does anyone keep a folder of certificates to compare over time
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#coa-reading 2026-01-10
Saturday22 messages7 participantstimes are UTC
Highlights from this day
- split_dose_sam — if you only read one line on a certificate, read the lot number. if you read two, read the assay 21:22
- hk_hplc — the three way match is vial, certificate, invoice. if all three agree you have something 21:58
- ghent_gradient — nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself 23:07
if you only read one line on a certificate, read the lot number. if you read two, read the assay
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 / 10mgtfa or acetate, how do i tell from the paperwork
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not detected means nothing
thats the counterion
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
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
one decimal versus two is usually just house style, not precision
is a supplier certificate worth anything on its own
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not, i could be wrong
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
[edited]i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
the three way match is vial, certificate, invoice. if all three agree you have something
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no lot number on this certificate, does that make it worthless
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
sterility and endotoxin are separate tests and almost nobody runs either on research material
genuine question the retention time on this one is different from the last lot, problem
mixed fonts and inconsistent kerning in one document is worth a second look
Batch lookup E-2205: 8 independent reports on file, earliest 2025-09-01.
thats a real table
[edited]single wavelength detection can miss a co-eluting impurity that does not absorb there
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
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