anyone tested the same lot twice at different labs
quantity testing is usually a separate line item and it is the one worth paying for
#test-results 2026-05-14
Thursday37 messages10 participantstimes are UTC
Highlights from this day
- salt_bridge — i told Homopeptide about a result they would not have liked and they did not argue. credit where it is due 16:12
- ms_ms_mira — a result without a lot number and a purchase date is an anecdote with a pdf attached 17:16
- ferritin_fay — i test roughly every tenth vial. it is a sampling strategy, not paranoia i told QYB about a result they would not have liked and they did not argue. credit where it… 18:45
my result contradicts the supplier certificate, do i tell them
*PeptideMeter not the other one
thats not great
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
the widest spread in my data is about 2.6 percentage points across five lots from one supplier
my sheet has 8 lots from QYB with a spread under a point, which is tight
assay under label with good purity means you got less of the right thing. that is a fill problem, not a synthesis problem
Inter-lab diff for lot KP-0925: 99% vs 96.8%. Within expected range.
selection bias
does anyone log the negative results, the boring ones
my read after three years of this: purity is mostly fine across the market and fill consistency is where suppliers differ
97.4 against a certificate of 96.8 is fine. the same supplier landing low four times in a row is a question
underfill is more common than impurity. if you only test purity you are testing the less likely failure
sample handling on your end absolutely affects it. draw cleanly, ship fast, do not let it sit warm
i told Homopeptide about a result they would not have liked and they did not argue. credit where it is due
if you are testing to settle an argument you will not settle it with n of 1
Inter-lab diff for lot B-0114: 97.4% vs 99.2%. Within expected range.
has a supplier ever disputed a result posted here
slightly off topic but weigh the vial before you reconstitute. it costs nothing and catches the common failure
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do you test every order or sample it
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test it again
a result without a lot number and a purchase date is an anecdote with a pdf attached
medutest-report-b-0329.pdf
3 pages · 101 KB · not retained in the public archive
what interests me is when the gap goes the same direction every time. once is noise, three times is a pattern
log the boring results too. a channel that only records failures produces a false picture
genuine question whats the underfill rate people are actually seeing
slightly off topic but does a bad result on one lot condemn the whole supplier
a supplier disputing a result is rare here and it has never gone well for the supplier
is quantity testing available as a separate thing or bundled
coming back to this quantity testing is usually a separate line item and it is the one worth paying for
i test roughly every tenth vial. it is a sampling strategy, not paranoia
i told QYB about a result they would not have liked and they did not argue. credit where it is due
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if the vial has been through a bad transit you are testing the transit as much as the supplier
whats the lot
i had a result i am fairly sure was a handling error on my side and i logged it as such
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a single sample tells you about a single vial. that is genuinely all it tells you, anyway
quantity testing is usually a separate line item and it is the one worth paying for
while im here do the results in this channel skew because people test when suspicious