update from 16 months ago: started asking every supplier for water content and about half now include it
#coa-reading 2025-12-03
Wednesday40 messages8 participantstimes are UTC
Highlights from this day
- underfill_uma — quick one the retention time on this one is different from the last lot, problem 18:53
- karl_fischer — i asked BCH for the method and they sent it. that alone put them ahead of most 19:24
- acetate_ash — retention time shifts between runs are normal. relative retention time is the number to compare 19:33
- gus_charts — while im here if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not 20:20
- gus_charts — sorry to jump in the paperwork can be perfect and the vial can still be light. weigh it the three way match is vial, certificate, invoice. if all three agree you have… 21:05
one decimal versus two is usually just house style, not precision
mixed fonts and inconsistent kerning in one document is worth a second look
single wavelength detection can miss a co-eluting impurity that does not absorb there
is water content normally on a certificate or do you have to ask
thats a tell
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 / 10mgquick one the retention time on this one is different from the last lot, problem
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is endotoxin ever tested on research material
tfa or acetate, how do i tell from the paperwork
ask for water content
weigh the vial
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i asked BCH for the method and they sent it. that alone put them ahead of most
retention time shifts between runs are normal. relative retention time is the number to compare
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not detected means nothing
looks re-dated
whats the related substances table actually telling me
how do you verify a certificate is actually from the lab it says
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i have never seen a research certificate with an endotoxin result on it. not once
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial, still working it out
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
does anyone keep a folder of certificates to compare over time
good certificate actually
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
while im here if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
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a certificate should name the method, the instrument, the column and the operator. most name none of those
is there a standard layout or does every lab do their own
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
sloppy not sinister
sorry to jump in the paperwork can be perfect and the vial can still be light. weigh it
the three way match is vial, certificate, invoice. if all three agree you have something
slightly off topic but does anyone actually check the residual solvents section
two certificates from the same supplier have an identical chromatogram, is that normal
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, ill dig out the number
is area percent the same thing as how many mg are in the vial
if you only read one line on a certificate, read the lot number. if you read two, read the assay
*Janoshik not the other one
thats the counterion
ok so the three way match is vial, certificate, invoice. if all three agree you have something
purity is not assay