a certificate should name the method, the instrument, the column and the operator. most name none of those, happy to be corrected
#coa-reading 2026-05-28
Thursday41 messages8 participantstimes are UTC
Highlights from this day
- LC_MS_Lena — the font on this one changes halfway down, am i being paranoid 20:42
- LC_MS_Lena — is area percent the same thing as how many mg are in the vial 20:45
- LC_MS_Lena — does anyone keep a folder of certificates to compare over time 20:52
- slow.taper — my 10mg vial weighed more than 2mg of powder, is the certificate lying 21:25
- slow.taper — is sterility tested as part of a normal purity certificate 21:39
why would a vial be 99 pure and still assay under label
the related substances table is the interesting part. a row of "not detected" means they did not look hard
net not gross
thats the counterion
the font on this one changes halfway down, am i being paranoid
coa-f-1330.pdf
1 page · 915 KB · not retained in the public archive
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is area percent the same thing as how many mg are in the vial
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check the lot
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does anyone keep a folder of certificates to compare over time
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ok so purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
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what does net peptide content mean next to gross mass
transit-times.csv
489 rows · not retained in the public archive
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
how do you verify a certificate is actually from the lab it says
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water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
not evidence on its own
should a certificate say which instrument and method they used
coming back after 4 months, has the pinned reading guide changed
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a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully, happy to be corrected
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
i have never seen a research certificate with an endotoxin result on it. not once, not advice obviously
while im here two certificates from the same supplier have an identical chromatogram, is that normal
good certificate actually
my 10mg vial weighed more than 2mg of powder, is the certificate lying
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certificate is dated before the lot date, is that just sloppiness
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
does anyone actually check the residual solvents section
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residual solvents matter more than people think for anything that went through a lot of purification steps, i could be wrong
is sterility tested as part of a normal purity certificate
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Inter-lab diff for lot F-1330: 96.8% vs 99.4%. Within expected range.
the certificate from QST is the one i use to teach this because it actually has a populated impurity table
thats a tell
fridge-thermometer.png
800 × 800 · 84 KB · not retained in the public archive
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
sloppy not sinister
if you only read one line on a certificate, read the lot number. if you read two, read the assay
retention time shifts between runs are normal. relative retention time is the number to compare, ymmv
same chromatogram
test it yourself
looks re-dated
the retention time on this one is different from the last lot, problem
update on the earlier thing an identical chromatogram on two different lots is the single biggest tell there is, ymmv