tfa counterion runs higher by mass than acetate. if the certificate does not say, you cannot do the mass balance
#coa-reading 2026-02-07
Saturday52 messages9 participantstimes are UTC
Highlights from this day
- evidence_or_not — nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, we shall see 08:17
- assay_not_purity — a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully 08:23
- evidence_or_not — how do you verify a certificate is actually from the lab it says 09:47
- monoisotopic — i asked QST for the method and they sent it. that alone put them ahead of most 09:54
- tarpit_tam — sterility and endotoxin are separate tests and almost nobody runs either on research material 10:42
coming back after 25 months, has the pinned reading guide changed
weigh the vial
purity is not assay
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thats a real table
| 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 |
what does net peptide content mean next to gross mass
check the lot
ask for water content
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no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
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no lot no certificate
thats the counterion
tfa or acetate, how do i tell from the paperwork
why do some certificates report to one decimal and some to two
is area percent the same thing as how many mg are in the vial
the font on this one changes halfway down, am i being paranoid
i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does
one decimal versus two is usually just house style, not precision
not detected means nothing
whats the minimum a certificate has to have before you take it seriously
certificate is dated before the lot date, is that just sloppiness
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
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
nobody can authenticate a certificate from a scan. you authenticate the material by testing it yourself, we shall see
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is water content normally on a certificate or do you have to ask
test it yourself
the retention time on this one is different from the last lot, problem
sloppy not sinister
coming back to this is sterility tested as part of a normal purity certificate
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
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good certificate actually
two certificates from the same supplier have an identical chromatogram, is that normal
same chromatogram
retention time shifts between runs are normal. relative retention time is the number to compare
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
*that should say weekly
looks re-dated
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net not gross
is a supplier certificate worth anything on its own
why would a vial be 98.6 pure and still assay under label
if you only read one line on a certificate, read the lot number. if you read two, read the assay
thats a tell
whats the related substances table actually telling me
how do you verify a certificate is actually from the lab it says
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no lot number on this certificate, does that make it worthless
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration
not evidence on its own
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i asked QST for the method and they sent it. that alone put them ahead of most
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if the certificate date precedes the lot date, ask. sometimes it is sloppiness and sometimes it is not
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
sterility and endotoxin are separate tests and almost nobody runs either on research material
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a certificate should name the method, the instrument, the column and the operator. most name none of those
follow up gross mass on a jewellery scale plus the water content is enough to catch most underfills, i could be wrong
mixed fonts and inconsistent kerning in one document is worth a second look
i have never seen a research certificate with an endotoxin result on it. not once, ask me again in a month