three years of purity threads, summarised so you do not have to read them
three years of purity threads, summarised so you do not have to read them, and I am aware this is a minority view on this board.
The four things a certificate must carry, and what each one is for.
Batch identifier ties the document to your vial; without it the document is about somebody else’s material. Date of analysis tells you when the number was true. Method — column, gradient, wavelength — is what makes the figure reproducible rather than asserted. Individual related substances give you the shape of what else is in there.
Everything beyond those four is welcome. Anything missing from them is a question to ask before you order, and in my experience the answer arrives quickly from the suppliers who have a batch record to draw it from.
Why the same vial can honestly produce three different numbers.
Purity by area percent is relative to what the detector saw on one gradient at one wavelength. Net peptide content subtracts counterion, water and residual solvent. Mass of peptide per vial is net content times fill weight, and fill weight has its own tolerance.
So a document reading 99% purity, 6% acetate and 4% water is describing a vial that is about 90% peptide by mass, and every one of those numbers is honest. The mistake is treating the headline figure as the answer to "how much peptide did I get".
How to ask for a batch record without it turning into a negotiation.
One email, three requests: the batch-specific certificate for lot X, the method line behind it, and the storage condition the stability statement was written against. No preamble, no explanation of why you want it.
What comes back is the signal. A full document with the column and gradient printed on it, inside a day, tells you there is a real quality system behind the operation. That is the test I run before I order from anyone new, and it costs nothing.
Please do not ask me what dose you should be on. I genuinely do not know and neither does anyone else here.
best — the order this archive was captured in
Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for. A 99% pure acetate salt can still be about 85% peptide by mass.
Pushing back a little: a missing field is usually presentation, not concealment. Ask for the full document before drawing conclusions.
Cosigning. The batch identifier is load-bearing, and a certificate that cannot be tied to the vial in your hand is not about your vial.
Asked for the storage condition behind the stability statement. Got it in a sentence. It is a two-line email and almost nobody sends it.
the counterion is part of the mass you paid for
ask for the storage condition the stability statement was written against
net peptide content and purity are two different numbers on the same vial
Does the lot on the vial match the lot on the page?
batch number, date of analysis, method, individual impurities — that is the minimum set
Correcting myself upthread: I said the date was missing and it is on the second page, which I had not scrolled to.
Yes — and the reason to ask for the whole page is that the interesting parts are the ones people crop out to fit a screenshot.
Did you ask for the batch-specific document, or is this the catalogue one?
Asked JEEP for the batch-specific certificate and had the full document — batch, date, method line naming the column — inside six hours. That is now my baseline for everybody.
My first certificate had a compound name, a percentage and a logo. I thought that was normal. It is not, and now I know what to ask for.
The document I was worried about turned out to be a re-issue with a later creation date. Asked, got the original, entirely ordinary.
a total of 0.4% tells you less than four named impurities adding to 0.6%
- 1Cosigning. The batch identifier is load-bearing, and a certificate that…14 comments in this branch · started by u/ismael_eriksen