The named comparison we promised two years ago
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
PeptideMeter
Page 3 of 8 of this archive, newest first.
Blind duplicates: what happens when a laboratory does not know it is being watched
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
Why purity is the cheapest number to flatter
Peptide content, identity, aggregate burden, moisture and endotoxin are all more informative for some purposes. All of them cost more.
The badge is about a sample. The listing is about a product.
The Journal does not treat a badge as evidence and states so wherever it reports one.
Two analysts, one chromatogram, two answers
Chromatographic software does not integrate every fluctuation in the baseline. It applies a threshold, and the threshold changes the reported purity by amounts that matter…
The badge economy, and what it is actually certifying
A badge asserts that something was tested. It does not assert what, when, on whose sample, by what method, or whether the lot on sale is the lot that was tested.
How a claim degrades between the bench and the listing
Lot-level verification with a public report is a real and achievable thing. It exists in this market, on a minority of listings.
An interlaboratory comparison nobody had run
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.
What column temperature does to selectivity
We set out the parameters a method disclosure would contain, all of which are known to whoever ran the sample and none of which is commercially sensitive.
Same material, different gradients, different answers
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
We split six vials four ways and posted them
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.
Retention time is not identity
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.
Six words a verification badge would need to mean anything
The Journal does not treat a badge as evidence and states so wherever it reports one.
What a laboratory knows about the material it receives
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.
Six words a verification badge would need to mean anything
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 decimal places, one injection, no procedure
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 software decides what counts as a peak
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.
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.
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.
What column temperature does to selectivity
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.