[Suspicious] identical chromatogram on two different compounds from the same vendor
identical chromatogram on two different compounds from the same vendor. Order-by-order, with dates, because vibes are not data.
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.
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.
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.
Not medical advice, obviously, and nothing here is approved for human use. One person with a spreadsheet.
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.
the related substances line is where the story is
Your name and address edited out of the screenshot above. The batch details are untouched and should stay.
Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently.
Does the lot on the vial match the lot on the page?
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.
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.
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.
Batch number and date of analysis, are both on there?
Did you ask for the batch-specific document, or is this the catalogue one?
area% is not mass%, and the difference is the whole game
post the whole document, not the headline number
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.
Is water content on the document? It changes your concentration arithmetic.
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.