bought a second-hand HPLC. worst best decision of my life. AMA
The title is the argument: bought a second-hand HPLC. worst best decision of my life. AMA. Here is the rest of it. Carryover from a previous high-concentration injection looks exactly like a small impurity. The blank injection is four minutes and it removes the ambiguity entirely. Mass spectrometry answers identity.…
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.
UV response is not uniform across species.
Disagreeing with this bit: that spread is ordinary inter-lab variance, not a disagreement about the material.
Correction: that is a tailing factor, not a plate count. Different diagnostics for different problems.
Gave the same trace to two people I trust and got two integrations about a point apart. That was the most educational afternoon I have had here.
This. A shoulder that does not baseline-resolve is a question, not a quantity.
area percent is relative to what the detector saw and nothing else
two labs, two gradients, two honest answers
Is that baseline drawn by the software or by hand?
report the method or do not report the number
Retitled: the original claimed a comparison the post does not actually make.
Resolution between two peaks depends on retention, selectivity and efficiency. A shallower gradient buys retention and usually resolution, at the cost of peak width and run time.
reproducibility beats resolution if you only get one of them
Resolution between two peaks depends on retention, selectivity and efficiency.
Agreed. And the corollary is that the method line on a certificate is not decoration, it is the number’s provenance.
214nm sees the peptide bond, 280nm sees the aromatics
What did system suitability look like on that sequence?