is water content normally on a certificate or do you have to ask
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
😂1
#coa-reading 2025-10-25
Saturday53 messages12 participantstimes are UTC
Highlights from this day
- nhs_pathway_nell — update on the earlier thing residual solvents matter more than people think for anything that went through a lot of purification steps 11:02
- void_volume — one decimal versus two is usually just house style, not precision 12:52
- sharps_bin_sid — 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 14:29
- void_volume — mixed fonts and inconsistent kerning in one document is worth a second look, take that with a pinch of salt 15:34
- HPLC_Hank — does anyone actually check the residual solvents section 15:36
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
not detected means nothing
the certificate from CPC is the one i use to teach this because it actually has a populated impurity table
update on the earlier thing residual solvents matter more than people think for anything that went through a lot of purification steps
🤝1💀8🙏1
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
if you only read one line on a certificate, read the lot number. if you read two, read the assay
update from 18 months ago: started asking every supplier for water content and about half now include it
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
weigh the vial
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
sloppy not sinister
ask for water content
single wavelength detection can miss a co-eluting impurity that does not absorb there
[edited]a certificate should name the method, the instrument, the column and the operator. most name none of those
the paperwork can be perfect and the vial can still be light. weigh it
does anyone keep a folder of certificates to compare over time
gross mass on a jewellery scale plus the water content is enough to catch most underfills
ok so purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
one decimal versus two is usually just house style, not precision
coa-b-0329.pdf
1 page · 255 KB · not retained in the public archive
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
why do some certificates report to one decimal and some to two
the three way match is vial, certificate, invoice. if all three agree you have something
right so the related substances table is the interesting part. a row of "not detected" means they did not look hard, ill dig out the number
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
an identical chromatogram on two different lots is the single biggest tell there is
why would a vial be 99.2 pure and still assay under label
certificate is dated before the lot date, is that just sloppiness
quick one retention time shifts between runs are normal. relative retention time is the number to compare
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
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
✅12📉5
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
whats the related substances table actually telling me
[edited]chromatogram-overlay.png
1240 × 720 · 120 KB · not retained in the public archive
i asked JEEP for the method and they sent it. that alone put them ahead of most
sterility and endotoxin are separate tests and almost nobody runs either on research material, happy to be corrected
🔥1
i have never seen a research certificate with an endotoxin result on it. not once
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
right so should a certificate say which instrument and method they used
check the lot
net not gross
good certificate actually
is a supplier certificate worth anything on its own
mixed fonts and inconsistent kerning in one document is worth a second look, take that with a pinch of salt
📉2👍1🎉11
thats the counterion
does anyone actually check the residual solvents section
🧊14👀11
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
purity is not assay
no lot no certificate, not advice obviously
is sterility tested as part of a normal purity certificate
💀4
not evidence on its own
sorry to jump in how do you verify a certificate is actually from the lab it says