The arithmetic behind every identity confirmation, worked in full
A peptide has a monoisotopic mass and an average mass, they differ by several daltons at this molecular size, and a certificate that does not say which it quotes cannot be…
Independent testing
Page 22 of 27 of this archive, newest first.
Why a result on one vial says less than the trade needs it to
Chain of custody, in a regulated setting, begins at sampling. Here it begins when the package arrives.
Independent analysis puts a GL Biochem tirzepatide lot at 99.2%, against 95.8% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Pore size, particle size, and why peptides need the wide pores
A shallow gradient resolves impurities that a steep one runs into the parent peak. Both methods are legitimate; only one of them can see the small stuff.
Twelve minutes or forty: what gradient slope buys
We set out the parameters a method disclosure would contain, all of which are known to whoever ran the sample and none of which is commercially sensitive.
Independent analysis puts a SSA orforglipron lot at 95.7%, against 92.2% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
The fourteen-day problem, and what it does to a commercial testing model
Endotoxin is the more tractable of the two questions, and a kinetic chromogenic determination is neither slow nor exotic. It is simply not on the menu.
PeptideMeter result on a Shenzhen semaglutide lot lands 1.9 points below the supplier’s figure
The supplier has not disputed the finding. It has not explained the gap either.
Glass, elastomer, aluminium: a three-material argument about one closure
Particulate matter is the oldest quality attribute in injectable manufacture and the one a private buyer is best placed to assess without instrumentation.
Independent analysis puts a QYB mazdutide lot at 95.1%, against 91.4% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
From vial to bench: what is recorded and what is assumed
What a laboratory can and cannot know about the provenance, storage history and representativeness of what lands on its bench.
Pass, conform, comply: three words for three different claims
Statements of conformity are supposed to rest on a stated decision rule. Almost nothing in this trade states one.
Check the vial, not the box
The interval between manufacture and analysis is the most under-read figure on the page, and the one most likely to matter by the time a vial is opened.
Independent analysis puts a ERP cagrilintide lot at 95.3%, against 91.4% on the certificate
The result is unremarkable. What the report omits is not.
VendorInvestigate result on a Shenzhen dulaglutide lot lands 1.9 points below the supplier’s figure
The supplier has not disputed the finding. It has not explained the gap either.
From vial to bench: what is recorded and what is assumed
Chain of custody, in a regulated setting, begins at sampling. Here it begins when the package arrives.
Set the threshold at a tenth of a per cent and the small impurities vanish
We work through a single chromatogram twice, under two integration conventions, and show where the difference comes from.
Pore size, particle size, and why peptides need the wide pores
A shallow gradient resolves impurities that a steep one runs into the parent peak. Both methods are legitimate; only one of them can see the small stuff.
What Medutest charges to answer the pyrogen question
The masking phenomenon known as low endotoxin recovery means a formulation can return a clean result while containing endotoxin the assay cannot see.
Independent analysis puts a CPC orforglipron lot at 95.2%, against 92.3% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.