One concrete data point for the thread. The four things to check on any report, in order: does it name your batch, who commissioned it, what method was used, and does it report content as well as purity. A report failing any of those is weak evidence regardless of the percentage on it.
Following on from Dr.EndoIndy — and this may be the naive question:
Why two laboratories report different purity for the same batch, and which number to believe?
SleepDoc_PDX said:The four things to check on any report, in order: does it name your batch, who commissioned it, what method was used, and does it report content as…
Adding the part of the answer the thread has not reached. The provenance questions are more useful than the numbers. Does the report name the batch on your vial. Is the date consistent with when that batch existed. Is it addressed to the vendor or to the person who paid for the test. Was the sample taken from general stock or supplied by the vendor. A perfect certificate for a different batch is worth nothing, and vendor-supplied samples are the most common way a genuine report ends up misleading.
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Shop Reference StandardsClosing the loop on my own question.
Purity and content being different measurements was the piece I was missing. The vial was overfilled and pure, which is a very different problem from the one I thought I had.
Dr.SportsMedIN said:The provenance questions are more useful than the numbers.
That is correct as far as it goes, and here is where it stops going. One addition: an unstated method makes a report close to uninterpretable. "99% pure" without the technique, the standard and the conditions is a claim, not a measurement.