HbA1c and its lag: what a result three months old is telling you
The assay is not the problem. The interpretation of a lagging integral as a current measurement is the problem.
Laboratory Notebook
Page 2 of 12 of this archive, newest first.
Page 2
Two ways to lift a peptide into a vacuum, and why the answer differs
The ionisation method determines the charge states you see, the adducts you must account for, and the modifications you might destroy in the process.
The skeleton responds to load, and load is falling
Weight loss reduces bone mineral density at load-bearing sites. Whether that translates into fractures in this population is unmeasured.
What happens to a stopper after the fourth needle
Particulate matter is the oldest quality attribute in injectable manufacture and the one a private buyer is best placed to assess without instrumentation.
Lipohypertrophy, and the absorption it ruins
Repeated injection into the same small area produces lipohypertrophy — thickened, rubbery subcutaneous tissue with blunted and erratic absorption. It is common, it is…
Aseptic technique for people who were never taught it
For licensed products the in-use period is established by stability data. For a peptide reconstituted at home there is no such data, and the honest answer is that nobody…
Measuring more frequently generates more flags and not more information
The argument for a baseline panel is that it makes every subsequent result interpretable. The argument against frequent monitoring is that noise accumulates faster than…
What a reference standard is, and what an in-house standard is not
Matching a retention time against a standard is evidence of consistency, not proof of identity. Two different species can elute at the same time on one method.
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…
Nine 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…
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.
Why SSA can be entirely straightforward and still tell you nothing about bioburden
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.
Counter-ion, water, salt: three masses with no chromatogram
Aggregates dissociate in the mobile phase and are recorded as monomer. Only a size-based separation reports them.
What the older diet-and-exercise trials found in the hip
The evidence base is one secondary analysis, several small studies and a large amount of extrapolation from bariatric surgery.
Monitoring intervals, and the case against measuring too often
Every additional analyte raises the probability of a flagged result and lowers the average information content of the panel.
Percentage of loss, absolute kilograms, and the sleight of hand between them
Both the reassuring reading and the alarming reading are supportable from the same tables. This piece sets out which is which.
What the upper limit of normal for ALT should be, and why it is not
What the renal and hepatic outcome programmes actually measured, and over what duration.
One measurement, twenty companies, forty compounds
The Journal has read several hundred certificates from twenty companies. The number is almost always there; the method behind it almost never is.
What freeze-drying actually removes, and what it leaves behind
Lyophilisation does not stop degradation. It slows every pathway by removing the solvent that most of them require, and the residue of solvent that remains sets the rate.
Same mass, different molecule: why identity by mass is not identity
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.