unrelated but the font on this one changes halfway down, am i being paranoid
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#coa-reading 2026-03-16
Monday33 messages9 participantstimes are UTC
Highlights from this day
- peak_split — filed this one, so what does net peptide content mean next to gross mass, not urgent — and anyone got a checklist they run through before they believe a certificate 15:28
- peak_split — a signature block that is a low resolution graphic on a high resolution document is worth noticing, that is one certificate 15:29
- HPLC_Hank — small thing on this cert a manufacturer certificate is a claim by an interested party. that does not make it false, it makes it a claim, purity, not assay 18:22
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, lot specific not batch. pdf in a folder
[edited]for anyone new to these i keep every certificate as a pdf in a folder by year and it has settled three arguments in two years, karl fischer would settle it
single wavelength detection can miss a co-eluting impurity that does not absorb there, lot specific not batch
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should a certificate say which instrument and method they used
filed this one, so what does net peptide content mean next to gross mass, not urgent — and anyone got a checklist they run through before they believe a certificate
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a signature block that is a low resolution graphic on a high resolution document is worth noticing, that is one certificate
| 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 |
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method and wavelength
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance, the table is where the information is
document question not a chemistry one do people keep certificates as files or just look and move on, or has that changed — and how do i ask for the full batch record without sounding like an inspector
genuine ask i have never seen a research certificate with an endotoxin result on it. not once, ask for the batch record
thats the one, purity and assay differ
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same, re-dated is usually laziness
exactly this
lot, date, method, wavelength
does the wavelength on an rp-hplc purity number actually matter to me
update from 10 months ago: started asking every supplier for water content and about half now include it, lot specific not batch
purity is a fraction of what is there. assay is how much is there. this channel exists because those get swapped, purity, not assay. no lot no certificate
a jpeg of a certificate is not automatically fake and it is automatically harder to check, not detected means the limit. five checks every time
if the certificate and the label disagree, believe neither until somebody explains which is the typo, saved as a pdf. sloppy not sinister
i have seen good certificates from small houses and thin ones from large ones, and the size tells you nothing
size tells you nothing
on net versus gross again water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it, filed by year
Next scheduled reminder for this channel: 5 days, 118 messages since the last one.
ask for method and wavelength first. it is the cheapest question and it sorts most suppliers immediately, karl fischer if you can get it
same chromatogram
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
on net versus gross again is area percent the same thing as how many mg are in the vial
on net versus gross again the certificate from KP is the one i use to teach this because it actually has a populated impurity table
about the date on these no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration. no date, no story
small thing on this cert a manufacturer certificate is a claim by an interested party. that does not make it false, it makes it a claim, purity, not assay
lot bought purity assay/label
A-2418 2025-03 99.1% 9.6 / 10mg
A-2601 2025-08 98.7% 9.8 / 10mg
B-0114 2026-01 99.3% 9.4 / 10mg
B-0329 2026-04 98.9% 9.9 / 10mg👍2✅11🧪1
signed and dated
the impurity table is where the information is. the headline purity is the least interesting number on the page, file it as a pdf