tfa or acetate, how do i tell from the paperwork
#coa-reading 2025-01-17
Friday39 messages7 participantstimes are UTC
Highlights from this day
- slow.taper — i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019 14:57
- LC_MS_Lena — is endotoxin ever tested on research material 15:22
- chaser_chris — gross mass on a jewellery scale plus the water content is enough to catch most underfills 15:25
- slow.taper — one decimal versus two is usually just house style, not precision 16:20
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
On this day 4 years ago this channel logged 91 messages.
thats the counterion
thats a tell
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i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
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net not gross
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certificate is dated before the lot date, is that just sloppiness
mixed fonts and inconsistent kerning in one document is worth a second look
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
gross mass on a jewellery scale plus the water content is enough to catch most underfills
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 / 10mgtest it yourself
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
update from 16 months ago: started asking every supplier for water content and about half now include it
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
ok so net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
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one decimal versus two is usually just house style, not precision
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unrelated but no lot number on this certificate, does that make it worthless
is area percent the same thing as how many mg are in the vial
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two certificates from the same supplier have an identical chromatogram, is that normal
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
purity is not assay
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slightly off topic but a certificate should name the method, the instrument, the column and the operator. most name none of those
ask for water content
why do some certificates report to one decimal and some to two
good certificate actually
the font on this one changes halfway down, am i being paranoid
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water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test, we shall see
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check the lot
not detected means nothing
if you only read one line on a certificate, read the lot number. if you read two, read the assay
unrelated but i asked MKM for the method and they sent it. that alone put them ahead of most
same chromatogram
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sterility and endotoxin are separate tests and almost nobody runs either on research material
unrelated but the paperwork can be perfect and the vial can still be light. weigh it, not advice obviously