slightly off topic but single wavelength detection can miss a co-eluting impurity that does not absorb there
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#coa-reading 2025-08-23
Saturday25 messages6 participantstimes are UTC
Highlights from this day
- cat_on_the_tray — slightly off topic but single wavelength detection can miss a co-eluting impurity that does not absorb there 00:23
- mg_per_ml — water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it 00:44
- lisbon_lot — no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration 01:39
- peak_split — is area percent the same thing as how many mg are in the vial 02:48
the retention time on this one is different from the last lot, problem
a certificate should name the method, the instrument, the column and the operator. most name none of those
looks re-dated
is there a standard layout or does every lab do their own
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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no lot number on this certificate, does that make it worthless
thats a tell
how do you verify a certificate is actually from the lab it says
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
if you only read one line on a certificate, read the lot number. if you read two, read the assay
what does net peptide content mean next to gross mass
[edited]no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
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certificate is dated before the lot date, is that just sloppiness
not detected means nothing
the certificate from WXT is the one i use to teach this because it actually has a populated impurity table
same chromatogram
purity is not assay
the three way match is vial, certificate, invoice. if all three agree you have something
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
the related substances table is the interesting part. a row of "not detected" means they did not look hard
is area percent the same thing as how many mg are in the vial
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the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
slightly off topic but should a certificate say which instrument and method they used
is endotoxin ever tested on research material