Archive lookup: HPLC_Hank first appears in this channel on 2024-11-30.
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#coa-reading 2025-04-30
Wednesday25 messages6 participantstimes are UTC
Highlights from this day
- HPLC_Hank — i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019 12:03
- HPLC_Hank — certificate is dated before the lot date, is that just sloppiness 12:06
- mcg_not_mg — purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions 12:47
- non_scale_win — nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself 14:21
- lean_mass_lex — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does 14:29
what does net peptide content mean next to gross mass
a certificate should name the method, the instrument, the column and the operator. most name none of those
tfa or acetate, how do i tell from the paperwork
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
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residual solvents matter more than people think for anything that went through a lot of purification steps
the related substances table is the interesting part. a row of "not detected" means they did not look hard
certificate is dated before the lot date, is that just sloppiness
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my 15mg vial weighed more than 40mg of powder, is the certificate lying
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
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purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
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right so no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
same chromatogram
[edited]mixed fonts and inconsistent kerning in one document is worth a second look
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right so how do you verify a certificate is actually from the lab it says
| 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 |
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
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while im here if you only read one line on a certificate, read the lot number. if you read two, read the assay
update from 21 months ago: started asking every supplier for water content and about half now include it, i think
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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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unrelated but single wavelength detection can miss a co-eluting impurity that does not absorb there, take that with a pinch of salt
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
weigh the vial
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not evidence on its own
thats a real table