is area percent the same thing as how many mg are in the vial
💀11👍16🎉13
#coa-reading 2025-10-06
Monday39 messages8 participantstimes are UTC
Highlights from this day
- identity_shift — is area percent the same thing as how many mg are in the vial 20:51
- identity_shift — i asked WWB for the method and they sent it. that alone put them ahead of most 20:55
- gradient_greg — retention time shifts between runs are normal. relative retention time is the number to compare 21:05
- assay_not_purity — one decimal versus two is usually just house style, not precision the three way match is vial, certificate, invoice. if all three agree you have something 22:02
- identity_shift — a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully 23:06
i asked WWB for the method and they sent it. that alone put them ahead of most
🧪15📉7⚠️13
is water content normally on a certificate or do you have to ask
[edited]same chromatogram
🙏3
single wavelength detection can miss a co-eluting impurity that does not absorb there
quick one the three way match is vial, certificate, invoice. if all three agree you have something
retention time shifts between runs are normal. relative retention time is the number to compare
😂2🙏18🎉6
looks re-dated
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
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 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
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
⚠️3
mixed fonts and inconsistent kerning in one document is worth a second look
test it yourself
certificate is dated before the lot date, is that just sloppiness
thats a real table
update from 4 months ago: started asking every supplier for water content and about half now include it, your mileage will differ
the certificate from BCH is the one i use to teach this because it actually has a populated impurity table
does purity by hplc at one wavelength miss things
slightly off topic but i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, ask me again in a month
one decimal versus two is usually just house style, not precision
the three way match is vial, certificate, invoice. if all three agree you have something
📈3⚠️16
the related substances table is the interesting part. a row of "not detected" means they did not look hard
net not gross
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
🎉1
ask for water content
tfa or acetate, how do i tell from the paperwork
Batch lookup B-0114: 9 independent reports on file, earliest 2025-04-23.
weigh the vial
🧊16
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
thats a tell
sorry to jump in my 30mg vial weighed more than 10mg of powder, is the certificate lying
residual solvents matter more than people think for anything that went through a lot of purification steps
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
does anyone keep a folder of certificates to compare over time
thats the counterion
🧪2
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
👀11✅1📈16