does anyone keep a folder of certificates to compare over time
#coa-reading 2025-08-29
Friday20 messages4 participantstimes are UTC
Highlights from this day
- salt_bridge — no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, i have it written down somewhere 22:04
- vialkeeper — the certificate from SGN is the one i use to teach this because it actually has a populated impurity table, i have it written down somewhere 22:06
- HPLC_Hank — a certificate should name the method, the instrument, the column and the operator. most name none of those 23:01
- HPLC_Hank — i was wrong about this for a year: area percent under-reports nothing, it just answers a different question than assay does 23:04
no lot number, no certificate. a document you cannot tie to the vial in your hand is decoration, i have it written down somewhere
peptidemeter-summary-b-0329.pdf
2 pages · 250 KB · not retained in the public archive
the certificate from SGN is the one i use to teach this because it actually has a populated impurity table, i have it written down somewhere
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how do you verify a certificate is actually from the lab it says
whats the related substances table actually telling me
purity is not assay
the font on this one changes halfway down, am i being paranoid
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
what does net peptide content mean next to gross mass
if you only read one line on a certificate, read the lot number. if you read two, read the assay
residual solvents matter more than people think for anything that went through a lot of purification steps, from memory
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 one decimal versus two is usually just house style, not precision
coming back after 2 months, has the pinned reading guide changed
slightly off topic but mixed fonts and inconsistent kerning in one document is worth a second look
the honest summary is that a certificate tells you what the supplier says about a lot they chose to test
looks re-dated
a certificate should name the method, the instrument, the column and the operator. most name none of those
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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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weigh the vial
| 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 |
should a certificate say which instrument and method they used