weigh the vial
#coa-reading 2025-03-21
Friday23 messages6 participantstimes are UTC
Highlights from this day
- coa_or_cope — retention time shifts between runs are normal. relative retention time is the number to compare, your mileage will differ an identical chromatogram on two different… 22:49
- endotoxin_ed — sterility and endotoxin are separate tests and almost nobody runs either on research material, ymmv 23:08
- cat_on_the_tray — gross mass on a jewellery scale plus the water content is enough to catch most underfills, ask me again in a month 23:25
two certificates from the same supplier have an identical chromatogram, is that normal
an identical chromatogram on two different lots is the single biggest tell there is, for what its worth
🎉9
good certificate actually
is sterility tested as part of a normal purity certificate
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
whats the minimum a certificate has to have before you take it seriously
quick one why do some certificates report to one decimal and some to two
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
✅1🙏1👍3
ask for water content
🔥4🤝13💀9
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
what does net peptide content mean next to gross mass
[edited]how do you verify a certificate is actually from the lab it says
✅1⚠️4
test it yourself
retention time shifts between runs are normal. relative retention time is the number to compare, your mileage will differ
an identical chromatogram on two different lots is the single biggest tell there is
⚠️12
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
the certificate from KP is the one i use to teach this because it actually has a populated impurity table, for what its worth
is area percent the same thing as how many mg are in the vial
sterility and endotoxin are separate tests and almost nobody runs either on research material, ymmv
⚠️15
looks re-dated
gross mass on a jewellery scale plus the water content is enough to catch most underfills, ask me again in a month
📉10👀13
whats the related substances table actually telling me
not evidence on its own