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
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#coa-reading 2025-07-29
Tuesday34 messages7 participantstimes are UTC
Highlights from this day
- peak_split — two certificates from the same supplier have an identical chromatogram, is that normal 20:13
- peak_split — tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 20:18
- peak_split — sorry to jump in no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration 20:30
- void_volume — why would a vial be 99 pure and still assay under label 21:51
while im here net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
what does net peptide content mean next to gross mass
i have never seen a research certificate with an endotoxin result on it. not once
certificate is dated before the lot date, is that just sloppiness
mixed fonts and inconsistent kerning in one document is worth a second look
two certificates from the same supplier have an identical chromatogram, is that normal
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tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
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ok so is endotoxin ever tested on research material
20:27marrow.mod pinned a message
genuine question the font on this one changes halfway down, am i being paranoid
sorry to jump in no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
janoshik-b-0329.pdf
2 pages · 513 KB · not retained in the public archive
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why do some certificates report to one decimal and some to two
how do you verify a certificate is actually from the lab it says
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
the retention time on this one is different from the last lot, problem
update from 4 months ago: started asking every supplier for water content and about half now include it
no lot no certificate
does anyone keep a folder of certificates to compare over time
my 20mg vial weighed more than 40mg of powder, is the certificate lying
a certificate should name the method, the instrument, the column and the operator. most name none of those
| Line | Claims | Does not claim |
|---|---|---|
| Purity (area %) | fraction of detected material that is the target | how many mg are in the vial |
| Assay / content | mg of target per vial | that it is sterile |
| Water content | mass fraction that is water | anything about purity |
| Counterion | salt form and its mass share | net peptide unless stated |
| Related substances | what else was seen | what was not looked for |
check the lot
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
single wavelength detection can miss a co-eluting impurity that does not absorb there
good certificate actually
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genuine question is a supplier certificate worth anything on its own
why would a vial be 99 pure and still assay under label
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i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
coa-b-0329.pdf
1 page · 902 KB · not retained in the public archive
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retention time shifts between runs are normal. relative retention time is the number to compare
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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, anyway
ok so one decimal versus two is usually just house style, not precision
is there a standard layout or does every lab do their own
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
whats the related substances table actually telling me