the COA thing finally clicked for me and I want to write it down
the COA thing finally clicked for me and I want to write it down. Making the case below, and I expect to lose some of it in the comments.
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.
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.
LC-MS gives you identity; UV purity gives you a relative quantity. A document with the first and not the second, or the reverse, is answering half the question.
batch number, date of analysis, method, individual impurities — that is the minimum set
The document I was worried about turned out to be a re-issue with a later creation date. Asked, got the original, entirely ordinary.
Did you ask for the batch-specific document, or is this the catalogue one?
Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently.
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.
Your name and address edited out of the screenshot above. The batch details are untouched and should stay.
post the whole document, not the headline number
the related substances line is where the story is
Cosigning. The batch identifier is load-bearing, and a certificate that cannot be tied to the vial in your hand is not about your vial.
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.
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.
Sent one vial to PeptideMeter and VendorInvestigate. 99.4% and a claimed 99.0%. Cost me more than the vial and I would do it again.
Same view. GL Biochem prints the column and the gradient, which means somebody could actually reproduce the run.
Same view.
This is the sentence to take away. The rest of the thread is footnotes to it.
- 1LC-MS gives you identity; UV purity gives you a relative quantity. A…6 comments in this branch · started by u/gastric_emptying_g