update from 8 months ago: started asking every supplier for water content and about half now include it
#coa-reading 2026-06-20
Saturday16 messages3 participantstimes are UTC
Highlights from this day
- chaser_chris — no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration 17:06
- chaser_chris — net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial nobody can authenticate a certificate from a scan. you… 17:17
- chaser_chris — i asked HJ for the method and they sent it. that alone put them ahead of most if the certificate date precedes the lot date, ask. sometimes it is sloppiness and… 17:18
- dexa_or_bia — retention time shifts between runs are normal. relative retention time is the number to compare 17:31
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
🎉7
looks re-dated
🎉4😂7
certificate is dated before the lot date, is that just sloppiness
coming back after 11 months, has the pinned reading guide changed
an identical chromatogram on two different lots is the single biggest tell there is
one decimal versus two is usually just house style, not precision
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
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
i asked HJ for the method and they sent it. that alone put them ahead of most
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
single wavelength detection can miss a co-eluting impurity that does not absorb there
good certificate actually
should a certificate say which instrument and method they used
right so water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it, take that with a pinch of salt
same chromatogram
retention time shifts between runs are normal. relative retention time is the number to compare
| Line | Claims | Does not claim |
|---|---|---|
| Purity (area %) | fraction of detected material that is the target | how many mg are in the vial |
| Assay / content | mg of target per vial | that it is sterile |
| Water content | mass fraction that is water | anything about purity |
| Counterion | salt form and its mass share | net peptide unless stated |
| Related substances | what else was seen | what was not looked for |