test it yourself
#coa-reading 2025-09-14
Sunday48 messages9 participantstimes are UTC
Highlights from this day
- eat_more_please — a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully 19:46
- lisbon_lot — is water content normally on a certificate or do you have to ask 20:29
- lisbon_lot — the related substances table is the interesting part. a row of "not detected" means they did not look hard 20:38
- net_peptide — one decimal versus two is usually just house style, not precision 21:11
- cold_chain_cmdr — ok so the three way match is vial, certificate, invoice. if all three agree you have something 21:15
tfa or acetate, how do i tell from the paperwork
[edited]water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
is endotoxin ever tested on research material
not evidence on its own
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sterility and endotoxin are separate tests and almost nobody runs either on research material
looks re-dated
[edited]unrelated but a certificate should name the method, the instrument, the column and the operator. most name none of those
genuine question i asked SGN for the method and they sent it. that alone put them ahead of most, anyway
thats a real table
thats the counterion
sorry to jump in purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
for the archive tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
weigh the vial
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
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whats the related substances table actually telling me
the certificate from BCH is the one i use to teach this because it actually has a populated impurity table
does anyone keep a folder of certificates to compare over time
no lot no certificate
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial, your mileage will differ
sloppy not sinister
coming back after 9 months, has the pinned reading guide changed
thats a tell
whats the minimum a certificate has to have before you take it seriously
does purity by hplc at one wavelength miss things
i have never seen a research certificate with an endotoxin result on it. not once
is water content normally on a certificate or do you have to ask
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the related substances table is the interesting part. a row of "not detected" means they did not look hard
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same chromatogram
residual solvents matter more than people think for anything that went through a lot of purification steps
the retention time on this one is different from the last lot, problem
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net not gross
ask for water content
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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unrelated but two certificates from the same supplier have an identical chromatogram, is that normal
one decimal versus two is usually just house style, not precision
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purity is not assay
ok so the three way match is vial, certificate, invoice. if all three agree you have something
medutest-report-b-0329.pdf
3 pages · 369 KB · not retained in the public archive
check the lot
not detected means nothing
if you only read one line on a certificate, read the lot number. if you read two, read the assay
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
update from 17 months ago: started asking every supplier for water content and about half now include it
mixed fonts and inconsistent kerning in one document is worth a second look
how do you verify a certificate is actually from the lab it says
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
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follow up 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
why do some certificates report to one decimal and some to two