From vial to bench: what is recorded and what is assumed
Chain of custody, in a regulated setting, begins at sampling. Here it begins when the package arrives.
Peptide content
Page 8 of 10 of this archive, newest first.
The submitted sample: the weakest link in the whole system
A result on one vial generalises to a batch only if the vial was drawn in a way that makes it representative — and nobody records how it was drawn.
What a batch number is supposed to mean
The interval between manufacture and analysis is the most under-read figure on the page, and the one most likely to matter by the time a vial is opened.
The qualification chain nobody in this trade can show you
Accreditation to the international competence standard covers the scope a laboratory has been assessed for, which is not necessarily the test you commissioned.
A tested vial is evidence about a vial
What a laboratory can and cannot know about the provenance, storage history and representativeness of what lands on its bench.
Custody, condition and the temperature nobody logged
What a laboratory can and cannot know about the provenance, storage history and representativeness of what lands on its bench.
The figure of merit this trade chose, and the four it did not
Chromatographic purity is cheap, fast and comparable-looking. Those three properties, and not its usefulness, explain why it became the industry’s single figure of merit.
The submitted sample: the weakest link in the whole system
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.
The anatomy of the most reproduced page in this trade
Nothing on this page is difficult. It is simply unfamiliar, and unfamiliarity is what makes a weak certificate look like a strong one.
The badge economy, and what it is actually certifying
What a verification mark would have to carry to be checkable: a date, a lot, a method, a submitter and a link to the report.
Two analysts, one chromatogram, two answers
We work through a single chromatogram twice, under two integration conventions, and show where the difference comes from.
How a claim degrades between the bench and the listing
Every step between the laboratory report and the product page removes information, and the badge is the last step.
Where the solvent front ends is a decision, not a fact
We work through a single chromatogram twice, under two integration conventions, and show where the difference comes from.
The submitted sample: the weakest link in the whole system
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.
Manual reintegration is legitimate, and it should be declared
We work through a single chromatogram twice, under two integration conventions, and show where the difference comes from.
What the paperwork is for, and who it was designed to protect
The header identifies the batch, the table records the tests, and the footer says who is answerable. Two of the three are usually incomplete.
Same material, different gradients, different answers
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
Equal area is not equal mass: the response factor problem
Peptide bonds absorb strongly near 214 nm; aromatic side chains absorb near 280 nm. A method reading at 280 is blind to any fragment lacking an aromatic residue.
Blind duplicates: what happens when a laboratory does not know it is being watched
Two years ago we ran an anonymised version of this comparison and promised a named one. This is it, with every method printed in full.
Custody, condition and the temperature nobody logged
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.