one decimal versus two is usually just house style, not precision
#coa-reading 2025-09-28
Sunday38 messages9 participantstimes are UTC
Highlights from this day
- endotoxin_ed — right so water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it 19:12
- VialBot — Batch lookup H-2814: 5 independent reports on file, earliest 2025-05-30. 19:22
- retention_time — sorry to jump in i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019 19:32
- tare_weight — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does 20:50
- salt_bridge — whats the related substances table actually telling me 21:05
update on the earlier thing certificate is dated before the lot date, is that just sloppiness
my 10mg vial weighed more than 40mg of powder, is the certificate lying
an identical chromatogram on two different lots is the single biggest tell there is
two certificates from the same supplier have an identical chromatogram, is that normal
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully, ill dig out the number
how do you verify a certificate is actually from the lab it says
check the lot
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right so water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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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
Batch lookup H-2814: 5 independent reports on file, earliest 2025-05-30.
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
residual solvents matter more than people think for anything that went through a lot of purification steps
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test it yourself
sorry to jump in i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
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gross mass on a jewellery scale plus the water content is enough to catch most underfills
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
i have never seen a research certificate with an endotoxin result on it. not once
is water content normally on a certificate or do you have to ask
a certificate should name the method, the instrument, the column and the operator. most name none of those
good certificate actually
weigh the vial
what does net peptide content mean next to gross mass
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tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance, ymmv
no lot no certificate
is sterility tested as part of a normal purity certificate
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
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whats the related substances table actually telling me
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ask for water content
same chromatogram
thats the counterion
the font on this one changes halfway down, am i being paranoid
the related substances table is the interesting part. a row of "not detected" means they did not look hard
is a supplier certificate worth anything on its own
sterility and endotoxin are separate tests and almost nobody runs either on research material
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
single wavelength detection can miss a co-eluting impurity that does not absorb there
retention time shifts between runs are normal. relative retention time is the number to compare