[Vendor] GGPeps vs GL Biochem on the same compound, same month — both cleared 99.0%
Posting this because the title is the whole finding — GGPeps vs GL Biochem on the same compound, same month — both cleared 99.0% — and a number without its method is a rumour.
The numbers the title promised, since a headline without them is worthless: 99.0%. Everything below is context for those.
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.
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.
I will update this if the picture changes rather than quietly leaving it up.
- GLGL Biochem source pageGL Biochem (Shanghai) Ltd. · Shanghai · 91% here, rank 15 · shop at glbiochem.net →
- GGGGPeps source pageNantong Guangyuan Chemical Co., Ltd. · Nantong · 88% here, rank 21 · shop at ggpeps.net →
nofollow and sponsored; nobody here is paid for it.best — the order this archive was captured in
Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.
Batch number and date of analysis, are both on there?
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.
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.
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.
Right, and net peptide content is where the counterion and the water go.
Disagree on this specific point. Two honest labs can resolve that impurity differently and report different numbers.
batch number, date of analysis, method, individual impurities — that is the minimum set
area% is not mass%, and the difference is the whole game
the lot on the vial has to match the lot on the page
Agreed on asking for the storage condition. It is one line and it changes how you read the entire stability claim.
Disagree on this specific point.
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.
Why the same vial can honestly produce three different numbers.
Purity by area percent is relative to what the detector saw on one gradient at one wavelength. Net peptide content subtracts counterion, water and residual solvent. Mass of peptide per vial is net content times fill weight, and fill weight has its own tolerance.
So a document reading 99% purity, 6% acetate and 4% water is describing a vial that is about 90% peptide by mass, and every one of those numbers is honest. The mistake is treating the headline figure as the answer to "how much peptide did I get".
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.
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.
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
Pushing back a little: a missing field is usually presentation, not concealment.
low_appetite_lisa has the distinction right — one is a fraction of the detector signal, the other is a fraction of the mass.
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.
Ask what the stability statement was written against — temperature, light, and whether it was the lyophilised powder or the reconstituted solution. Those are three different claims.
- 1Right, and net peptide content is where the counterion and the water go.…7 comments in this branch · started by u/dario_boateng
- 2Water content 3.8%, acetate 6.2%, purity 99%, net peptide about 90% of label…6 comments in this branch · started by u/karma_irrelevant