sorry to jump in retention time shifts between runs are normal. relative retention time is the number to compare
[edited]#coa-reading 2025-07-19
Saturday32 messages10 participantstimes are UTC
Highlights from this day
- lisbon_lot — unrelated but a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists 18:58
- evidence_or_not — the font on this one changes halfway down, am i being paranoid purity is what fraction of the contents is the target. assay is how many mg are actually there.… 19:29
- area_percent — quick one update from 17 months ago: started asking every supplier for water content and about half now include it, for what its worth 19:44
- lisbon_lot — tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 20:30
- VialBot — Recon calculator: 30mg in 3ml = 10mg/ml. 20:58
should a certificate say which instrument and method they used
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019, i think
does purity by hplc at one wavelength miss things
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
does anyone keep a folder of certificates to compare over time
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unrelated but a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
an identical chromatogram on two different lots is the single biggest tell there is, ask me again in a month
net not gross
test it yourself
what does net peptide content mean next to gross mass
residual solvents matter more than people think for anything that went through a lot of purification steps
the font on this one changes halfway down, am i being paranoid
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
whats the minimum a certificate has to have before you take it seriously
quick one update from 17 months ago: started asking every supplier for water content and about half now include it, for what its worth
no lot no certificate
thats a real table
thats a tell
same chromatogram
no lot number on this certificate, does that make it worthless
not detected means nothing
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my 30mg vial weighed more than 30mg of powder, is the certificate lying
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
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whats the related substances table actually telling me
Recon calculator: 30mg in 3ml = 10mg/ml.
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
coming back to this one decimal versus two is usually just house style, not precision
how do you verify a certificate is actually from the lab it says
why do some certificates report to one decimal and some to two
looks re-dated
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it, thats just me