We split six vials four ways and posted them
Two years ago we ran an anonymised version of this comparison and promised a named one. This is it, with every method printed in full.
Analytics — 2025
HPLC, mass spectrometry, and the certificate of analysis.
Independent analysis puts a GL Biochem liraglutide lot at 97.5%, against 93.6% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Medutest result on a Tianjin exenatide lot lands 2.1 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
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.
Independent analysis puts a SSA liraglutide lot at 96.5%, against 93.1% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
VendorInvestigate result on a Zhuhai survodutide lot lands 3.8 points below the supplier’s figure
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
Nought point nine eight of a dalton: the modification that hides in plain sight
Deamidation adds 0.98 daltons. On a low-resolution instrument at incretin molecular weights, that is inside the noise.
Sterility is not a percentage, which is the whole difficulty
Purity, content, identity, sterility and endotoxin are five separate determinations. A single sheet of paper carrying one of them is not evidence about the other four.
Independent analysis puts a WWB tirzepatide lot at 98.7%, against 94.6% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
Asparagine, glycine, and the two residues that decide a shelf life
An isoaspartate rearrangement changes the molecule and not the mass. A method that confirms identity by molecular weight alone will report it as the parent compound.
PeptideMeter result on a Zhuhai dulaglutide lot lands 3.7 points below the supplier’s figure
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Independent analysis puts a QSC mazdutide lot at 97.1%, against 93.6% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
The reviewer, the approver, and why regulated documents carry two names
Somebody has to be answerable for a release document. On most certificates in this market, nobody is named at all.
VendorInvestigate result on a Xi'an cagrilintide lot lands 0.7 points below the supplier’s figure
The report states the gradient, the wavelength and the integration threshold, which is more than most.
What twenty companies say about storage, and what they have measured
We asked twenty companies three questions about stability data and print every answer, refusal and non-response.
PeptideMeter result on a Zhuhai tirzepatide lot lands 3.5 points below the supplier’s figure
The result is unremarkable. What the report omits is not.
Independent analysis puts a SGN cagrilintide lot at 98.0%, against 96.6% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
Independent analysis puts a GL Biochem semaglutide lot at 97.8%, against 94.6% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
The retest date and the expiry date are not the same document
What would make a difference is not a regulator. It is three lines on a certificate, all of which are already known to whoever wrote it.
Why a 0.036-dalton difference is the hardest number in peptide identity
Calibration drift is real, unremarkable, and the reason serious laboratories run internal standards.