quick one should a certificate say which instrument and method they used
#coa-reading 2025-03-08
Saturday42 messages11 participantstimes are UTC
Highlights from this day
- week_zero — sterility and endotoxin are separate tests and almost nobody runs either on research material 19:45
- week_zero — tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 19:46
- mag_citrate — the related substances table is the interesting part. a row of "not detected" means they did not look hard, someone check my working 22:27
- mag_citrate — does anyone keep a folder of certificates to compare over time 22:41
- tenpence — does anyone actually check the residual solvents section 23:05
residual solvents matter more than people think for anything that went through a lot of purification steps
same chromatogram
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
one decimal versus two is usually just house style, not precision
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why would a vial be 99.4 pure and still assay under label
sterility and endotoxin are separate tests and almost nobody runs either on research material
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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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the three way match is vial, certificate, invoice. if all three agree you have something
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
coming back after 2 months, has the pinned reading guide changed
unrelated but net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial, for what its worth
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
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is water content normally on a certificate or do you have to ask
purity is not assay
while im here update from 22 months ago: started asking every supplier for water content and about half now include it
ask for water content
genuine question if you only read one line on a certificate, read the lot number. if you read two, read the assay
unrelated but why do some certificates report to one decimal and some to two
the related substances table is the interesting part. a row of "not detected" means they did not look hard
not detected means nothing
thats the counterion
thats a tell
fridge-temps.csv
821 rows · not retained in the public archive
no lot no certificate
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what does net peptide content mean next to gross mass
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good certificate actually
coming back to this purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
is sterility tested as part of a normal purity certificate
a certificate should name the method, the instrument, the column and the operator. most name none of those
*PeptideMeter not the other one
sloppy not sinister
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
two certificates from the same supplier have an identical chromatogram, is that normal
test it yourself
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whats the related substances table actually telling me
the related substances table is the interesting part. a row of "not detected" means they did not look hard, someone check my working
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i have never seen a research certificate with an endotoxin result on it. not once
gross mass on a jewellery scale plus the water content is enough to catch most underfills
does anyone keep a folder of certificates to compare over time
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mixed fonts and inconsistent kerning in one document is worth a second look, not advice obviously
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single wavelength detection can miss a co-eluting impurity that does not absorb there
the font on this one changes halfway down, am i being paranoid
does anyone actually check the residual solvents section
| 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 |