How to read a certificate of analysis
The certificate of analysis is the only document that speaks about the material in front of you. The data sheet describes what should arrive; the certificate describes what did. When the two disagree, the certificate wins.
First, the lot number
Before reading a single result, check that the lot number on the certificate matches the one on the drum in front of you. It is the most frequent mistake and the most expensive: a flawless certificate from another lot says absolutely nothing about the material you are about to use.
That number is also the thread tying the material to its analysis and to the lot retained sample. Without it, there is no way to check a result later on.
Results, not limits
A valid certificate has two distinct columns: the specification and the result. The specification says «≥ 95 %»; the result says «96.4 %».
When the results column repeats the limits — «complies», «conforms», «≥ 95 %» — you are not reading an analysis, you are reading a cover page. The analysis may well exist, but that document does not prove it, and if your health authority asks tomorrow, it will not prove it then either.
Every result must carry its method beside it. «Curcuminoids 96.4 % (HPLC, USP)» is a result. «Curcuminoids 96.4 %» is half a sentence.
Which sections have to be there
Identity and assay of the marker, with method. Loss on drying and total ash, which speak of moisture and residual mineral. Particle size. Heavy metals — lead, cadmium, mercury, arsenic — as four separate values, not one global «complies». Pesticides and aflatoxins where the matrix demands them. Residual solvents if the process used any organic solvent. And full microbiology: total aerobic count, moulds and yeasts, E. coli, Salmonella.
Plus the administrative data that make the document verifiable: analysis date, manufacturing date, expiry date, the laboratory that ran it and the signature of whoever released the lot.
Signs that something is off
Identical results lot after lot. A real process has variation: if three consecutive certificates say exactly 95.0 %, what you are looking at is probably not a measurement.
Impossible dates: an analysis date earlier than the manufacturing date, or an expiry that does not match the shelf life declared on the sheet.
A method quoted without version or reference. Bare «HPLC» reproduces nothing; «HPLC per USP <621>» does.
And the classic: a PDF certificate with editable fields, or with different typefaces inside the same table.
What to do with it afterwards
File it next to the lot number and the delivery note, and keep it for at least the full shelf life of the finished product that carries it. In an inspection, that is the chain that gets followed.
If your volume justifies it, send one lot in every so many to an independent laboratory. It is not distrust: it is the only way to know whether the variation your supplier declares is the real one, and it is a far easier conversation to have before a problem than after.