what does net peptide content mean next to gross mass
#coa-reading 2026-05-21
Thursday19 messages7 participantstimes are UTC
Highlights from this day
- assay_not_purity — i asked WXT for the method and they sent it. that alone put them ahead of most nobody can authenticate a certificate from a scan. you authenticate the material by… 20:45
- assay_not_purity — why do some certificates report to one decimal and some to two i keep every certificate in a dated folder and compare them. two suppliers had not changed their… 21:32
- endotoxin_ed — while im here the certificate from GGPeps is the one i use to teach this because it actually has a populated impurity table 21:53
- VialBot — Channel stats, last 30 days: 140 messages from 27 members. 21:58
- gip_glp_gil — water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it, thats one data point 22:35
i asked WXT for the method and they sent it. that alone put them ahead of most
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
purity is not assay
a vial can be 99.4% pure and hold 8.1mg of a 10mg label. both numbers are true and only one of them is the one you care about
is sterility tested as part of a normal purity certificate
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
why do some certificates report to one decimal and some to two
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
📉3
the paperwork can be perfect and the vial can still be light. weigh it
the three way match is vial, certificate, invoice. if all three agree you have something
my 2mg vial weighed more than 5mg of powder, is the certificate lying
if you only read one line on a certificate, read the lot number. if you read two, read the assay
while im here the certificate from GGPeps is the one i use to teach this because it actually has a populated impurity table
thats a real table
Channel stats, last 30 days: 140 messages from 27 members.
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
[edited]why would a vial be 98.6 pure and still assay under label
[edited]does anyone keep a folder of certificates to compare over time
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it, thats one data point
| 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 |
is endotoxin ever tested on research material