97.4 against a certificate of 99.2 is fine. the same supplier landing low four times in a row is a question
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#test-results 2026-05-13
Wednesday39 messages10 participantstimes are UTC
Highlights from this day
- mag_citrate — 97.4 against a certificate of 99.2 is fine. the same supplier landing low four times in a row is a question 16:29
- assay_not_purity — i have never regretted spending the money on a test. i have regretted not testing twice 16:50
- salt_bridge — underfill is more common than impurity. if you only test purity you are testing the less likely failure 22:49
sample handling on your end absolutely affects it. draw cleanly, ship fast, do not let it sit warm, i have it written down somewhere
coming back after 16 months with a follow up result, where do i put it
selection bias
one bad test does not condemn a supplier. one good test does not clear one. both halves get ignored equally
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posting my PeptideMeter result on lot C-4402, what do people make of it
i told QST about a result they would not have liked and they did not argue. credit where it is due
a single sample tells you about a single vial. that is genuinely all it tells you
i had a result i am fairly sure was a handling error on my side and i logged it as such
coming back to this quantity testing is usually a separate line item and it is the one worth paying for
i have never regretted spending the money on a test. i have regretted not testing twice
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weigh the vial before you reconstitute. it costs nothing and catches the common failure
is quantity testing available as a separate thing or bundled
log the lot number
if you are testing to settle an argument you will not settle it with n of 1
thats within range
the honest limits: hobby chain of custody is weak and any result here should be read with that in mind
log the boring results too. a channel that only records failures produces a false picture
do the results in this channel skew because people test when suspicious
i test roughly every tenth vial. it is a sampling strategy, not paranoia
[edited]thats not great
log the boring ones
i had a result i am fairly sure was a handling error on my side and i logged it as such
ok so my read after three years of this: purity is mostly fine across the market and fill consistency is where suppliers differ
a result without a lot number and a purchase date is an anecdote with a pdf attached
when did you buy it
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how do you post a result so it is actually useful to somebody in a year
what interests me is when the gap goes the same direction every time. once is noise, three times is a pattern
Digest for the week of 2025-10-02 has been published.
a supplier disputing a result is rare here and it has never gone well for the supplier
update from 18 months ago: retested the same supplier, result came back better, logged both, happy to be corrected
the widest spread in my data is about 2.6 percentage points across five lots from one supplier, for what its worth
do you test every order or sample it
the results in this channel skew because people test when they are suspicious. that is selection bias and it is real
nice result
my sheet has 5 lots from QSC with a spread under a point, which is tight
post the lot, the purchase month, the lab, the number, and what you were expecting. that makes it useful later
which lab
weigh it first
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underfill is more common than impurity. if you only test purity you are testing the less likely failure
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