good certificate actually
#coa-reading 2025-11-16
Sunday39 messages9 participantstimes are UTC
Highlights from this day
- net_peptide — a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully 10:18
- reship_rita — update from 9 months ago: started asking every supplier for water content and about half now include it 11:47
- customs_owl — two certificates from the same supplier have an identical chromatogram, is that normal 15:39
- HPLC_Hank — does purity by hplc at one wavelength miss things 16:20
- HPLC_Hank — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does 16:23
not detected means nothing
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ok so certificate is dated before the lot date, is that just sloppiness
sterility and endotoxin are separate tests and almost nobody runs either on research material
the certificate from WWB is the one i use to teach this because it actually has a populated impurity table
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
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one decimal versus two is usually just house style, not precision
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
my 10mg vial weighed more than 10mg of powder, is the certificate lying
tfa or acetate, how do i tell from the paperwork
fridge-temps.csv
103 rows · not retained in the public archive
test it yourself
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
update from 9 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 substance🙏7
net not gross
weigh the vial
same chromatogram
gross mass on a jewellery scale plus the water content is enough to catch most underfills
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the three way match is vial, certificate, invoice. if all three agree you have something, ill dig out the number
single wavelength detection can miss a co-eluting impurity that does not absorb there
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why do some certificates report to one decimal and some to two
retention time shifts between runs are normal. relative retention time is the number to compare
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
retention time shifts between runs are normal. relative retention time is the number to compare
whats the minimum a certificate has to have before you take it seriously
whats the related substances table actually telling me
the paperwork can be perfect and the vial can still be light. weigh it
Reminder for customs_owl: dose day is today. Set 7 days ago.
no lot no certificate
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 substancetwo certificates from the same supplier have an identical chromatogram, is that normal
looks re-dated
coming back after 13 months, has the pinned reading guide changed
i asked GGPeps for the method and they sent it. that alone put them ahead of most, i could be wrong
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
does purity by hplc at one wavelength miss things
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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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the retention time on this one is different from the last lot, problem
does anyone keep a folder of certificates to compare over time
right so is endotoxin ever tested on research material
lot-log.csv
439 rows · not retained in the public archive
thats the counterion