no lot number on this certificate, does that make it worthless
#coa-reading 2025-07-12
Saturday31 messages8 participantstimes are UTC
Highlights from this day
- point_two_five — i asked GGPeps for the method and they sent it. that alone put them ahead of most 12:36
- LC_MS_Lena — quick one update from 16 months ago: started asking every supplier for water content and about half now include it 15:02
- chlorhex — if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not 15:46
- identity_shift — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does 16:30
i have never seen a research certificate with an endotoxin result on it. not once
tfa or acetate, how do i tell from the paperwork
the retention time on this one is different from the last lot, problem
is there a standard layout or does every lab do their own
residual solvents matter more than people think for anything that went through a lot of purification steps
certificate is dated before the lot date, is that just sloppiness
ask for water content
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
retention time shifts between runs are normal. relative retention time is the number to compare
the certificate from WXT is the one i use to teach this because it actually has a populated impurity table, thats one data point
not evidence on its own
[edited]follow up purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
i asked GGPeps for the method and they sent it. that alone put them ahead of most
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Channel stats, last 30 days: 62 messages from 53 members.
does anyone keep a folder of certificates to compare over time
the three way match is vial, certificate, invoice. if all three agree you have something
On this day 6 years ago this channel logged 68 messages.
is endotoxin ever tested on research material
net peptide is gross mass minus water minus counterion. that is why 11.4mg of powder can be a correct 10mg vial
quick one update from 16 months ago: started asking every supplier for water content and about half now include it
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nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself
if you only read one line on a certificate, read the lot number. if you read two, read the assay
coming back after 22 months, has the pinned reading guide changed
does anyone actually check the residual solvents section
if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
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the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
coming back to this 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
right so i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019, we shall see
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration