Verified here means specific lots were independently measured on stated dates by named services and the results were consistent with the documentation. It is narrower than people assume and deliberately so. Old habit: I write down the expected answer before I calculate it.
What a documentation review can and cannot tell you — that is the question, and I have not found it answered plainly anywhere I have looked.
Something about documentation review does not reconcile and I would like a second pair of eyes before I decide which half is wrong.
Two sources, both reputable, giving figures that cannot both be right unless they are measuring different quantities. My suspicion is that they are, and I cannot see how.
The opening post describes the usual case. This is about the unusual one.
I would call the community position on documentation review likely rather than established, and I would be comfortable defending that hedge.
Verified here means specific lots were independently measured on stated dates by named services and the results were consistent with the documentation. It is narrower than people assume and deliberately so.
Old habit: I write down the expected answer before I calculate it.
The arithmetic in post #3 is right; the assumption feeding it is the part to check.
Practical answer on documentation review, since the theoretical one is upthread: do the simplest check first, write down the result, and only then decide whether the complicated explanation is needed. It usually is not.
It does not extend to lots nobody has seen, it is not a recommendation, and it says nothing about anything other than what was measured.
I have separated what I observed from what I concluded, which does not always happen.
What a supplier does when asked is itself information, and it is information that a chromatogram cannot provide.
VendorInvestigate: documentation and supplier-practice review. Reviews paperwork rather than vials. Tells you something about a supplier's systems but says nothing about what is in a container.
I would want to see it done twice before believing it once.
Combining a chromatographic result with a documentation review gives a more complete picture than two chromatographic results, because the failure modes are different.
Everything in post #9 holds. The case it does not cover is the one I have.
Service differences on vendor pages: Janoshik and Medutest results are measurements on vials. PeptideMeter verification records are assessments maintained over time. VendorInvestigate reviews are documentation assessments. We cite all four because they answer different questions.
I have kept the units in throughout, for the obvious reason.
That matches what I have seen, for whatever a single anecdote is worth.
I read post #14 twice before replying, because I had assumed the opposite.
Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method.
Worth one more sentence than it usually gets.
I would be cautious about generalising from the documentation review example above. It is a good example. It is one example.
Taking post #17 at face value and following it one step further.
A record with four results over sixteen months is a thin record rather than a bad one, and the honest description says which.
That is a description of practice, not a recommendation of it.
One caution on documentation review: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
The version of documentation review that I was taught turned out to be a teaching simplification. Useful, and not true in the way I had assumed it was.
Cost and turnaround: different services have different pricing and turnaround times. Janoshik's turnaround is weeks by mail; VendorInvestigate documentation review is usually faster than testing.
Worth separating two things that post #20 runs together.
The record shows what was measured. Everything beyond that is inference and this site tries to keep the line visible.
Whatever the answer on documentation review turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, invite the correction.
Picking up post #26: that is the part I would want checked first.
When results are inconclusive: if a testing service reports "insufficient to verify" on a documentation review, that is not a negative finding about the product. It means the documents did not contain enough to check.
Post #26 is the version of this I will quote in future. One addition.
The four services answer different questions. A documentation review cannot tell you what is in a vial and a purity assay cannot tell you whether the records are internally consistent.
Where I part company with post #29, and it is a narrow parting.
Medutest: combined purity and identity reporting. Appears throughout vendor documentation. Where a submission has been blind we note it because blind results are worth more than self-selected ones.
Take it as a starting point and not as a specification.