Splitting a vial for two laboratories: how to do it without ruining both — setting out what I have, and where I think it stops being reliable.
Something about splitting a vial 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.
Coming back to post #7, because the follow-up matters more than the original answer.
Repeat determination on the same product line months apart is the measurement that speaks to consistency, and consistency is what most buyers actually want.
Two people can read the same figure differently here and both be reasonable.
On post #23 — agreed on the reasoning, with one qualification.
Cross-checking one lot with two services independently is the cleanest test available and is rarely done because it costs twice as much.
That is the version I use. It may not be the version that is correct.
Blind sampling: submitting without the laboratory or seller knowing the source removes the two easiest ways for a result to be shaped: selective submission and selective reporting. The extra effort is worth it.
If this contradicts something upthread, the upthread version may well be the better one.
Post #41 is the version of this I will quote in future. One addition.
Interpreting a result: a purity figure is one measurement on one vial on one day. Agreement across two services is much stronger. A single high number does not establish a pattern.
Everything in post #50 holds. The case it does not cover is the one I have.
Combining a chromatographic result with a documentation review gives a more complete picture than two chromatographic results, because the failure modes are different.
Someone should write this up properly, and it should probably not be me.
That is a cleaner way of putting what I was circling around.
I changed my mind about splitting a vial after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens.
Read the full topic (71 posts)
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Second pass at: Submitting a sample: the process end to end
Second pass at: Submitting a sample: the process end to end Writing it up because I had to work it out twice and would rather nobody else did. Posting a small dataset on Submitting a sample. It is mine, it is…
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+12 | 16 | 41k | 4mo |
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Revisiting: Aggregate verification data across the directory, with caveats
Revisiting: Aggregate verification data across the directory, with caveats — setting out what I have, and where I think it stops being reliable. I have spent a fortnight trying to pin Aggregate verification…
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+22 | 26 | 23k | 17mo |
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Turnaround times and what they mean for a decision — one year on
On the subject in the title: Turnaround times and what they mean for a decision — one year on Working notes rather than a conclusion. Reading back through what has been written here about Turnaround times,…
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+25 | 29 | 22k | 18mo |
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Chain of custody for a sample you posted yourself — one year on
Posting this under the heading it deserves: Chain of custody for a sample you posted yourself — one year on Everything below is what sits behind that. Posting a small dataset on Chain of custody. It is mine,…
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+28 | 32 | 50k | 15h |
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Chain of custody for a sample you posted yourself
Chain of custody for a sample you posted yourself Writing it up because I had to work it out twice and would rather nobody else did. I was wrong about chain of custody in a thread last spring and I would like…
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2 | 7.3k | 5h |
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Choosing which test to pay for, given a fixed budget
On the subject in the title: Choosing which test to pay for, given a fixed budget Working notes rather than a conclusion. A question about how a record should be read rather than about a supplier. We have…
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+60 | 70 | 49k | 3mo |
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Second pass at: What "verified" means on our vendor pages, stated narrowly
Second pass at: What "verified" means on our vendor pages, stated narrowly — setting out what I have, and where I think it stops being reliable. A question about how a record should be read rather than about…
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+94 | 102 | 20k | 3mo |
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A report I filed that turned out to be wrong, and the correction
A report I filed that turned out to be wrong, and the correction Writing it up because I had to work it out twice and would rather nobody else did. Structured report rather than an opinion, following the…
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+124 | 132 | 12k | 13mo |
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Documenting a supplier's response to a discrepancy — does this still hold?
Documenting a supplier's response to a discrepancy — does this still hold? I have a specific reason for asking rather than idle curiosity, and the context is below. Structured question about turnaround and…
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+47 | 52 | 58k | 16mo |
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About the Independent verification category
Janoshik, Medutest, PeptideMeter and VendorInvestigate results, how to submit a sample, and how to read what comes back. This post is a community wiki: any member at trust level 3 or above can edit it, and…
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+1 | 5 | 5.8k | 23h |