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.
Janoshik Analytical
Page 2 of 7 of this archive, newest first.
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.
What a reference standard is, and what an in-house standard is not
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.
The submitted sample: the weakest link in the whole system
What a laboratory can and cannot know about the provenance, storage history and representativeness of what lands on its bench.
Counter-ion, water, salt: three masses with no chromatogram
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.
What a split-sample exercise can establish, and what it cannot
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
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.
Calibrated, qualified, accredited: three words that are not synonyms
System suitability is the set of checks demonstrating that the instrument and method were performing adequately when your sample was injected. It is recorded as a matter of…
Sending the same vial twice, under two names
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
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.
The badge is about a sample. The listing is about a product.
Lot-level verification with a public report is a real and achievable thing. It exists in this market, on a minority of listings.
Counter-ion, water, salt: three masses with no chromatogram
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…
Who chose the vial that was tested?
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 submitted sample: the weakest link in the whole system
What a laboratory can and cannot know about the provenance, storage history and representativeness of what lands on its bench.
What a split-sample exercise can establish, and what it cannot
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.
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.
The named comparison we promised two years ago
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.
How a claim degrades between the bench and the listing
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.
Pore size, particle size, and why peptides need the wide pores
Ion-pairing additives sharpen peptide peaks and suppress ionisation in the mass spectrometer, which is why the purity method and the identity method are often not the same…