my read after three years of this: purity is mostly fine across the market and fill consistency is where suppliers differ
#test-results 2026-03-08
Sunday58 messages11 participantstimes are UTC
Highlights from this day
- LC_MS_Lena — anyone had a result they think was a lab error rather than a bad vial 18:44
- LC_MS_Lena — if you are testing to settle an argument you will not settle it with n of 1 18:50
- endotoxin_ed — one bad test does not condemn a supplier. one good test does not clear one. both halves get ignored equally 19:38
how do you post a result so it is actually useful to somebody in a year
ok so anyone tested the same lot twice at different labs
posting my Janoshik result on lot H-2814, what do people make of it
thats not great
if you are testing to settle an argument you will not settle it with n of 1
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when did you buy it
one data point
do the results in this channel skew because people test when suspicious
log the boring results too. a channel that only records failures produces a false picture
a point or two between the certificate and an independent result is inside what two labs disagree by, not advice obviously
selection bias
post the lot, the purchase month, the lab, the number, and what you were expecting. that makes it useful later
my vial assayed under label but the purity was fine, which matters more
log the boring results too. a channel that only records failures produces a false picture, i think
98.1 against a certificate of 97.4 is fine. the same supplier landing low four times in a row is a question
nice result
assay under label with good purity means you got less of the right thing. that is a fill problem, not a synthesis problem
the widest spread in my data is about 2.6 percentage points across five lots from one supplier
follow up i test roughly every tenth vial. it is a sampling strategy, not paranoia
[edited]is anyone tracking results over time in a way they would share
my read after three years of this: purity is mostly fine across the market and fill consistency is where suppliers differ
what interests me is when the gap goes the same direction every time. once is noise, three times is a pattern
thats within range
quantity testing is usually a separate line item and it is the one worth paying for
thats a fill problem
has a supplier ever disputed a result posted here
whats the worst result anyone has logged and what happened next
whats the underfill rate people are actually seeing
i told QSC about a result they would not have liked and they did not argue. credit where it is due
[edited]does a bad result on one lot condemn the whole supplier
update from 11 months ago: retested the same supplier, result came back better, logged both
a result without a lot number and a purchase date is an anecdote with a pdf attached
unrelated but underfill is more common than impurity. if you only test purity you are testing the less likely failure, ill dig out the number
update from 26 months ago: retested the same supplier, result came back better, logged both
sample handling on your end absolutely affects it. draw cleanly, ship fast, do not let it sit warm
the honest limits: hobby chain of custody is weak and any result here should be read with that in mind
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log the boring ones
is a purity-only test worth the money if underfill is the common failure
how many lots do you need before you can say anything about a supplier
is it worth testing if the vial has already been through a warm transit
coming back after 12 months with a follow up result, where do i put it
[edited]one bad test does not condemn a supplier. one good test does not clear one. both halves get ignored equally, n of 1 obviously
attach the pdf, i have it written down somewhere
weigh the vial before you reconstitute. it costs nothing and catches the common failure
weigh it first
my sheet has 7 lots from GGPeps with a spread under a point, which is tight, thats one data point
a supplier disputing a result is rare here and it has never gone well for the supplier
the honest limits: hobby chain of custody is weak and any result here should be read with that in mind
log the lot number
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test it again
janoshik-b-0329.pdf
2 pages · 543 KB · not retained in the public archive
right so the results in this channel skew because people test when they are suspicious. that is selection bias and it is real
how do you separate batch variance from supplier variance
anyone had a result they think was a lab error rather than a bad vial
lot bought purity assay/label
A-2418 2025-03 99.1% 9.6 / 10mg
A-2601 2025-08 98.7% 9.8 / 10mg
B-0114 2026-01 99.3% 9.4 / 10mg
B-0329 2026-04 98.9% 9.9 / 10mgwhats the lot
a single sample tells you about a single vial. that is genuinely all it tells you
if you are testing to settle an argument you will not settle it with n of 1
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which lab
the widest spread in my data is about 2.6 percentage points across five lots from one supplier
i have never regretted spending the money on a test. i have regretted not testing twice, ask me again in a month
*Medutest not the other one
one bad test does not condemn a supplier. one good test does not clear one. both halves get ignored equally
weights-monthly.csv
234 rows · not retained in the public archive
thats within range