purity is not assay
#coa-reading 2025-06-10
Tuesday18 messages5 participantstimes are UTC
Highlights from this day
- area_percent — net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial 17:16
- taper_or_not — purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions, still working it out 17:44
- taper_or_not — i asked GL Biochem for the method and they sent it. that alone put them ahead of most i was wrong about this for a year: area percent under-reports nothing, it just… 18:40
- VialBot — Assay note: CPC lot G-0641 reported at 99.4% of label content. 19:12
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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thats the counterion
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions, still working it out
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i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019, i think
i have never seen a research certificate with an endotoxin result on it. not once
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test, i have it written down somewhere
sloppy not sinister
i asked GL Biochem for the method and they sent it. that alone put them ahead of most
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
same chromatogram
not detected means nothing
sterility and endotoxin are separate tests and almost nobody runs either on research material
gross mass on a jewellery scale plus the water content is enough to catch most underfills
check the lot
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Assay note: CPC lot G-0641 reported at 99.4% of label content.
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
looks re-dated
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an identical chromatogram on two different lots is the single biggest tell there is, thats just me