ok so one decimal versus two is usually just house style, not precision
#coa-reading 2025-11-15
Saturday24 messages6 participantstimes are UTC
Highlights from this day
- batch_bandit — ok so whats the minimum a certificate has to have before you take it seriously 12:01
- rezept_rolf — i asked SGN for the method and they sent it. that alone put them ahead of most 12:13
- lisbon_lot — the certificate from GGPeps is the one i use to teach this because it actually has a populated impurity table 12:46
- lisbon_lot — coming back after 1 months, has the pinned reading guide changed a lab that reports "greater than 98%" rather than a number is telling you they did not integrate… 13:12
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test, i think
i have never seen a research certificate with an endotoxin result on it. not once
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
is sterility tested as part of a normal purity certificate
ask for water content
is endotoxin ever tested on research material
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
📈1⚠️1
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
the three way match is vial, certificate, invoice. if all three agree you have something
no lot no certificate
thats a tell
ok so whats the minimum a certificate has to have before you take it seriously
| 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 |
i asked SGN for the method and they sent it. that alone put them ahead of most
| 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 |
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
what does net peptide content mean next to gross mass
update from 7 months ago: started asking every supplier for water content and about half now include it
the certificate from GGPeps is the one i use to teach this because it actually has a populated impurity table
sloppy not sinister
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 / 10mgcoming back after 1 months, has the pinned reading guide changed
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
while im here purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions, still working it out
why do some certificates report to one decimal and some to two
does anyone actually check the residual solvents section
while im here is water content normally on a certificate or do you have to ask