[Meta] proposal — a flair for chromatogram posts
proposal — a flair for chromatogram posts — with the counter-argument included, because I find it fairly persuasive.
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.
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.
System suitability — repeat injections, tailing factor, plate count, RSD on area — is what tells you the instrument was fit for the measurement that day. Without it, the purity figure is unanchored.
Tell me where this is wrong. That is the useful part of posting it.
best — the order this archive was captured in
Mass spectrometry answers identity. UV purity answers relative quantity under the run conditions. A document with one and not the other is answering half the question, and the half it answers should be stated.
Area percent is the integrated area of your peak over the total integrated area at one wavelength on one gradient. Change any of those and the number changes without the sample changing.
What wavelength, and what was the gradient?
the column has a history and it shows in the peak shape
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.
Ran a blank after a high-concentration injection and found the carryover I had been calling an impurity.
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.
you cannot report to two decimals off that baseline
baseline choice is a decision, not a measurement
A shoulder that does not baseline-resolve cannot be quantified honestly. You can report it as an unresolved shoulder, which is useful information, or you can develop the method until it resolves.