[Lab] 12th independent test on QST — 98.6% on a claimed 98.5%, and the trend is the interesting part
12th independent test on QST — 98.6% on a claimed 98.5%, and the trend is the interesting part. One vial, one service, one member paying, which is the only kind of result this board should treat as evidence.
Hard numbers: 98.6% and 98.5%. Anything softer than that is flagged as an impression.
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.
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 analysis tells you when the number was true. Method — column, gradient, wavelength — is what makes the figure reproducible rather than asserted. Individual related substances give you the shape of what else is in there.
Everything beyond those four is welcome. Anything missing from them is a question to ask before you order, and in my experience the answer arrives quickly from the suppliers who have a batch record to draw it from.
That is everything I have. The rest is opinion and I have tried to keep it out.
- QSQST source pageQingdao Saber Technology Pharmaceutical · Qingdao · 94% here, rank 9 · shop at qingdaosabertechnology.com →
nofollow and sponsored; nobody here is paid for it.best — the order this archive was captured in
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.
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.
Are the related substances itemised or is it a single total?
area% is not mass%, and the difference is the whole game
Asked Homopeptide 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.
the related substances line is where the story is
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.
Does the lot on the vial match the lot on the page?
water content is on there and everyone skips 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.
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.
What does the method line actually say? Not the technique — the column and the gradient.
Area percent or net peptide content? They answer different questions.
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.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
Did you ask for the batch-specific document, or is this the catalogue one?
Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
- 1Related substances itemised individually is a much stronger document than a…10 comments in this branch · started by u/freya_baptista