[Method] the gradient everyone uses for sema and why it under-resolves the des-amido
the gradient everyone uses for sema and why it under-resolves the des-amido. It comes up every few weeks and the answer has not changed. The system suitability argument, since it comes up whenever somebody posts a number without one. Before the sample result means anything, the instrument has to be shown to be fit…
Do you have the mass, or only the UV trace?
Same view — reporting the gradient is what makes a result checkable rather than merely stated.
Careful — you are treating retention time as identity. Two things can co-elute and the trace will not tell you.
Correction: that is a tailing factor, not a plate count. Different diagnostics for different problems.
Agreed, and it is why FGP printing the column and gradient on the certificate is genuinely useful rather than decorative.
Retention time shifted 0.4 minutes and I assumed the worst. It was the column temperature.
Retention time shifted 0.4 minutes and I assumed the worst.
Disagreeing with this bit: that spread is ordinary inter-lab variance, not a disagreement about the material.
a shoulder is not an impurity until you can resolve it
Not convinced by that integration. Dropping the baseline there absorbs part of the shoulder into the main peak.
the column has a history and it shows in the peak shape
two labs, two gradients, two honest answers
axis labels or the trace is decoration
UV response is not uniform across species. At 214nm you are looking at the peptide bond, which is why it is the working wavelength for this class; at 280nm you only see tryptophan, tyrosine and phenylalanine.
What did system suitability look like on that sequence?