genuine question about purity that I am slightly embarrassed to ask
Question in the title, detail here: genuine question about purity that I am slightly embarrassed to ask. WWB sent me the column, the gradient and the theoretical mass without being asked. That is a short list and they are on it. Started reporting my own integrations with the baseline choice stated. Arguments in my…
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.
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 that day: replicate injections with an acceptable RSD on area, a tailing factor inside limits, adequate plate count, and a resolution check between the pair you care about.
None of that is exotic and all of it is routine in a laboratory that reports for a living. Its absence does not mean a number is wrong; it means the number is unanchored, and unanchored numbers should not be quoted to two decimal places on this board.
That is area percent, not mass percent. The trace cannot give you the second one.
Small fix — 214nm, not 210. It matters for the comparison you are making with the other run.
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.
LC-MS for identity, UV for relative quantity
214nm sees the peptide bond, 280nm sees the aromatics