sterility and endotoxin are separate tests and almost nobody runs either on research material
#coa-reading 2026-02-08
Sunday44 messages10 participantstimes are UTC
Highlights from this day
- peak_split — gross mass on a jewellery scale plus the water content is enough to catch most underfills 22:32
- reship_rita — a certificate should name the method, the instrument, the column and the operator. most name none of those 22:46
- wren_weighs_in — water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it 23:16
- wren_weighs_in — coming back to this does purity by hplc at one wavelength miss things 23:29
my 10mg vial weighed more than 2mg of powder, is the certificate lying
*VendorInvestigate not the other one
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
is a supplier certificate worth anything on its own
mixed fonts and inconsistent kerning in one document is worth a second look
update from 22 months ago: started asking every supplier for water content and about half now include it
is water content normally on a certificate or do you have to ask
gross mass on a jewellery scale plus the water content is enough to catch most underfills
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retention time shifts between runs are normal. relative retention time is the number to compare
the retention time on this one is different from the last lot, problem
should a certificate say which instrument and method they used
the paperwork can be perfect and the vial can still be light. weigh it, anyway
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coming back after 26 months, has the pinned reading guide changed
ok so a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
is area percent the same thing as how many mg are in the vial
slightly off topic but i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
a certificate should name the method, the instrument, the column and the operator. most name none of those
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two certificates from the same supplier have an identical chromatogram, is that normal
a vial can be 99.4% pure and hold 8.1mg of a 10mg label. both numbers are true and only one of them is the one you care about
is endotoxin ever tested on research material
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
residual solvents matter more than people think for anything that went through a lot of purification steps
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, i could be wrong
the related substances table is the interesting part. a row of "not detected" means they did not look hard
22:59quiet.hours pinned a message to this channel
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
net not gross
[edited]unrelated but i asked TFC for the method and they sent it. that alone put them ahead of most, for what its worth
thats a real table
is sterility tested as part of a normal purity certificate
whats the related substances table actually telling me
thats the counterion
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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looks re-dated
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one decimal versus two is usually just house style, not precision
Verification log updated: GGPeps — evidence added, status unchanged.
coming back to this does anyone keep a folder of certificates to compare over time
an identical chromatogram on two different lots is the single biggest tell there is
coming back to this does purity by hplc at one wavelength miss things
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if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
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nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, take that with a pinch of salt
i have never seen a research certificate with an endotoxin result on it. not once
not detected means nothing
ask for water content