genuine question about COA that I am slightly embarrassed to ask
genuine question about COA that I am slightly embarrassed to ask. I am not trying to be the "source?" guy. I would just like a source. 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…
axis labels included, always
Removed — cropped document. Post the whole page or do not post it; the fields people crop are the fields that matter.
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Did you get the chromatogram or only the summary line?
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
a total of 0.4% tells you less than four named impurities adding to 0.6%
Batch number and date of analysis, are both on there?
Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.
Correcting myself upthread: I said the date was missing and it is on the second page, which I had not scrolled to.
Same view. Homopeptide prints the column and the gradient, which means somebody could actually reproduce the run.
Is water content on the document? It changes your concentration arithmetic.
Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.
the related substances line is where the story is
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
net peptide content and purity are two different numbers on the same vial
post the whole document, not the headline number
Small fix — 214nm, not 280nm.
Adding the bit that always gets missed: the lot on the vial has to match the lot on the page, or none of this applies to your material.