The named comparison we promised two years ago
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.
PeptideMeter
An independent peptide testing and verification service.
One method is one opinion
Aggregates dissociate in the mobile phase and are recorded as monomer. Only a size-based separation reports them.
The badge is about a sample. The listing is about a product.
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.
Disregard limits: what a regulated laboratory does with a tiny 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.
A purity figure is a numerator over a denominator, and both are choices
Regulated pharmaceutical practice has explicit reporting, identification and qualification thresholds. This trade has none, which is why a purity figure carries no…
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.
What orthogonal actually means, and what it does not
Aggregates dissociate in the mobile phase and are recorded as monomer. Only a size-based separation reports them.
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.
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.
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…
The badge economy, and what it is actually certifying
Every step between the laboratory report and the product page removes information, and the badge is the last step.
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.
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.
An interlaboratory comparison nobody had run
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.
Same material, different gradients, different answers
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.
Same material, different gradients, different answers
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.
Sending the same vial twice, under two names
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.
What orthogonal actually means, and what it does not
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…
An interlaboratory comparison nobody had run
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.
The generic peptide method, and what it was designed for
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.