A certificate lists results for specific assays performed on a specific sample. Everything not listed was not tested, and the document does not distinguish between a test that was not run and a question that was not asked.
A certificate lists results for specific assays performed on a specific sample. Everything not listed was not tested, and the document does not distinguish between a test that was not run and a question that was not asked.
A high purity figure concerns the proportion of the stated compound. Microbiological contamination is a different assay entirely, and a certificate reporting purity alone is silent on it however impressive the percentage.
Some certificates confirm identity explicitly; others report purity against an assumed identity. Where identity was not independently confirmed, a precise percentage is being reported for something that was taken on trust.
Testing is performed on a portion submitted at some point in the past. The relationship between that portion and the item received depends on sampling practice, storage and time, none of which appear on the document.
What makes up the non-target percentage is usually unreported. For most readers that fraction is the interesting one, and a certificate stating a purity figure without characterising the remainder has answered the easier question.
A certificate is a measurement at a moment. Whether the material holds that specification for months under particular storage conditions is a stability study, which is a different and much longer piece of work.
A laboratory accredited for one technique may perform others outside its accredited scope. The certificate may not distinguish, and the accreditation body publishes the scope for anyone who checks.
List what it tested, then list what it did not. The second list is where the uncertainty lives, and a seller willing to discuss it is giving a reader more than a seller who presents the certificate as a complete answer.
The claims on this page about the tests a certificate omits are usually more informative than the ones it includes can be checked against sources outside this site: