why does nobody talk about area percent
why does nobody talk about area percent — that is what I am asking, and I have already read the wiki twice.
Water content 3.8%, acetate 6.2%, purity 99%, net peptide about 90% of label weight. All four numbers honest, and I had to read it twice.
Started keeping a folder of every certificate I have been sent. The ones that itemise impurities are a small group and they are mostly the same suppliers.
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.
Research-use-only material is not approved for human use and nothing here should be read as a recommendation to use it.
best — the order this archive was captured in
Ask what the stability statement was written against — temperature, light, and whether it was the lyophilised powder or the reconstituted solution. Those are three different claims.
a total of 0.4% tells you less than four named impurities adding to 0.6%
a total of 0.4% tells you less than four named impurities adding to 0.6%
Disagree on this specific point. Two honest labs can resolve that impurity differently and report different numbers.
Are the related substances itemised or is it a single total?
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.
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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.
Asked BCH 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.
Left up and flaired Explainer. This is the answer we keep linking, written properly.
Did you get the chromatogram or only the summary line?
post the whole document, not the headline number
Left up and flaired Explainer.
coa_janitor has the distinction right — one is a fraction of the detector signal, the other is a fraction of the mass.
Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.
Pushing back a little: a missing field is usually presentation, not concealment. Ask for the full document before drawing conclusions.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
Agreed — the itemised related substances table is the difference between a document and a receipt.
Is water content on the document? It changes your concentration arithmetic.
Did you ask for the batch-specific document, or is this the catalogue one?
- 1Not quite. Two labs with different gradients can resolve a close-eluting…6 comments in this branch · started by u/ignacio_silva