the font on this one changes halfway down, am i being paranoid
#coa-reading 2025-08-17
Sunday42 messages7 participantstimes are UTC
Highlights from this day
- salt_bridge — a certificate should name the method, the instrument, the column and the operator. most name none of those, someone check my working 19:24
- salt_bridge — is water content normally on a certificate or do you have to ask 20:28
- u100_pat — what does net peptide content mean next to gross mass 22:03
is area percent the same thing as how many mg are in the vial
thats a tell
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
one decimal versus two is usually just house style, not precision
the retention time on this one is different from the last lot, problem
retention time shifts between runs are normal. relative retention time is the number to compare
an identical chromatogram on two different lots is the single biggest tell there is, ill dig out the number
update from 16 months ago: started asking every supplier for water content and about half now include it
not detected means nothing
the related substances table is the interesting part. a row of "not detected" means they did not look hard, anyway
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, someone check my working
is endotoxin ever tested on research material
same chromatogram
test it yourself
check the lot
gross mass on a jewellery scale plus the water content is enough to catch most underfills, ill dig out the number
good certificate actually
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
thats the counterion
ask for water content
does anyone keep a folder of certificates to compare over time
the three way match is vial, certificate, invoice. if all three agree you have something
residual solvents matter more than people think for anything that went through a lot of purification steps
net not gross
💀9
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
a certificate should name the method, the instrument, the column and the operator. most name none of those, someone check my working
✅13🧊1📈4
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
if you only read one line on a certificate, read the lot number. if you read two, read the assay
[edited]weigh the vial
the certificate from KP is the one i use to teach this because it actually has a populated impurity table
is water content normally on a certificate or do you have to ask
💀17📈4🎉11
is sterility tested as part of a normal purity certificate
single wavelength detection can miss a co-eluting impurity that does not absorb there
my 2mg vial weighed more than 40mg of powder, is the certificate lying
[edited]sterility and endotoxin are separate tests and almost nobody runs either on research material
💀12
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
update on the earlier thing i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
why would a vial be 98.1 pure and still assay under label
for the archive should a certificate say which instrument and method they used
tfa or acetate, how do i tell from the paperwork
what does net peptide content mean next to gross mass
👍15✅2📈7