net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
#coa-reading 2026-04-17
Friday34 messages8 participantstimes are UTC
Highlights from this day
- related_subs — nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, i could be wrong 21:42
- deamidation — no lot number on this certificate, does that make it worthless 22:07
- salt_bridge — no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration 22:44
how do you verify a certificate is actually from the lab it says
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residual solvents matter more than people think for anything that went through a lot of purification steps, take that with a pinch of salt
the related substances table is the interesting part. a row of "not detected" means they did not look hard
i have never seen a research certificate with an endotoxin result on it. not once
test it yourself
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the three way match is vial, certificate, invoice. if all three agree you have something
does purity by hplc at one wavelength miss things
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, we shall see
single wavelength detection can miss a co-eluting impurity that does not absorb there
weigh the vial
does anyone keep a folder of certificates to compare over time
an identical chromatogram on two different lots is the single biggest tell there is
update from 15 months ago: started asking every supplier for water content and about half now include it, i could be wrong
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019, ill dig out the number
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, i could be wrong
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is water content normally on a certificate or do you have to ask
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a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
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not evidence on its own
retention time shifts between runs are normal. relative retention time is the number to compare
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
no lot number on this certificate, does that make it worthless
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not detected means nothing
thats a tell
[edited]purity is not assay
lot-log.csv
197 rows · not retained in the public archive
ask for water content
is there a standard layout or does every lab do their own
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
medutest-report-g-0641.pdf
3 pages · 337 KB · not retained in the public archive
no lot no certificate
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good certificate actually
if you only read one line on a certificate, read the lot number. if you read two, read the assay
is endotoxin ever tested on research material
the certificate from JEEP is the one i use to teach this because it actually has a populated impurity table
thats a real table