[Lab] 10th independent test on ERP — 97.2% on a claimed 97.0%, and the trend is the interesting part
10th independent test on ERP — 97.2% on a claimed 97.0%, and the trend is the interesting part. That is the headline. The document, the batch and the service are below so you can argue with the method rather than with me.
To save the first four comments: 97.2% and 97.0%.
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.
Screenshot none of this. Read the whole thread, including the parts where I am told I am wrong.
- ERERP source pageShanghai ERP Biotechnology Co., Ltd. · Shanghai · 90% here, rank 18 · shop at erpbiotechnology.com →
nofollow and sponsored; nobody here is paid for it.best — the order this archive was captured in
Your name and address edited out of the screenshot above. The batch details are untouched and should stay.
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.
post the whole document, not the headline number
post the whole document, not the headline number
Disagree on this specific point. Two honest labs can resolve that impurity differently and report different numbers.
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.
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.
a total of 0.4% tells you less than four named impurities adding to 0.6%
Correcting myself upthread: I said the date was missing and it is on the second page, which I had not scrolled to.
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
chromatogram or it did not happen
a certificate with no method line is decorative
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.
Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently.
the related substances line is where the story is
Area percent or net peptide content? They answer different questions.
Agreed on asking for the storage condition. It is one line and it changes how you read the entire stability claim.
Pushing back a little: a missing field is usually presentation, not concealment. Ask for the full document before drawing conclusions.
net peptide content and purity are two different numbers on the same vial
identity and quantity are two questions and most documents answer one
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.
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.
Asked TFC 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.
- 1Area percent is the peak area of your compound over the total integrated…8 comments in this branch · started by u/teodor_jansen
- 2Net peptide content is the fraction of the powder that is actually peptide…6 comments in this branch · started by u/marisol_frisk