if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
#coa-reading 2025-10-17
Friday26 messages7 participantstimes are UTC
Highlights from this day
- sunday_shot — residual solvents matter more than people think for anything that went through a lot of purification steps, ill dig out the number 16:29
- endotoxin_ed — net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial 17:06
- LC_MS_Lena — whats the related substances table actually telling me 17:27
- reading_the_pins — gross mass on a jewellery scale plus the water content is enough to catch most underfills 17:59
the paperwork can be perfect and the vial can still be light. weigh it
residual solvents matter more than people think for anything that went through a lot of purification steps, ill dig out the number
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the related substances table is the interesting part. a row of "not detected" means they did not look hard
[edited]a vial can be 99.4% pure and hold 8.1mg of a 10mg label. both numbers are true and only one of them is the one you care about
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
should a certificate say which instrument and method they used
the retention time on this one is different from the last lot, problem
single wavelength detection can miss a co-eluting impurity that does not absorb there, still working it out
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
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why do some certificates report to one decimal and some to two
thats a real table
tfa or acetate, how do i tell from the paperwork
whats the related substances table actually telling me
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i asked QSC for the method and they sent it. that alone put them ahead of most
whats the minimum a certificate has to have before you take it seriously
does anyone actually check the residual solvents section
the certificate from WWB is the one i use to teach this because it actually has a populated impurity table
check the lot
no lot number on this certificate, does that make it worthless
genuine question nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, thats just me
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
thats the counterion
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists, thats one data point
weigh the vial
gross mass on a jewellery scale plus the water content is enough to catch most underfills
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