What Medutest can tell you about a vial by weighing its water
Water is a reactant in hydrolysis, a plasticiser that mobilises the amorphous matrix, and a carrier for everything else. All three matter.
Laboratory Notebook in 2024
Page 2 of 5 of this archive, newest first.
The certificate is silent on contamination, and it never claimed otherwise
Every certificate circulating in this market answers a question about molecules. Almost none answers a question about organisms, pyrogens, or the integrity of the seal.
Set the threshold at a tenth of a per cent and the small impurities vanish
Baseline placement under a tailing peak is a judgement call with a direct effect on the area. It is one of the few places where two competent analysts genuinely disagree.
What Sweden customs does to a parcel it has decided to examine
A gel pack has a finite thermal budget, and once it is spent the payload equilibrates with whatever is outside the box. The only question is how long that takes.
What “LC-MS: conforms” tells a reader, which is almost nothing
What the Journal asks for when it writes to a supplier about an identity claim, and how often it gets it.
What the trials monitored, and what that implies about routine practice
Timing is the whole of the post-cessation panel: draw it too early and it measures the treatment period.
What the trials monitored, and what that implies about routine practice
Timing is the whole of the post-cessation panel: draw it too early and it measures the treatment period.
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.
Peak capacity, and the honest measure of a separation
Column chemistry, particle size and pore diameter determine what the separation is capable of before the gradient is even programmed.
What the four services actually offer, test by test
We asked all four services what they can determine, on what timescale, at what price, and under what accreditation. The answers are printed in full.
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.
Two gradients, one sample, two purities
A shallow gradient resolves impurities that a steep one runs into the parent peak. Both methods are legitimate; only one of them can see the small stuff.
Which results should be repeated before they are investigated
What the pivotal programmes measured and how often, which is a more defensible template than most published monitoring schedules.
The cake is a record of the cycle that made it
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.
The four testing services and the study none of them can run
Storage instructions in this market are close to uniform and almost never accompanied by the study that would justify them. Uniformity is a sign of convention, not of…
The reference change value: the number that tells you whether a delta is real
The arithmetic of the reference change value, worked for the analytes that matter here.
Four ways a peptide comes apart
The sequence predicts the failure mode. A methionine predicts oxidation; an asparagine followed by a glycine predicts deamidation; a cysteine predicts disulphide scrambling.
Gauge, pain and flow rate
Gauge affects pain and flow rate rather than depth. A finer needle is more comfortable and slower, and with a viscous solution the difference is noticeable.
Collapse temperature, and the hour of the cycle where shelf life is lost
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.
Two sessions a week, and the evidence behind the prescription
The recommendation survives scrutiny. The reasoning offered for it frequently does not.