PeptideMeter result on a Chengdu exenatide lot lands 3.6 points below the supplier’s figure
The supplier has not disputed the finding. It has not explained the gap either.
Analytics
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Six words a verification badge would need to mean anything
A badge asserts that something was tested. It does not assert what, when, on whose sample, by what method, or whether the lot on sale is the lot that was tested.
What the paperwork is for, and who it was designed to protect
The header identifies the batch, the table records the tests, and the footer says who is answerable. Two of the three are usually incomplete.
VendorInvestigate result on a Qingdao retatrutide lot lands 3.6 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
Independent analysis puts a GL Biochem exenatide lot at 98.1%, against 96.5% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Freezing a reconstituted vial: the ice-water interface problem
At low concentrations a measurable fraction of peptide can adsorb to glass and plastic surfaces, and the loss is largest exactly where it is least expected.
The number at the bottom of the certificate
A purity percentage is the most quoted figure in the research-peptide trade and one of the least examined. We asked four laboratories to analyse the same vial and got four…
Independent analysis puts a WXT semaglutide lot at 98.0%, against 95.7% on the certificate
The result is unremarkable. What the report omits is not.
VendorInvestigate result on a Wuhan orforglipron lot lands 3.8 points below the supplier’s figure
The supplier has not disputed the finding. It has not explained the gap either.
A document, not a test: what a certificate actually is
The purity figure is the least informative line on a well-constructed certificate and the only line most buyers read.
Independent analysis puts a GL Biochem tirzepatide lot at 96.7%, against 95.9% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
PeptideMeter result on a Zhuhai cagrilintide lot lands 1.5 points below the supplier’s figure
The report states the gradient, the wavelength and the integration threshold, which is more than most.
How a release document is put together in a regulated plant
Nothing on this page is difficult. It is simply unfamiliar, and unfamiliarity is what makes a weak certificate look like a strong one.
Matrix, laser, needle: the plumbing that determines what you see
A brief and unromantic tour of the interface between a liquid sample and a vacuum.
VendorInvestigate result on a Changsha dulaglutide lot lands 3.5 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
Same material, different gradients, different answers
The Journal submitted split samples from single lots to three assay services, under names unconnected to this publication, and published each method alongside each result.
Independent analysis puts a SWB dulaglutide lot at 96.2%, against 95.6% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Twenty-eight days is a number from somebody else’s product
We set out what is known, what is inferred and what is simply assumed about the fortnight after a vial is opened.
Soft ionisation: the twenty-year-old trick that made peptide identity routine
A brief and unromantic tour of the interface between a liquid sample and a vacuum.
Four ways a peptide comes apart
Deamidation, oxidation, aggregation and hydrolysis account for nearly all of what happens to a peptide over time. Each has a characteristic residue, a characteristic…