test it yourself
#coa-reading 2025-06-02
Monday29 messages6 participantstimes are UTC
Highlights from this day
- half_life_hal — my 5mg vial weighed more than 15mg of powder, is the certificate lying 18:45
- half_life_hal — i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019 19:03
- tarpit_tam — the certificate from FGP is the one i use to teach this because it actually has a populated impurity table 19:45
- coa_or_cope — single wavelength detection can miss a co-eluting impurity that does not absorb there 20:53
my 5mg vial weighed more than 15mg of powder, is the certificate lying
⚠️11
no lot no certificate
check the lot
right so certificate is dated before the lot date, is that just sloppiness
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully, thats one data point
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
peak RRT area% note
1 0.42 0.31 solvent front
2 0.88 0.44 related substance
3 1.00 98.72 main
4 1.14 0.53 related substancethe paperwork can be perfect and the vial can still be light. weigh it, happy to be corrected
why would a vial be 99.2 pure and still assay under label
❤️1
one decimal versus two is usually just house style, not precision
should a certificate say which instrument and method they used
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
ok so is a supplier certificate worth anything on its own
thats a real table
the certificate from FGP is the one i use to teach this because it actually has a populated impurity table
😂10🤝5💀15
ask for water content
is water content normally on a certificate or do you have to ask
what does net peptide content mean next to gross mass
the related substances table is the interesting part. a row of "not detected" means they did not look hard
i have never seen a research certificate with an endotoxin result on it. not once, n of 1 obviously
no lot number on this certificate, does that make it worthless
residual solvents matter more than people think for anything that went through a lot of purification steps, ask me again in a month
single wavelength detection can miss a co-eluting impurity that does not absorb there
📉14
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
two certificates from the same supplier have an identical chromatogram, is that normal
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
an identical chromatogram on two different lots is the single biggest tell there is
i asked HJ for the method and they sent it. that alone put them ahead of most
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
thats a tell