two certificates from the same supplier have an identical chromatogram, is that normal
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#coa-reading 2026-01-12
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does anyone keep a folder of certificates to compare over time
Archive lookup: yyz_vial first appears in this channel on 2025-04-13.
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whats the minimum a certificate has to have before you take it seriously
my 40mg vial weighed more than 5mg of powder, is the certificate lying
whats the related substances table actually telling me
what does net peptide content mean next to gross mass
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 / 10mgi was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
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if you only read one line on a certificate, read the lot number. if you read two, read the assay, happy to be corrected
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certificate is dated before the lot date, is that just sloppiness
ok so does purity by hplc at one wavelength miss things
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
ok so the font on this one changes halfway down, am i being paranoid
is water content normally on a certificate or do you have to ask
the certificate from MKM is the one i use to teach this because it actually has a populated impurity table
ask for water content
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purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
how do you verify a certificate is actually from the lab it says
follow up i have never seen a research certificate with an endotoxin result on it. not once
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net not gross
the three way match is vial, certificate, invoice. if all three agree you have something
coming back after 10 months, has the pinned reading guide changed
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tfa or acetate, how do i tell from the paperwork
thats the counterion
same chromatogram
the related substances table is the interesting part. a row of "not detected" means they did not look hard, thats one data point
no lot number on this certificate, does that make it worthless
does anyone actually check the residual solvents section
| 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 |
i asked SGN for the method and they sent it. that alone put them ahead of most
the retention time on this one is different from the last lot, problem
is sterility tested as part of a normal purity certificate
slightly off topic but is area percent the same thing as how many mg are in the vial
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it, ymmv
sterility and endotoxin are separate tests and almost nobody runs either on research material, n of 1 obviously
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not detected means nothing
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
one decimal versus two is usually just house style, not precision
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
not evidence on its own
thats a real table
is there a standard layout or does every lab do their own
medutest-report-sg-1177.pdf
3 pages · 776 KB · not retained in the public archive
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
[edited]a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
purity is not assay
is a supplier certificate worth anything on its own
Recon calculator: 40mg in 2ml = 5mg/ml.
test it yourself
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update from 7 months ago: started asking every supplier for water content and about half now include it