same chromatogram
#coa-reading 2026-02-28
Saturday32 messages6 participantstimes are UTC
Highlights from this day
- per_mg_pete — two certificates from the same supplier have an identical chromatogram, is that normal 12:29
- LC_MS_Lena — i asked GGPeps for the method and they sent it. that alone put them ahead of most 13:19
- peak_split — the certificate from GL Biochem is the one i use to teach this because it actually has a populated impurity table 14:12
- peak_split — a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully water content is why an honest 10mg vial assays at 9.1.… 15:46
two certificates from the same supplier have an identical chromatogram, is that normal
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
whats the related substances table actually telling me
not evidence on its own
why do some certificates report to one decimal and some to two
whats the minimum a certificate has to have before you take it seriously
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the related substances table is the interesting part. a row of "not detected" means they did not look hard
thats the counterion
thats a real table
sorry to jump in how do you verify a certificate is actually from the lab it says
is sterility tested as part of a normal purity certificate
tfa or acetate, how do i tell from the paperwork
i asked GGPeps for the method and they sent it. that alone put them ahead of most
why would a vial be 99 pure and still assay under label
certificate is dated before the lot date, is that just sloppiness
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
residual solvents matter more than people think for anything that went through a lot of purification steps
purity is not assay
is there a standard layout or does every lab do their own
[edited]right so gross mass on a jewellery scale plus the water content is enough to catch most underfills, i could be wrong
the certificate from GL Biochem is the one i use to teach this because it actually has a populated impurity table
net not gross
i have never seen a research certificate with an endotoxin result on it. not once
the three way match is vial, certificate, invoice. if all three agree you have something
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
follow up tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance, i think
thats a tell
sorry to jump in coming back after 9 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
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
test it yourself
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 / 10mgcheck the lot
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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 asked HJ for the method and they sent it. that alone put them ahead of most