Why a 0.036-dalton difference is the hardest number in peptide identity
Every instrument specification quoted in an advertisement is a best case obtained on a calibration mixture, not on a submitted vial.
Independent testing
Page 20 of 27 of this archive, newest first.
The batch number is the only thing connecting the page to the vial
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.
What the nitrogen said
Peptide content is the number that tells you how much drug is in the vial. Almost nobody sells it, almost nobody buys it, and when we paid for it on nine vials the results…
Independent analysis puts a TFC mazdutide lot at 98.4%, against 95.9% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
Why a result on one vial says less than the trade needs it to
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.
The fourteen-day problem, and what it does to a commercial testing model
The absence of microbiological capability in this market is a commercial fact with a straightforward explanation, and it is worth understanding before blaming anybody for it.
VendorInvestigate result on a Suzhou liraglutide lot lands 4.2 points below the supplier’s figure
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Peak capacity, and the honest measure of a separation
Column chemistry, particle size and pore diameter determine what the separation is capable of before the gradient is even programmed.
Independent analysis puts a SGN survodutide lot at 96.5%, against 95.8% on the certificate
The result is unremarkable. What the report omits is not.
Before anything is weighed, the peptide has to be charged
A brief and unromantic tour of the interface between a liquid sample and a vacuum.
PeptideMeter result on a Guangzhou cagrilintide lot lands 3.7 points below the supplier’s figure
The result is unremarkable. What the report omits is not.
The question no chromatogram has ever answered
The Journal has read several hundred certificates from twenty companies. We set out what the documents actually cover, and what a reader is filling in from imagination.
The submitted sample: the weakest link in the whole system
A result on one vial generalises to a batch only if the vial was drawn in a way that makes it representative — and nobody records how it was drawn.
A certificate is a snapshot, and peptides do not stand still
A document is only as good as the chain that connects it to the material, and most chains here are two or three links longer than the paperwork admits.
How a claim degrades between the bench and the listing
Every step between the laboratory report and the product page removes information, and the badge is the last step.
Independent analysis puts a JEEP tirzepatide lot at 96.0%, against 92.6% on the certificate
The result is unremarkable. What the report omits is not.
What orthogonal actually means, and what it does not
An orthogonal method separates on a different physical principle, so that species co-eluting in the first are likely to resolve in the second. Two runs of the same method at…
LAL, kinetic chromogenic, recombinant factor C: three ways to the same figure
The limit for a parenteral product is calculable from the dose and the body weight in two lines. Almost nobody in this trade performs the calculation.
Two gradients, one sample, two purities
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.
Medutest result on a Changsha survodutide lot lands 4.3 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.