a certificate should name the method, the instrument, the column and the operator. most name none of those
#coa-reading 2026-05-24
Sunday28 messages6 participantstimes are UTC
Highlights from this day
- salt_bridge — update from 23 months ago: started asking every supplier for water content and about half now include it 23:04
- underfill_uma — is a supplier certificate worth anything on its own 23:08
- batch_bandit — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, ask me again in a month 23:18
test it yourself
Testing queue: 6 submissions open, 28 awaiting dispatch.
purity is not assay
no lot no certificate
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update from 23 months ago: started asking every supplier for water content and about half now include it
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if you only read one line on a certificate, read the lot number. if you read two, read the assay, thats one data point
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
is a supplier certificate worth anything on its own
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
whats the minimum a certificate has to have before you take it seriously
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
sloppy not sinister
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, ask me again in a month
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for the archive no lot number on this certificate, does that make it worthless
single wavelength detection can miss a co-eluting impurity that does not absorb there, your mileage will differ
retention time shifts between runs are normal. relative retention time is the number to compare
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
same chromatogram
not detected means nothing
the paperwork can be perfect and the vial can still be light. weigh it
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
while im here the font on this one changes halfway down, am i being paranoid
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial, we shall see
net not gross
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
thats a real table