not evidence on its own
#coa-reading 2026-01-28
Wednesday37 messages10 participantstimes are UTC
Highlights from this day
- lisbon_lot — whats the minimum a certificate has to have before you take it seriously 20:48
- lisbon_lot — why do some certificates report to one decimal and some to two 20:56
- maintenance_mo — water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it 21:01
- lisbon_lot — the certificate from JEEP is the one i use to teach this because it actually has a populated impurity table 21:36
- egfr_ed — tfa or acetate, how do i tell from the paperwork 22:14
a certificate should name the method, the instrument, the column and the operator. most name none of those
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
weigh the vial
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
[edited]purity is not assay
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
gross mass on a jewellery scale plus the water content is enough to catch most underfills
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
quick one is sterility tested as part of a normal purity certificate
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check the lot
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whats the minimum a certificate has to have before you take it seriously
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thats a real table
why do some certificates report to one decimal and some to two
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i asked ERP for the method and they sent it. that alone put them ahead of most, we shall see
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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single wavelength detection can miss a co-eluting impurity that does not absorb there, ask me again in a month
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
one decimal versus two is usually just house style, not precision
Digest for the week of 2025-09-12 has been published.
thats the counterion
mixed fonts and inconsistent kerning in one document is worth a second look
the certificate from JEEP is the one i use to teach this because it actually has a populated impurity table
genuine question my 5mg vial weighed more than 10mg of powder, is the certificate lying
certificate is dated before the lot date, is that just sloppiness
no lot no certificate
coming back after 5 months, has the pinned reading guide changed
[edited]genuine question an identical chromatogram on two different lots is the single biggest tell there is
unrelated but what does net peptide content mean next to gross mass
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
tfa or acetate, how do i tell from the paperwork
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
sterility and endotoxin are separate tests and almost nobody runs either on research material
sorry to jump in is endotoxin ever tested on research material
the three way match is vial, certificate, invoice. if all three agree you have something
is a supplier certificate worth anything on its own