if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
#coa-reading 2026-03-02
Monday50 messages13 participantstimes are UTC
Highlights from this day
- lena_lots — nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself 17:56
- mood_dip_mari — a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists 18:14
- karl_fischer — single wavelength detection can miss a co-eluting impurity that does not absorb there 20:12
- karl_fischer — i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019 20:35
coming back after 20 months, has the pinned reading guide changed
whats the minimum a certificate has to have before you take it seriously
check the lot
why would a vial be 99.2 pure and still assay under label
i asked FGP for the method and they sent it. that alone put them ahead of most
Testing queue: 8 submissions open, 106 awaiting dispatch.
no lot number on this certificate, does that make it worthless
[redacted at member request] · archive policy
tfa or acetate, how do i tell from the paperwork
no lot no certificate
residual solvents matter more than people think for anything that went through a lot of purification steps
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
*Janoshik not the other one
should a certificate say which instrument and method they used
ask for water content
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
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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update from 7 months ago: started asking every supplier for water content and about half now include it
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thats the counterion
the three way match is vial, certificate, invoice. if all three agree you have something, i think
gross mass on a jewellery scale plus the water content is enough to catch most underfills
[edited]if you only read one line on a certificate, read the lot number. if you read two, read the assay
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certificate is dated before the lot date, is that just sloppiness
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does anyone keep a folder of certificates to compare over time
not evidence on its own
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my 10mg vial weighed more than 5mg of powder, is the certificate lying
same chromatogram
good certificate actually
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
whats the related substances table actually telling me
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
retention time shifts between runs are normal. relative retention time is the number to compare
net not gross
an identical chromatogram on two different lots is the single biggest tell there is
| 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
two certificates from the same supplier have an identical chromatogram, is that normal
is a supplier certificate worth anything on its own
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
is water content normally on a certificate or do you have to ask
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
single wavelength detection can miss a co-eluting impurity that does not absorb there
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water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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
weigh the vial
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
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*PeptideMeter not the other one
is there a standard layout or does every lab do their own