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
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#coa-reading 2025-02-09
Sunday46 messages11 participantstimes are UTC
Highlights from this day
- nhs_pathway_nell — 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… 22:18
- step_one_sian — 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 22:37
- residual_solvent — quick one is a supplier certificate worth anything on its own 22:54
- HPLC_Hank — whats the minimum a certificate has to have before you take it seriously 23:13
- igf_one_ivy — should a certificate say which instrument and method they used 23:37
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
sloppy not sinister
no lot number on this certificate, does that make it worthless
whats the related substances table actually telling me
while im here net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
Digest for the week of 2024-09-03 has been published.
for the archive a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully, thats one data point
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
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
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looks re-dated
thats a real table
[edited]purity is not assay
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my 40mg vial weighed more than 2mg of powder, is the certificate lying
slightly off topic but if you only read one line on a certificate, read the lot number. if you read two, read the assay
how do you verify a certificate is actually from the lab it says
if you only read one line on a certificate, read the lot number. if you read two, read the assay
an identical chromatogram on two different lots is the single biggest tell there is
same chromatogram
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quick one is a supplier certificate worth anything on its own
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i asked KP for the method and they sent it. that alone put them ahead of most, from memory
follow up the certificate from FGP is the one i use to teach this because it actually has a populated impurity table
update from 18 months ago: started asking every supplier for water content and about half now include it
sterility and endotoxin are separate tests and almost nobody runs either on research material
the related substances table is the interesting part. a row of "not detected" means they did not look hard
a certificate should name the method, the instrument, the column and the operator. most name none of those
two certificates from the same supplier have an identical chromatogram, is that normal
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
an identical chromatogram on two different lots is the single biggest tell there is
is area percent the same thing as how many mg are in the vial
for the archive the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
one decimal versus two is usually just house style, not precision
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does purity by hplc at one wavelength miss things
whats the minimum a certificate has to have before you take it seriously
| 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 |
net not gross
is endotoxin ever tested on research material
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if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
not detected means nothing
retention time shifts between runs are normal. relative retention time is the number to compare
is water content normally on a certificate or do you have to ask
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ask for water content
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i have never seen a research certificate with an endotoxin result on it. not once
good certificate actually
the three way match is vial, certificate, invoice. if all three agree you have something
should a certificate say which instrument and method they used
| 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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check the lot
update from 2 months ago: started asking every supplier for water content and about half now include it
an identical chromatogram on two different lots is the single biggest tell there is
gross mass on a jewellery scale plus the water content is enough to catch most underfills
weigh the vial
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