#coa-reading 2025-07-03

Thursday15 messages4 participantstimes are UTC

Highlights from this day

assay_not_purity — for the archive net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial, thats just me 04:24
apnoea_down_two — i asked KP for the method and they sent it. that alone put them ahead of most 05:07
assay_not_purity — while im here the certificate from KP is the one i use to teach this because it actually has a populated impurity table 05:11
pinch_not_stretch — unrelated but tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 06:53
VialBot — New independent result logged — QSC, lot SG-1177, purity 98.6% (Medutest). 06:55

check the lot

a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists

for the archive net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial, thats just me

i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does

the honest summary is that a certificate tells you what the supplier says about a lot they chose to test

purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions

while im here retention time shifts between runs are normal. relative retention time is the number to compare

i asked KP for the method and they sent it. that alone put them ahead of most

should a certificate say which instrument and method they used

while im here the certificate from KP is the one i use to teach this because it actually has a populated impurity table

a certificate should name the method, the instrument, the column and the operator. most name none of those

test it yourself

same chromatogram

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unrelated but tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance

New independent result logged — QSC, lot SG-1177, purity 98.6% (Medutest).

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