PDF producer string says the file was made in a browser. is that normal
PDF producer string says the file was made in a browser. is that normal — a position I have arrived at slowly and would like tested.
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.
Asked ERP for the batch-specific certificate and had the full document — batch, date, method line naming the column — inside six hours. That is now my baseline for everybody.
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.
Sceptical readings welcome. The confident ones are the ones I distrust.
best — the order this archive was captured in
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.
Removed — cropped document. Post the whole page or do not post it; the fields people crop are the fields that matter.
UV at 214nm sees the peptide bond and picks up almost everything; at 280nm you are looking at aromatics only.
Agreed, and the practical version is: ask for the itemised table. If it exists, you get it.
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
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.
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.
I would not read a rounded figure as evasive. Plenty of documents round to one decimal as house style.
This. Area percent answers "what fraction of what the detector saw was the peak I wanted", and people read it as "how much peptide is in the vial".
post the whole document, not the headline 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.
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Are the related substances itemised or is it a single total?
the related substances line is where the story is
Sent one vial to Medutest and VendorInvestigate. 98.1% and a claimed 98.0%. Cost me more than the vial and I would do it again.
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.
How to ask for a batch record without it turning into a negotiation.
One email, three requests: the batch-specific certificate for lot X, the method line behind it, and the storage condition the stability statement was written against. No preamble, no explanation of why you want it.
What comes back is the signal. A full document with the column and gradient printed on it, inside a day, tells you there is a real quality system behind the operation. That is the test I run before I order from anyone new, and it costs nothing.