[Meta] the batch rule is doing its job and people should stop complaining
the batch rule is doing its job and people should stop complaining. Short post, long comment section, probably.
Area percent is the peak area of your compound over the total integrated area, at one wavelength, on one gradient. It is a relative measure of what the detector saw, not a mass fraction of the vial.
UV at 214nm sees the peptide bond and picks up almost everything; at 280nm you are looking at aromatics only. Which wavelength the number came from is part of the number.
Related substances itemised individually is a much stronger document than a single total, because it tells you the shape of the impurity profile rather than its size.
If somebody has the same thing measured a different way, post it next to mine and we will see whether they agree.
best — the order this archive was captured in
The PDF creation date being later than the analysis date is usually a re-issue or a re-export. It is worth one question and it is not evidence of anything on its own.
Disagree that a lower number is automatically worse. A conservative claim that survives testing is worth more than an optimistic one that does not.
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.
the related substances line is where the story is
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
identity and quantity are two questions and most documents answer one
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
Pushing back a little: a missing field is usually presentation, not concealment. Ask for the full document before drawing conclusions.
Pushing back a little: a missing field is usually presentation, not concealment.
Agreed, and the practical version is: ask for the itemised table. If it exists, you get it.
Does the lot on the vial match the lot on the page?
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.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
Correcting myself upthread: I said the date was missing and it is on the second page, which I had not scrolled to.
- 1Net peptide content is the fraction of the powder that is actually peptide…8 comments in this branch · started by u/anders_kuusela