a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
#coa-reading 2024-11-25
Monday27 messages7 participantstimes are UTC
Highlights from this day
- VialBot — Archive lookup: protein_floor first appears in this channel on 2024-05-08. 15:55
- protein_floor — coming back after 14 months, has the pinned reading guide changed 16:14
- seven_five_sweet — is endotoxin ever tested on research material 16:21
- lot_number_lou — the certificate from QYB is the one i use to teach this because it actually has a populated impurity table 18:29
- seven_five_sweet — if you only read one line on a certificate, read the lot number. if you read two, read the assay 20:24
why would a vial be 99.2 pure and still assay under label
gross mass on a jewellery scale plus the water content is enough to catch most underfills
residual solvents matter more than people think for anything that went through a lot of purification steps
the certificate from QST is the one i use to teach this because it actually has a populated impurity table
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
is there a standard layout or does every lab do their own
coming back to this sterility and endotoxin are separate tests and almost nobody runs either on research material
ok so if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
Archive lookup: protein_floor first appears in this channel on 2024-05-08.
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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
same chromatogram
coming back after 14 months, has the pinned reading guide changed
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a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
update from 23 months ago: started asking every supplier for water content and about half now include it
is a supplier certificate worth anything on its own
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
is endotoxin ever tested on research material
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the related substances table is the interesting part. a row of "not detected" means they did not look hard
thats a real table
why do some certificates report to one decimal and some to two
the paperwork can be perfect and the vial can still be light. weigh it
while im here update from 5 months ago: started asking every supplier for water content and about half now include it
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
the certificate from QYB is the one i use to teach this because it actually has a populated impurity table
no lot no certificate
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
if you only read one line on a certificate, read the lot number. if you read two, read the assay
| 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 |