Why a result on one vial says less than the trade needs it to
Chain of custody, in a regulated setting, begins at sampling. Here it begins when the package arrives.
PeptideMeter
Page 7 of 8 of this archive, newest first.
Pore size, particle size, and why peptides need the wide pores
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.
Twelve minutes or forty: what gradient slope buys
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.
From vial to bench: what is recorded and what is assumed
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.
Set the threshold at a tenth of a per cent and the small impurities vanish
We work through a single chromatogram twice, under two integration conventions, and show where the difference comes from.
Pore size, particle size, and why peptides need the wide pores
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.
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.
Three services, one lot, and a spread of two and a half points
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
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.
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.
Five things a purity figure cannot tell you
Aggregates dissociate in the mobile phase and are recorded as monomer. Only a size-based separation reports them.
A tested vial is evidence about a vial
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.
We split six vials four ways and posted them
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
The number at the bottom of the certificate
A purity percentage is the most quoted figure in the research-peptide trade and one of the least examined. We asked four laboratories to analyse the same vial and got four…
The impurity hiding underneath the parent peak
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…
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.
A tested vial is evidence about a vial
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
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.