Accuracy, precision and the tolerance nobody states
Parts per million sound impressive until they are converted into daltons at the molecular weight of the thing being measured.
Laboratory Notebook
Closer to the bench: what a laboratory panel measures and what a change in it means, reconstitution and stability data, bioburden and endotoxin, container closure integrity, and the tests a certificate usually omits.
Everything filed here
Two sessions a week, and the evidence behind the prescription
One randomised trial has combined a GLP-1 receptor agonist with supervised exercise. Its result is the single most useful piece of evidence in this area.
The imaging substudy is an afterthought in the protocol and the centrepiece of the debate
The composition data comes from imaging substudies enrolling a few score participants at selected sites. It is the best evidence available and it is thin.
One method is one opinion
Aggregates dissociate in the mobile phase and are recorded as monomer. Only a size-based separation reports them.
Two per cent water sounds like nothing and is not nothing
Residual moisture is measured routinely in regulated manufacture, is reported almost nowhere in this trade, and predicts long-term stability better than any other single…
The one randomised trial that combined an incretin with supervised exercise
Mass and function are different endpoints and training affects them differently. Most coverage treats them as one.
The convention nobody explains before handing over the vial
Insulin syringes are graduated in units on a convention that fixes 100 units to one millilitre. That convention says nothing about how much peptide is in a unit, and…
Vitamin D, adiposity, and a volume-of-distribution problem
Reduced intake is a plausible mechanism for deficiency. Reduced absorption is not, and the two are conflated in most of the advice.
The skeleton responds to load, and load is falling
The evidence base is one secondary analysis, several small studies and a large amount of extrapolation from bariatric surgery.
The word “confirmed” is doing an enormous amount of work on this certificate
The Journal’s standing position: a mass that matches is necessary evidence of identity and nowhere near sufficient.
Aseptic technique for people who were never taught it
A needle blunts on first use. Reuse is uncomfortable, and it is a documented contributor to lipohypertrophy.
Five things a purity figure cannot tell you
An orthogonal method separates on a different physical principle, so that species co-eluting in the first are likely to resolve in the second. Two runs of the same method at…
An error taxonomy for a market without a pharmacist
The recurring errors in this market are not exotic. They are a small set of arithmetic and reading failures, each capable of moving a dose by a factor of two or ten.
Carbon-13, and the reason a peptide has more than one mass
A peptide has a monoisotopic mass and an average mass, they differ by several daltons at this molecular size, and a certificate that does not say which it quotes cannot be…
We asked four laboratories for a sterility test. Here is what came back.
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.
System suitability: the five checks that make a run interpretable
Accreditation to the international competence standard covers the scope a laboratory has been assessed for, which is not necessarily the test you commissioned.
One vial, four weeks, and the data that does not exist
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.
What a diode array adds, and why the certificate never shows it
Non-chromophoric components — counter-ions, salts, some excipients — contribute mass to the vial and nothing at all to the chromatogram.
Benzyl alcohol is a preservative, not a sterilising agent
Bacteriostatic water contains benzyl alcohol at 0.9 per cent, which inhibits microbial growth in a preserved multiple-dose presentation. It does not sterilise a contaminated…
The skeleton responds to load, and load is falling
What the Journal would want measured before treating this as settled in either direction.