no lot number on this certificate, does that make it worthless
#coa-reading 2026-06-14
Sunday46 messages11 participantstimes are UTC
Highlights from this day
- mira_pins — an identical chromatogram on two different lots is the single biggest tell there is 16:14
- mira_pins — two certificates from the same supplier have an identical chromatogram, is that normal 18:57
- ring_size_down — is endotoxin ever tested on research material 19:01
- VialBot — Purity check: no report on file for lot B-0329. Nothing logged either way. 19:21
[redacted at member request] · archive policy
test it yourself
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
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does purity by hplc at one wavelength miss things
residual solvents matter more than people think for anything that went through a lot of purification steps, for what its worth
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
Reminder set. I will post here in 5 days.
sterility and endotoxin are separate tests and almost nobody runs either on research material
[redacted at member request] · archive policy
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same chromatogram
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gross mass on a jewellery scale plus the water content is enough to catch most underfills
chromatogram-overlay.png
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is a supplier certificate worth anything on its own
for the archive tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
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Testing queue: 2 submissions open, 30 awaiting dispatch.
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sorry to jump in the related substances table is the interesting part. a row of "not detected" means they did not look hard
[edited]whats the minimum a certificate has to have before you take it seriously
check the lot
does anyone keep a folder of certificates to compare over time
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an identical chromatogram on two different lots is the single biggest tell there is
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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
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
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i asked QST for the method and they sent it. that alone put them ahead of most
mixed fonts and inconsistent kerning in one document is worth a second look
the three way match is vial, certificate, invoice. if all three agree you have something, not advice obviously
ok so if you only read one line on a certificate, read the lot number. if you read two, read the assay
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is area percent the same thing as how many mg are in the vial
mixed fonts and inconsistent kerning in one document is worth a second look
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
transit-times.csv
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looks re-dated
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
does anyone actually check the residual solvents section
the retention time on this one is different from the last lot, problem
weigh the vial
ask for water content
two certificates from the same supplier have an identical chromatogram, is that normal
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a certificate should name the method, the instrument, the column and the operator. most name none of those
my 2mg vial weighed more than 30mg of powder, is the certificate lying
is endotoxin ever tested on research material
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
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i have never seen a research certificate with an endotoxin result on it. not once
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
Purity check: no report on file for lot B-0329. Nothing logged either way.
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not detected means nothing
thats a tell
| 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 |
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genuine question should a certificate say which instrument and method they used
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update from 9 months ago: started asking every supplier for water content and about half now include it, anyway
good certificate actually