to ask, for every line, which sample, which method, which date. If any of the three is missing, the line cannot be tied to the material a laboratory received.
The sections, in the order they matter
| Section | What it tells you | What to check |
|---|---|---|
| Sample identity | The material name, form, and labeled strength as submitted. | Match the name and strength to the container label exactly, including suffixes such as strength designations. |
| Lot or batch identifier | The specific production lot the sample came from. | The identifier on the report must be the identifier printed on the vial. A report for a neighbouring lot is a different document. |
| Issuing laboratory | Who performed the analysis. | The laboratory is named, the report carries a report or certificate number, and a verification route exists (a portal, a contact, or both). |
| Dates | When the sample was received, analyzed, and reported. | Dates are present and in a sensible order. A report dated before the lot existed cannot describe it. |
| Method | The analytical technique behind each result, for example HPLC for chromatographic purity or mass spectrometry for identity. | Every number has a named method next to it. A percentage with no method is a claim, not a measurement. |
| Reported result | The measured value, with units, qualifiers, and any reporting limit. | Read the value exactly as written. Note whether it is measured, calculated, or a specification the sample was compared against. |
Reading a chromatographic purity result
A result such as "99.59% (HPLC)" means that, under the stated chromatographic conditions, the main peak accounted for that share of the total detected peak area. It is a relative measurement within that method. It does not by itself establish the identity of the main peak, the absence of substances the method cannot detect, water content, residual solvents, sterility, or endotoxin. Those are separate tests with separate lines on a report, or they are absent.
- Identity and purity are different questions. Identity is usually supported by mass-spectrometric data; purity by chromatography.
- Supporting output (a chromatogram, a spectrum) is worth keeping with the record when the laboratory provides it.
- A single high percentage says nothing about any attribute that was not tested.
Verifying the document itself
- Locate the certificate or report number on the document.
- Use the issuing laboratory's verification page or contact route to confirm that number corresponds to the same sample identity, lot, and date.
- Record the verification date alongside the report in the laboratory's internal ledger.
- If the laboratory cannot confirm the number, regard the document as unverified until it can.
Signs that a document needs a question
- The lot on the report does not appear on the vial, or the vial has no lot.
- The same report is presented for more than one strength or product.
- A result has no method, no units, or no date.
- The report cannot be verified with the laboratory that supposedly issued it.
- The document is an image with edited or inconsistent fields.
Each of these is a documentation question to raise with the supplier before relying on the record. Keep the answer with the original document.