Verifying a certificate of analysis is a different job from reading it. Reading asks what the numbers mean; verifying asks whether this particular document was issued by the laboratory it names, describes the sample you believe it describes, and can be traced from that sample back to the vial you hold.
A companion guide covers the measurements themselves — identity, chromatographic purity, content. This one stays on provenance, because a well-formatted report with no traceable link to your vial tells you almost nothing, however impressive the percentage at the bottom.
The six things that make a report traceable
| Report or certificate number | A unique identifier the issuing laboratory can look up. A report with no number cannot be confirmed with the laboratory at all. |
|---|---|
| Issuing laboratory | A named organisation with an address or contact route — not just a logo. Note whether it is the seller, the seller's manufacturer, or a third party. |
| Dates | Date received, date tested and date issued are three different dates. A report issued before the lot was made, or years earlier than the vial, is a mismatch. |
| Sample description | What the laboratory says it received: compound name, physical form, quantity. This is the laboratory's words, not the seller's listing. |
| Lot or batch identifier | The identifier must appear both on the report and on the vial label, in the same form. Two similar-looking codes are not a match. |
| Method statement | The analytical method and conditions. Without them, a result is a number without a question attached. |
A verification worksheet you can reuse
Work through these in order and write the answer down, including the answers that are “not shown”. The unknowns are the useful part of the exercise; they are what you would ask a seller about.
- Record the report number exactly as printed, including any prefix.
- Record the issuing laboratory name and whatever contact detail appears on the document.
- Decide, and write down, whether that laboratory is the seller, the manufacturer, or an independent third party. If the document does not say, write “relationship not stated”.
- Copy the lot identifier from the report, then copy it from the vial label separately, and compare the two transcriptions character by character.
- Compare the sample description on the report with the product as listed and as labelled. Note every difference, including quantity and form.
- List the dates in order and check the sequence is possible.
- List each result with the method beside it. Any result with no method goes in an “unsupported” column.
- Note what is not on the report at all — sterility, endotoxin, content as distinct from purity, stability.
- If a contact route exists, ask the laboratory only to confirm that the report number and sample description are theirs. That is a verification question they can answer.
- Date and sign the worksheet, and keep it with the report.
Chain of custody, in plain terms
Chain of custody is the documented sequence of who held the sample, and when, between the container being filled and the analysis being run. Most certificates you will see for research materials do not contain one. That is worth stating plainly rather than assuming: without it, the report describes a sample the laboratory received, and the link from that sample to your specific vial rests on records held elsewhere.
A related gap is sampling. A report typically describes a portion of a lot, not every container in it. How that portion was selected, and by whom, is part of what a chain-of-custody record would tell you.
What verification still cannot establish
Treat the worksheet as a way to make the shape of the evidence visible — what is documented, what is asserted, and what nobody has written down. It is a reasoning tool, not an authenticity guarantee, and no completed worksheet should be described as one. [USP peptide quality resources]