i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
#coa-reading 2025-10-28
Tuesday25 messages5 participantstimes are UTC
Highlights from this day
- salt_bridge — for the archive i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does 23:06
- LC_MS_Lena — is a supplier certificate worth anything on its own a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully 23:07
- mg_per_ml — no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, take that with a pinch of salt 23:21
- peak_split — unrelated but two certificates from the same supplier have an identical chromatogram, is that normal sterility and endotoxin are separate tests and almost nobody runs… 23:30
- LC_MS_Lena — coming back after 6 months, has the pinned reading guide changed an identical chromatogram on two different lots is the single biggest tell there is 23:49
purity is not assay
certificate is dated before the lot date, is that just sloppiness
*Janoshik not the other one
for the archive i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
is a supplier certificate worth anything on its own
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
unrelated but retention time shifts between runs are normal. relative retention time is the number to compare
ok so why would a vial be 98.1 pure and still assay under label
update from 9 months ago: started asking every supplier for water content and about half now include it
looks re-dated
is area percent the same thing as how many mg are in the vial
whats the related substances table actually telling me
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, take that with a pinch of salt
for the archive does anyone actually check the residual solvents section
test it yourself
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unrelated but two certificates from the same supplier have an identical chromatogram, is that normal
sterility and endotoxin are separate tests and almost nobody runs either on research material
thats the counterion
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weigh the vial
same chromatogram
net not gross
not detected means nothing
ok so net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
coming back after 6 months, has the pinned reading guide changed
an identical chromatogram on two different lots is the single biggest tell there is
good certificate actually
is water content normally on a certificate or do you have to ask