not evidence on its own
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#coa-reading 2026-01-29
Thursday55 messages10 participantstimes are UTC
Highlights from this day
- coa_or_cope — mixed fonts and inconsistent kerning in one document is worth a second look 19:09
- coa_or_cope — water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it 19:19
- non_scale_win — slightly off topic but the certificate from CPC is the one i use to teach this because it actually has a populated impurity table 20:25
- cass_cagri — tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 22:12
thats a tell
retention time shifts between runs are normal. relative retention time is the number to compare
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
sterility and endotoxin are separate tests and almost nobody runs either 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
an identical chromatogram on two different lots is the single biggest tell there is, thats just me
the related substances table is the interesting part. a row of "not detected" means they did not look hard
update from 16 months ago: started asking every supplier for water content and about half now include it
for the archive gross mass on a jewellery scale plus the water content is enough to catch most underfills
the three way match is vial, certificate, invoice. if all three agree you have something
no lot number on this certificate, does that make it worthless
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, take that with a pinch of salt
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is endotoxin ever tested on research material
not detected means nothing
good certificate actually
ok so nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
power_cut_piathe three way match is vial, certificate, invoice. if all three agree you have something
quick one what does net peptide content mean next to gross mass
should a certificate say which instrument and method they used
check the lot
mixed fonts and inconsistent kerning in one document is worth a second look
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ask for water content
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 no certificate
why would a vial be 98.6 pure and still assay under label
residual solvents matter more than people think for anything that went through a lot of purification steps
i have never seen a research certificate with an endotoxin result on it. not once
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a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully, we shall see
sloppy not sinister
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
genuine question the retention time on this one is different from the last lot, problem
the font on this one changes halfway down, am i being paranoid
is a supplier certificate worth anything on its own
one decimal versus two is usually just house style, not precision
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slightly off topic but the certificate from CPC is the one i use to teach this because it actually has a populated impurity table
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does anyone actually check the residual solvents section
how do you verify a certificate is actually from the lab it says
i asked QST for the method and they sent it. that alone put them ahead of most
whats the minimum a certificate has to have before you take it seriously
purity is not assay
test it yourself
my 30mg vial weighed more than 40mg of powder, is the certificate lying
thats the counterion
[edited]slightly off topic but is sterility tested as part of a normal purity certificate
same chromatogram
net not gross
two certificates from the same supplier have an identical chromatogram, is that normal
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
weigh the vial
if you only read one line on a certificate, read the lot number. if you read two, read the assay
i asked KP for the method and they sent it. that alone put them ahead of most
thats a real table
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
does anyone keep a folder of certificates to compare over time
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tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
lot bought purity assay/label
A-2418 2025-03 99.1% 9.6 / 10mg
A-2601 2025-08 98.7% 9.8 / 10mg
B-0114 2026-01 99.3% 9.4 / 10mg
B-0329 2026-04 98.9% 9.9 / 10mg🧊17