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.
Callum Brathwaite
Page 7 of 7 of this archive, newest first.
Archive — page 7
134 piecesSame 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.
How a correct calculation becomes a wrong dose
Almost every case involves a change — a new vial, a new syringe size, a new supplier — carried forward with an old number.
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.
Aggregation: the impurity your chromatogram dissolved before it looked
We describe each pathway in enough chemical detail to explain why it is invisible to the method the trade uses, because that is the part which has practical consequences.
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…
Low endotoxin recovery: the interference nobody looks for
The masking phenomenon known as low endotoxin recovery means a formulation can return a clean result while containing endotoxin the assay cannot see.
Quadrupole, time-of-flight, orbital trap: what each class can and cannot see
Every instrument specification quoted in an advertisement is a best case obtained on a calibration mixture, not on a submitted vial.
One column, one wavelength, one very large blind spot
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.
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.
Mass spectrometry answers a different question, properly
Where two methods disagree, the conservative convention is to report the lower figure. It is not universal, and whether a laboratory follows it belongs on the report.
A named analyst is the cheapest quality signal in this trade
What the Journal asks when a document arrives unsigned, and what the answers have been.
Lipohypertrophy, and the absorption it ruins
A rotation scheme that is too complicated will not be followed. We describe the simple ones that are.
D-amino acids are invisible to mass spectrometry, and that is the whole problem
Stereochemical inversion changes the molecule, changes its biology, and changes its mass by exactly nothing.