[Question] is 99.1% actually fine or am I being sold a rounding error
is 99.1% actually fine or am I being sold a rounding error. That is the headline. The document, the batch and the service are below so you can argue with the method rather than with me.
Pulling the figures out of the title: 99.1%. All of it is written down as it happened rather than reconstructed.
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.
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.
Screenshot none of this. Read the whole thread, including the parts where I am told I am wrong.
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.
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.
a total of 0.4% tells you less than four named impurities adding to 0.6%
redact your own name, never the batch details
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.
the related substances line is where the story is
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.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.
Are the related substances itemised or is it a single total?
area% is not mass%, and the difference is the whole game
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.
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.
The document I was worried about turned out to be a re-issue with a later creation date. Asked, got the original, entirely ordinary.