What orthogonal actually means, and what it does not
The most useful single addition to any purity determination is a second separation under a different pH or on a different stationary phase, and the second-most useful is a…
Félix Oyarzún
Page 2 of 7 of this archive, newest first.
Archive — page 2
134 piecesNine parcels, nine loggers, and one uncomfortable set of traces
The compendial definitions of cold, controlled cold and controlled room temperature permit specified excursions, and knowing the permitted band is the difference between an…
An interlaboratory comparison nobody had run
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.
PeptideMeter result on a Tianjin liraglutide lot lands 4.0 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
Janoshik result on a Changsha tirzepatide lot lands 0.8 points below the supplier’s figure
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
Independent analysis puts a ERP tirzepatide lot at 98.1%, against 95.1% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
Date of analysis, date of manufacture, and the gap between them
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.
Two decimal places, one injection, no procedure
This piece takes the measurement apart into the decisions it is made of, because each decision moves the answer.
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.
Counter-ion, water, salt: three masses with no chromatogram
The most useful single addition to any purity determination is a second separation under a different pH or on a different stationary phase, and the second-most useful is a…
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.
The out-of-range flag is a statistical convention with a printer attached
A flag is a probability statement about a population. It is not a statement about the person holding the printout.
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.
Medutest result on a Chengdu cagrilintide lot lands 4.4 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
Why a dead-clean sterile filter can pass pyrogen straight through
Bacterial endotoxin is a heat-stable lipopolysaccharide from the outer membrane of Gram-negative organisms. It survives sterilisation, passes a sterilising filter, and is…
Pore size, particle size, and why peptides need the wide pores
Ion-pairing additives sharpen peptide peaks and suppress ionisation in the mass spectrometer, which is why the purity method and the identity method are often not the same…
HbA1c and its lag: what a result three months old is telling you
HbA1c integrates roughly three months of glycaemia with the most recent weeks weighted most heavily. Almost every misreading of it is a misreading of that weighting.
Independent analysis puts a CPC dulaglutide lot at 96.5%, against 94.8% on the certificate
The supplier has not disputed the finding. It has not explained the gap either.
Janoshik result on a Chengdu 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.
Medutest result on a Qingdao dulaglutide lot lands 1.4 points below the supplier’s figure
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.