why do some certificates report to one decimal and some to two
#coa-reading 2025-11-23
Sunday41 messages7 participantstimes are UTC
Highlights from this day
- maintenance_mo — whats the minimum a certificate has to have before you take it seriously 19:13
- bench_notes — the retention time on this one is different from the last lot, problem 21:33
- bench_notes — tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance 22:11
- bench_notes — the paperwork can be perfect and the vial can still be light. weigh it a certificate should name the method, the instrument, the column and the operator. most name… 22:53
same chromatogram
the font on this one changes halfway down, am i being paranoid
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, n of 1 obviously
i asked SSA for the method and they sent it. that alone put them ahead of most, ill dig out the number
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
good certificate actually
the related substances table is the interesting part. a row of "not detected" means they did not look hard
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mixed fonts and inconsistent kerning in one document is worth a second look
[edited]i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
whats the minimum a certificate has to have before you take it seriously
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the certificate from CPC is the one i use to teach this because it actually has a populated impurity table
a supplier certificate on its own is a starting point, not evidence. that is the whole reason the verification channel exists
net not gross
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if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not, i think
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully, thats one data point
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
test it yourself
thats the counterion
purity is what fraction of the contents is the target. assay is how many mg are actually there. different questions
slightly off topic but retention time shifts between runs are normal. relative retention time is the number to compare, take that with a pinch of salt
why would a vial be 96.8 pure and still assay under label
residual solvents matter more than people think for anything that went through a lot of purification steps
sterility and endotoxin are separate tests and almost nobody runs either on research material
check the lot
weigh the vial
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update from 8 months ago: started asking every supplier for water content and about half now include it
water content is why an honest 10mg vial assays at 9.1. karl fischer titration, and most certificates omit it
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
no lot number on this certificate, does that make it worthless
genuine question what does net peptide content mean next to gross mass
i have never seen a research certificate with an endotoxin result on it. not once
gross mass on a jewellery scale plus the water content is enough to catch most underfills
[edited]not evidence on its own
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the retention time on this one is different from the last lot, problem
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one decimal versus two is usually just house style, not precision
[edited]does anyone actually check the residual solvents section
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
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 / 10mgthe paperwork can be perfect and the vial can still be light. weigh it
a certificate should name the method, the instrument, the column and the operator. most name none of those
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an identical chromatogram on two different lots is the single biggest tell there is