unrelated but tfa or acetate, how do i tell from the paperwork
lot-log.csv
858 rows · not retained in the public archive
#coa-reading 2026-03-16
Monday33 messages6 participantstimes are UTC
Highlights from this day
- olive_orders — my 30mg vial weighed more than 15mg of powder, is the certificate lying 15:25
- stack_sceptic — tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 16:28
- peak_split — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, happy to be corrected 18:34
good certificate actually
no lot number on this certificate, does that make it worthless
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
my 30mg vial weighed more than 15mg of powder, is the certificate lying
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the paperwork can be perfect and the vial can still be light. weigh it, i think
what does net peptide content mean next to gross mass
check the lot
gross mass on a jewellery scale plus the water content is enough to catch most underfills
weigh the vial
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the related substances table is the interesting part. a row of "not detected" means they did not look hard
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
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certificate is dated before the lot date, is that just sloppiness
a certificate should name the method, the instrument, the column and the operator. most name none of those
thats a real table
the certificate from GGPeps is the one i use to teach this because it actually has a populated impurity table
[edited]i asked Homopeptide for the method and they sent it. that alone put them ahead of most
net not gross
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
i have never seen a research certificate with an endotoxin result on it. not once
is endotoxin ever tested on research material
residual solvents matter more than people think for anything that went through a lot of purification steps
thats a tell
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does, happy to be corrected
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is area percent the same thing as how many mg are in the vial
is water content normally on a certificate or do you have to ask
not evidence on its own
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the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
retention time shifts between runs are normal. relative retention time is the number to compare, still working it out
does purity by hplc at one wavelength miss things
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an identical chromatogram on two different lots is the single biggest tell there is
if you only read one line on a certificate, read the lot number. if you read two, read the assay
coming back to this one decimal versus two is usually just house style, not precision
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019, someone check my working
test it yourself