is sterility tested as part of a normal purity certificate
#coa-reading 2025-07-31
Thursday47 messages9 participantstimes are UTC
Highlights from this day
- lean_mass_lex — does anyone keep a folder of certificates to compare over time 15:26
- bea_reconstitutes — if you only read one line on a certificate, read the lot number. if you read two, read the assay 16:04
- bea_reconstitutes — should a certificate say which instrument and method they used 16:41
- HPLC_Hank — no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration retention time shifts between runs are normal. relative retention time… 18:25
my 2mg vial weighed more than 20mg of powder, is the certificate lying
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, for what its worth
follow up single wavelength detection can miss a co-eluting impurity that does not absorb there
ask for water content
thats the counterion
does anyone keep a folder of certificates to compare over time
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i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
[edited]mixed fonts and inconsistent kerning in one document is worth a second look
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the paperwork can be perfect and the vial can still be light. weigh it
looks re-dated
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the related substances table is the interesting part. a row of "not detected" means they did not look hard
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coming back to this i asked CPC for the method and they sent it. that alone put them ahead of most
if you only read one line on a certificate, read the lot number. if you read two, read the assay
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purity is not assay
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🎉1
update on the earlier thing water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
*VendorInvestigate not the other one
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
why would a vial be 99 pure and still assay under label
should a certificate say which instrument and method they used
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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, happy to be corrected
two certificates from the same supplier have an identical chromatogram, is that normal
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unrelated but a certificate should name the method, the instrument, the column and the operator. most name none of those
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
the three way match is vial, certificate, invoice. if all three agree you have something
*Medutest not the other one
residual solvents matter more than people think for anything that went through a lot of purification steps
how do you verify a certificate is actually from the lab it says
i have never seen a research certificate with an endotoxin result on it. not once, from memory
what does net peptide content mean next to gross mass
one decimal versus two is usually just house style, not precision, thats just me
for the archive no lot number on this certificate, does that make it worthless
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
retention time shifts between runs are normal. relative retention time is the number to compare
sterility and endotoxin are separate tests and almost nobody runs either on research material
the font on this one changes halfway down, am i being paranoid
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update from 22 months ago: started asking every supplier for water content and about half now include it, happy to be corrected
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
retention time shifts between runs are normal. relative retention time is the number to compare
| Line | Claims | Does not claim |
|---|---|---|
| Purity (area %) | fraction of detected material that is the target | how many mg are in the vial |
| Assay / content | mg of target per vial | that it is sterile |
| Water content | mass fraction that is water | anything about purity |
| Counterion | salt form and its mass share | net peptide unless stated |
| Related substances | what else was seen | what was not looked for |
is endotoxin ever tested on research material
check the lot
vial-e-2205-front.png
900 × 1200 · 256 KB · not retained in the public archive
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not evidence on its own
[edited]sloppy not sinister
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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
no lot no certificate
good certificate actually