Archive lookup: night_pin first appears in this channel on 2025-11-29.
#coa-reading 2026-04-06
Monday54 messages10 participantstimes are UTC
Highlights from this day
an identical chromatogram on two different lots is the single biggest tell there is
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
two certificates from the same supplier have an identical chromatogram, is that normal
net not gross
[edited]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 / 10mgmixed fonts and inconsistent kerning in one document is worth a second look
does purity by hplc at one wavelength miss things
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
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what does net peptide content mean next to gross mass
weigh the vial
good certificate actually
not evidence on its own
sloppy not sinister
i have never seen a research certificate with an endotoxin result on it. not once, not advice obviously
Verification log updated: KP — evidence added, status unchanged.
thats the counterion
is there a standard layout or does every lab do their own
does anyone keep a folder of certificates to compare over time
while im here residual solvents matter more than people think for anything that went through a lot of purification steps
update on the earlier thing coming back after 23 months, has the pinned reading guide changed
is a supplier certificate worth anything on its own
[edited]nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
is area percent the same thing as how many mg are in the vial
why would a vial be 97.4 pure and still assay under label
no lot number on this certificate, does that make it worthless
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same chromatogram
should a certificate say which instrument and method they used
[edited]does anyone actually check the residual solvents section
tfa or acetate, how do i tell from the paperwork
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*VendorInvestigate not the other one
no lot no certificate
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quick one if you only read one line on a certificate, read the lot number. if you read two, read the assay
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the font on this one changes halfway down, am i being paranoid
the three way match is vial, certificate, invoice. if all three agree you have something
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
why do some certificates report to one decimal and some to two
[edited]genuine question is water content normally on a certificate or do you have to ask
not detected means nothing
one decimal versus two is usually just house style, not precision, for what its worth
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certificate is dated before the lot date, is that just sloppiness
[edited]mhra_unlicensedupdate on the earlier thing coming back after 23 months, has the pinned reading guide…
coming back to this i asked GL Biochem for the method and they sent it. that alone put them ahead of most, happy to be corrected
gross mass on a jewellery scale plus the water content is enough to catch most underfills
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
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the retention time on this one is different from the last lot, problem
vial-b-0114-front.png
900 × 1200 · 251 KB · not retained in the public archive
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single wavelength detection can miss a co-eluting impurity that does not absorb there
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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a certificate should name the method, the instrument, the column and the operator. most name none of those
is endotoxin ever tested on research material
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, i could be wrong
thats a real table
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
purity is not assay