single wavelength detection can miss a co-eluting impurity that does not absorb there
#coa-reading 2026-03-30
Monday27 messages7 participantstimes are UTC
Highlights from this day
- void_volume — update from 7 months ago: started asking every supplier for water content and about half now include it 21:12
- void_volume — i asked MKM for the method and they sent it. that alone put them ahead of most 21:19
- HPLC_Hank — genuine question the certificate from WXT is the one i use to teach this because it actually has a populated impurity table single wavelength detection can miss a… 21:39
how do you verify a certificate is actually from the lab it says
no lot number on this certificate, does that make it worthless
update from 7 months ago: started asking every supplier for water content and about half now include it
peak RRT area% note
1 0.42 0.31 solvent front
2 0.88 0.44 related substance
3 1.00 98.72 main
4 1.14 0.53 related substancei asked MKM for the method and they sent it. that alone put them ahead of most
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good certificate actually
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is endotoxin ever tested on research material
check the lot
Recon calculator: 20mg in 1.5ml = 10mg/ml.
genuine question the certificate from WXT is the one i use to teach this because it actually has a populated impurity table
single wavelength detection can miss a co-eluting impurity that does not absorb there
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net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
what does net peptide content mean next to gross mass
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follow up one decimal versus two is usually just house style, not precision
the related substances table is the interesting part. a row of "not detected" means they did not look hard
not evidence on its 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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why do some certificates report to one decimal and some to two
sloppy not sinister
same chromatogram
two certificates from the same supplier have an identical chromatogram, is that normal
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looks re-dated
[edited]the three way match is vial, certificate, invoice. if all three agree you have something
ok so a certificate should name the method, the instrument, the column and the operator. most name none of those
should a certificate say which instrument and method they used
not detected means nothing
ok so coming back after 3 months, has the pinned reading guide changed